ISSN 2186-7968

ELPH

ANNUAL REPORTTOHOKU UNIVERSITY

2017

Editor
MURAMATSU, Norihito
KIKUNAGA, Hidetoshi
MUTO, Toshiya
TOKIYASU, Atsushi

Research Center for Electron Photon Science
Tohoku University
1-2-1 Mikamine, Taihaku, Sendai 982-0826
Japan

Phone: +81, 22-743-3400
Fax:+81, 22-743-3402

Web site: http://www.lns.tohoku.ac.jp/

982-0826

仙台市太白区三神峯1-2-1
東北大学電子光理学研究センター
電話022-743-3400

Fax

022-743-3402

Preface
We are pleased to issue the ELPH Annual Report 2017 that covers scientific andtechnical activities carried out at Research Center for Electron Photon Science (ELPH),
Tohoku University in FY2017 (April, 2017 to March, 2018).
The ELPH has been a part of Joint Usage / Research Centers since FY2011. The
Joint Usage / Research Centers (JURC) system was engaged by the Ministry of
Education, Culture, Sports, Science and Technology (MEXT) to encourage and promotecollaborative research passing through the border of respective universities.
As one knows framework of joint research activity in Japan had been progressed
based on laboratories belonging to national universities before the incorporation in 2004.
The framework was refurbished to be a system of JURC officially accredited by theminister of MEXT in order to extract further research performance in 2008. The former“KAKURIKEN（核理研）” (Laboratory for Nuclear Science) became independent of
Faculty of Science in the end of 2009, and then ELPH was established in order to be amember of JURC. We, however, suffered from the incredible earthquake and Tsunami
occurred March 11, 2011, just before launch of JURC activity. Although the first two
years we spent the whole time to be recovered, the ELPH was fortunately re-approvedat the 6-year terminal evaluation and is now in the 2nd term of JURC activity.
Since the ELPH has been developing own research and education task based on thebasic natural science, it is unlikely to collaborate with industry use and so-called
innovative applicability. In order to obtain public comprehension, we have to explore
the interest of basic science and post the amount of scientific information. As a first step,“The ELPH Symposium” was held in March, 2018. The symposium is opened for every
ELPH users to overcome brick walls among the research fields. In addition, we invited
Prof. Eizo Nakamura, director of Institute of Planetary Materials, Okayama University.
Although different research filed, we have deeply impressed by his talk regarding
outstanding philosophy for education, research and laboratory management. We would
like to continue the ELPH symposium annually, and hope to create some fusedscientific fields.
We sincerely ask facility users and related scientific field communities forcontinuous supports and cooperation.
November, 2018
Director
Hiroyuki Hama

ELPH Annual Report 2017
Contents
I. Topics

The First ELPH Symposium as a Joint Usage / Research Center
N. Muramatsu

1

Winning Prizes in FY2017
T. Ishikawa, K. Nanbu, K. Takahashi, and Y. Honda

3

II. Papers

Study of dibaryons via γd→π0π0d at Eγ = 0.75–1.15 GeV
5T. Ishikawa, H. Fujimura, H. Fukasawa, R. Hashimoto, Q. He, Y. Honda, T. Iwata,
S. Kaida, H. Kanda, J. Kasagi, A. Kawano, S. Kuwasaki, K. Maeda, S. Masumoto,
M. Miyabe, F. Miyahara, K. Mochizuki, N. Muramatsu, A. Nakamura, K. Nawa,
S. Ogushi, Y. Okada, K. Okamura, Y. Onodera, K. Ozawa, Y. Sakamoto, M. Sato,
H. Shimizu, H. Sugai, K. Suzuki, Y. Tajima, S. Takahashi, Y. Taniguchi, Y. Tsuchikawa,
H. Yamazaki, R. Yamazaki, and H.Y. Yoshida
How to measure the ∆(1232) radius
9
H. Shimizu, Q. He, Y. Honda, T. Ishikawa, M. Miyabe, Y. Matsumura, N. Muramatsu,
A. Tokiyasu, Y. Tsuchikawa, and H. Yamazaki
Measurement of a photon transmittance at high intensity
15
Y. Matsumura, T. Ishikawa, Y. Honda, S. Kido, M. Miyabe, I. Nagasawa, K. Nanbu,
H. Shimizu, K. Takahashi, Y. Tsuchikawa, and H. Yamazaki
Current status of the FOREST/BLC experiments at ELPH
20
T. Ishikawa, K. Aoki, H. Fujioka, Y. Honda, T. Hotta, Y. Inoue, K. Itahashi, H. Kanda,
H. Kawai, K. Maeda, Y. Matsumura, M. Miyabe, S. Miyata, N. Muramatsu, T. Nishi,
H. Ohnishi, K. Ozawa, H. Shimizu, M. Tabata, A.O. Tokiyasu, Y. Tsuchikawa, andH. Yamazaki
Performance evaluation of Aerogel Cherenkov Counter with a refractive index of 1.10 for theΣp scattering experiment at J-PARC
25
K. Kobayashi, K. Miwa, R. Honda, Y. Akazawa, M. Ikeda, S. Ozawa, N. Fujioka,
A. Sakaguchi, Y. Nakada, H. Kawai, M. Tabata, H. Ito, A. Kobayashi, N. Kaneko,
T. Mizuno, T. Akaishi, K. Shirotori, M. Asano, S. Ashikaga, M. Ichikawa, M. Naruki,
T. Takahashi, K. Ozawa, and M. Sekimoto

Performance Evaluation of Silicon-Tungsten Electromagnetic Calorimeter Detector (ALICE
FoCal) and High Timing Resolution MRPC-TOF for High Energy Heavy Ion Experiment 47
R. Aoyama, T. Chujo, T. Hachiya, M. Hatakeyama, Y. Hoshi, T. Ichisawa, M. Inaba,
H. Kato, Y. Kawamura, D. Kawana, Y. Miake, T. Nonaka, K. Ozawa, S. Sakai, H. Sako,
T. Sakamoto, M. Shimomura, T. Sugitate, T. Suzuki, K. Tadokoro, M. Takamura, and
S. Takasu

Development of high-rate detectors by using MPPC for the charmed baryon spectroscopy
experiment at J-PARC
55
K. Shirotori, T. Akaishi, H. Asano, R. Honda, T. Ishikawa, Y. Ma, H. Noumi,
A. Sakaguchi, H. Sako, and T. N. Takahashi for the J-PARC E50 collaboration
Performance of a shower depth measurement method for the KOTO CsI calorimeter
68
N. Hara, K. Kotera, T. Mari, H. Nanjo, H. Nishimiya, Y. Sato, N. Shimizu, Y. Tajima,
T. Yamanaka
Search for an η’d bound state by use of the γd→ηd reaction
H. Fujioka, T. Ishikawa, and T. Sekihara

75

Development of an Aerogel Chrenkov Counter with Efficient Light Collection
H. Yamada, N. Morita, K. Matsuda, M. Okabe, and N. Muramatsu

77

Development of Electro-magnetic Sampling Calorimeter with Active Absorbers
83
Y. Hasegawa, H. Ishihama, H. Sato, T. Takeshita, R. Terada, Y. Yamashita, andY. Yoshimura
Influence of the Coulomb distortion on the measurement of the proton radius
T. Tamae and T. Suda

86

Light meson photoproduction off the proton at the SPring-8 BGOegg experiment
97
N. Muramatsu, J.K. Ahn, W.C. Chang, J.Y. Chen, S. Daté, T. Gogami, H. Hamano,
T. Hashimoto, Q.H. He, K. Hicks, T. Hiraiwa, Y. Honda, T. Hotta, Y. Inoue, T. Ishikawa,
I. Jaegle, J.M. Jo, Y. Kasamatsu., H. Katsuragawa., S. Kido, Y. Kon, S. Masumoto,
Y. Matsumura, K. Miki, M. Miyabe, K. Mizutani, T. Nakamura, T. Nakano, M. Niiyama,
Y. Nozawa, Y. Ohashi, H. Ohkuma, H. Ohnishi, T. Ohta, M. Oka, K. Ozawa, Y. Sada,
M. Sasagawa, T. Shibukawa, H. Shimizu, R. Shirai, K. Shiraishi, Y. Sugaya,
M. Sumihama, S. Suzuki, S. Tanaka, A. Tokiyasu, N. Tomida, N. Tran, Y. Tsuchikawa,T. Ueda, H. Yamazaki, R. Yamazaki, Y. Yanai, T. Yorita, C. Yoshida, and M. Yosoi
A trial to measure a spectral function of η’ mesons
103
H. Shimizu, Y. Matsumura, J. K. Ahn, W. C. Chang, J. Y. Chen, S. Daté, T. Gogami,
H. Hamano, T. Hashimoto, Q. He, T. Hiraiwa, Y. Honda, T. Hotta, T. Ishikawa, J. M. Jo,
Y. Kasamatsu, H. Katsuragawa, Y. Kon, S. Masumoto, K. Miki, M. Miyabe, K. Mizutani,
N. Muramatsu, T. Nakamura, T. Nakano, M. Niiyama, Y. Nozawa, Y. Ohashi, H. Ohnishi,
T. Ohta, M. Oka, K. Ozawa, C. Rangacharyulu, Y. Sada, T. Shibukawa, R. Shirai,
Y. Sugaya, M. Sumihama, S. Suzuki, S. Tanaka, Y. Taniguchi, A. Tokiyasu, N. Tomida,
N. Tran, Y. Tsuchikawa, T. Ueda, H. Yamazaki, R. Yamazaki, T. Yorita, C. Yoshida, andM. YosoiRadiochemical measurement of photonuclear reaction yields for photon activation analysis

111
Y. Oura, H. Terasaki, Y. Yamaguchi, T. Hara, J. Kaneko, N. Kuroiwa, I. Endo, and
Y. Miura

Identification of Elemental Composition and Preparation of Radio-tracer for Recovery of Rare
Metals in Household Garbage Incineration Slag by Photon Activation Method
117

K. Akiyama, K. Ito, S. Kubuki, and H. Kikunaga
Radioactive phantom productions for PET and β-ray imaging system
T Fukuchi, H. Haba, and H. Kikunaga

III. Status Report

121

Status of Accelerator Facilities in FY2017
Accelerator group

125

User Support Office Report in FY2017
M. Miyabe and User Support Office

129

Radiation Safety Report 2017
Radiation Safety Office132

IV. List of Publication

135

V. Members of Committees

155

VI. Approved Experiments

159

I. Topics

ELPH Annual Report, Tohoku University (2017)

The First ELPH Symposium
as a Joint Usage / Research Center
Norihito Muramatsu
Research Center for Electron Photon Science, Tohoku University, Sendai 982-0826
After the recovery from the Great East Japan Earthquake, the accelerator facilities
at Research Center for Electron Photon Sience (ELPH), Tohoku University, have beenstably operated and used by many internal and external researchers in wide scientificfields as a Joint Usage / Research Center (JURC). On 2 March 2018, the first symposium
was held for the purpose to share the research activities and achieved results of theindividual user programs using the ELPH facilities in FY2017. This symposium also
aimed to promote the paticipant's considerations about the JURC operation and thefuture direction of the facilities.
At the beginning of the symposium, the Director of ELPH, Prof. Hama, gave an
opening address with the explanation about the facility status and the activities as a
JURC. Scientific reports from several users then followed with open discussions for theiractivities and results. There were one talk from the field of accelerator development andsynchrotron radiation, four from nuclear and high energy physics, and two from theresearches using radioisotopes. Two special lectures were also arranged to discuss thefacility issues: the near future experiment of proton radius measurement at ELPH, given
by Prof. Suda, and the new challenges at the Institute for Planetary Materials, Okayama
University, by Director Prof. Nakamura.
The symposium was co-hosted by ELPH and the Users Association. At the final
session, a general meeting by the Users Association started from a greeting speech by
President Prof. Tamura, and continued the exchange of user's suggestions and requests
to the ELPH facilities and the other users. More than 50 people joined in the symposium
and shared a productive time. We plan to continue the ELPH symposium once per year
from now on.

1

2

Table 1

Program of the ELPH symposium for FY2017 (in Japanese).

=== 第一部 拠点シンポジウム ===9:30 センター長挨拶およびセンター拠点活動の概要
濱 広幸
東北大学 電子光理学研究センター
9:55 成果報告１（放射光・加速器）
山本 樹
高エネルギー加速器研究機構 放射光科学研究施設「極短周期アンジュレータの開発と東北大・試験線形加速器（t-ACTS）を用いた放射の評価実験」
10:20 成果報告２（原子核・高エネルギー）
大西 宏明
東北大学 電子光理学研究センター「ELPH におけるハドロン物理」
10:45
休憩
10:55 成果報告３（原子核・高エネルギー）
永尾 翔
東北大学 高度教養教育・学生支援機構「NKS2 を用いたストレンジネス光生成反応研究の成果と今後の展望」
11:20 成果報告４（原子核・高エネルギー）
本多 良太郎東北大学 理学研究科「GeV-γ実験室を利用したΣp 散乱実験（J-PARC E40）用の耐高計数 AC 検出器の性能評価」
11:45 成果報告５（原子核・高エネルギー）
西口 創
高エネルギー加速器研究機構 素粒子原子核研究所「ELPH 電子ビームを利用した高エネルギー物理実験用検出器開発 J-PARC COMET 実験での例」
12:10
昼食
13:30 成果報告６（RI 利用）
白崎 謙次
東北大学 金属材料研究所「電子光センターでの核種製造と溶媒抽出」
13:55 成果報告７（RI 利用）
福地 知則 理化学研究所ライフサイエンス技術基盤研究センター「次世代イメージング装置を用いた放射化分析」
14:20
休憩
14:30 特別講演Ⅰ
須田 利美
東北大学 電子光理学研究センター「ELPH での低エネルギー電子散乱による陽子電荷半径測定 ―Proton Radius Puzzle の解明・理解を目指して―」
15:20 特別講演Ⅱ
中村 栄三
岡山大学 惑星物質研究所「小規模研究所からの共同利用・共同研究拠点の新しい機能への挑戦」
16:10
休憩=== 第二部 利用者の会 ===16:30 会長挨拶
田村 裕和
東北大学 理学研究科
16:35 ユーザーオフィスからの報告
宮部 学
東北大学 電子光理学研究センター
16:45 ユーザー講演石川 貴嗣
東北大学 電子光理学研究センター「FOREST 実験の位置づけと将来の展望」
金田 雅司
東北大学 理学研究科「NKS2 グループからの要望」
菊永 英寿
東北大学 電子光理学研究センター「大強度電子線形加速器を利用する共同利用者・プラットホーム利用者のマシンタイム希望の現状」
17:30 総会（幹事 須田利美）
18:30 意見交換会・懇親会（研究棟１階 多目的室）

ELPH Annual Report, Tohoku University (2017)

Winning Prizes in FY2017
Takatsugu Ishikawa, Ken’ichi Nanbu, Ken Takahashi, Yuki Honda
Research Center for Electron Photon Science, Tohoku University, Sendai 982-0826
In FY2017, four staff members won the prizes at Research Center for Electron Photon
Science, Tohoku University.
Morita Memorial Award of the Senshu society (Takatsugu Ishikawa)
The leading role for the following achievements received recognition:1)

development of a high-intensity photon beamline including construction of a photontagging system and a profile monitor of the photon beam [NIM A622 (2010) 1],

2)

construction of main detectors consisting of electromagnetic calorimeters, FOREST
at ELPH [NIM A832 (2016) 108] and BGOegg at SPring-8/LEPS2 [NIM A837 (2016)109], for meson photoproduction experiments,

3)

study of hadrons with baryon number B=2 (dibaryon) via double neutral-meson
photoproduction on the deuteron [PLB 772 (2017) 398], and4)

recovery of the photon beamline and FOREST detector at ELPH from the 2011
earthquake, conducting a new generation experiment for the precise and accurate
determination of the scattering length between the eta meson and nucleon utilizing
a special kinematics.

Excellent Presentation Award in the Division of Engineering and Technical Staff(Ken’ichi Nanbu)
The electron accelerator complex, including a high intensity 60 MeV linac, a 90 MeV
injector linac, a 1.35 GeV BST (booster-storage) ring and a test accelerator, has been
operated for education and research works at ELPH. In addition, there are some large
dipole electromagnets for discriminating charged particles. Since these accelerators andexperimental apparatuses consume a large amount of electricity, the operating cost isgetting increased recently because of the increase in electricity charges. It is difficult to
reduce the electricity consumption, limiting the beam time due to the allocated operationbudget. Shortening the beam time has significant influence on the education andresearch. In this work, we improved management methods to reduce the cost for
operating the utilities such as an air conditioning system and an accelerator coolingsystem. The operating cost has been reduced successfully to maintain the beam time.

34

Technology Award in the Faculty of Science (Ken Takahashi)
The systems for RI manufacturing and real-time beam measurement were developed
to provide "safe experimental environment" and "qualified electron beam irradiation" tojoint users. For the RI manufacturing, the system was improved comprehensively fromboth aspects of hardware and software. The irradiation system with low exposure wasconstructed by adding more compact and sufficient radiation shielding performance andimproving a sample transporting device. The exposure of the user has been thus reduced
when replacing the sample. In addition, the system for real-time beam measurement
was developed with a current monitor, a space size monitor using a fluorescent screen
and a camera, etc. The measurement programs and the display methods were improved
so that users should be able to grasp the status of beam irradiation at all times.
New Face Award of Nuclear Physics Community (Yuki Honda)
Liquid metals were bombarded by a D3+ beam, and an unknown d+d reaction peculiar
to the molecular beam was discovered. We proposed "Cooperative colliding mechanism"(CCM): one deuteron is elastically scattered toward another deuteron in the same
molecule by the target metal nuclei, and causes a d+d reaction. The CCM explains theunknown d+d reaction quantitatively. Screening potentials of the d+d reaction in themetals were estimated to be very small with CCM, and it could be understood by theelectron screening effect. In addition, it was found that the CCM should affect past solid
metal experiments, and make misidentification of the screening potential of several
hundred eV.
Table 1
第 13 回森田記念賞
石川貴嗣

平成 29 年 11 月 11 日＠青葉サイエンスホール「光子ビームによるクォーク・ハドロン物理の探求」

総合技術部職員研修会
南部健一

Awards won by the ELPH staff in FY2017

優秀発表賞

平成 29 年 11 月 17 日＠片平さくらホール「電子光理学研究センターにおける加速器運転経費削減の取り組み」

理学研究科・理学部技術研究会 理学研究科技術賞

平成 29 年 11 月 28 日＠青葉サイエン

スホール
高橋健

「低被曝 RI 製造システムの構築とリアルタイム電子ビーム計測システムの開発」

原子核談話会新人賞
本多佑記

平成 30 年 1 月「Study of the low-energy d+d reaction in liquid Metals」

II. Papers

ELPH Annual Report, Tohoku University (2017)

5(ELPH Experiment : #2623, #2640, #2655, #2694, #2710)

Study of dibaryons via γd → π 0π 0d at Eγ = 0.75–1.15 GeV
T. Ishikawa1 , H. Fujimura1∗ , H. Fukasawa1 , R. Hashimoto1† , Q. He1‡ ,Y. Honda1 , T. Iwata2 , S. Kaida1 , H. Kanda3§ , J. Kasagi1 , A. Kawano4 ,S. Kuwasaki1 , K. Maeda3 , S. Masumoto5 , M. Miyabe1 , F. Miyahara1¶ ,K. Mochizuki1 , N. Muramatsu1 , A. Nakamura1 , K. Nawa1 , S. Ogushi1 ,Y. Okada1 , K. Okamura1 , Y. Onodera1 , K. Ozawa6 , Y. Sakamoto4 , M. Sato1 ,H. Shimizu1 , H. Sugai1∥ , K. Suzuki1∗∗ , Y. Tajima2 , S. Takahashi1 ,Y. Taniguchi1 , Y. Tsuchikawa1†† , H. Yamazaki1‡‡ , R. Yamazaki1 ,and H.Y. Yoshida2
1

Research Center for Electron Photon Science (ELPH), Tohoku University, Sendai 982-0826,
Japan
2

Department of Physics, Yamagata University, Yamagata 990-8560, Japan
3

4

Department of Physics, Tohoku University, Sendai 980-8578, Japan

Department of Information Science, Tohoku Gakuin University, Sendai 981-3193, Japan
5

6

Department of Physics, University of Tokyo, Tokyo 113-0033, Japan

Institute of Particle and Nuclear Studies, High Energy Accelerator Research Organization(KEK), Tsukuba 305-0801, JapanThe total and differential cross sections were measured for the γd → π 0 π 0 d reaction at incident

energies ranging from 0.75 to 1.15 GeV by using the FOREST detector at ELPH: the excitation functionof the total cross section, angular distributions of d and π 0 s, invariant-mass distributions for π 0 d andπ 0 π 0 . The main objective of investigating this reaction is to study isoscalar dibaryons in the π 0 π 0 dsystem and an isovector dibaryon in the π 0 d system. The deduced experimentally enable us to give
evidence not only for the 2.15-GeV/c2 isovector dibaryon but also for 2.47- and 2.63-GeV/c2 isoscalar∗

Present address: Department of Physics, Wakayama Medical University, Wakayama 641-8509, Japan†

Present address: Institute of Materials Structure Science (IMSS), High Energy Accelerator Research
Organization (KEK), Tsukuba 305-0801, Japan‡

Present address: Institute of Fluid Physics, China Academy of Engineering (CAEP), Mianyang 621900,
China

§

Research Center for Nuclear Physics (RCNP), Osaka University, Ibaraki 567-0047, Japan¶

Present address: Accelerator Laboratory, High Energy Accelerator Research Organization (KEK),
Tsukuba 305-0801, Japan∥

Present address: Gunma University Initiative for Advanced Research (GIAR), Maebashi 371-8511,
Japan

∗∗

Present address: The Wakasa Wan Energy Research Center, Tsuruga 914-0192, Japan††

Present address: Department of Physics, Nagoya University, Nagoya 464-8602, Japan‡‡

Present address: Radiation Science Center, High Energy Accelerator Research Organization (KEK),
Tokai 319-1195, Japan6
dibaryons. The details are described in a preprint [arXiv: 1805.08928 (2018)].

§ 1. Introduction

The study of the B = 2 systems (dibaryons) has a long history [1]. An early work by Dyson andXuong [2] predicts the sextet of non-strange dibaryons DIJ with isospin I and spin J (D01 , D10 , D12 , D21 ,

D03 , and D30 ) based on the first known dibaryon, deuteron (D01 ), the 1S0 -N N virtual states (D10 ), and aresonance-like structure at M =2.16 GeV/c2 for the 1D2 -pp amplitude (D12 ) of the partial wave analysis

for the π + d → pp reaction. The recent observation of the d∗ (2380) (D03 ) by the CELSIUS/WASA andWASA-at-COSY collaborations [3, 4] has made us pay attention to the classification. It is important toestablish the excitation spectrum of dibaryons in order to understand their internal structures and basic
building blocks of hadrons. A dibaryon is an interesting object to study its basic configuration from amolecule-like state consisting of two baryons (such as the deuteron) to a hexaquark hadron state, whichis expected to appear as a spatially-compact exotic particle.
Although the πd system has a resonance-like structure at approximately 2.15 GeV/c2 , the structure
can be also understood as a quasi-free (QF) ∆ excitation from a nucleon in the deuteron. Currently, any
experimental data are not recognized to show evidence for the existence of the 2.15-GeV/c2 resonance,d∗ (2150) corresponding to D12 . The d∗ (2150) is a key state to understand the sextet of dibaryons. In
photoinduced reactions, the γd→π 0 d reaction is a convenient approach to study d∗ (2150). Even if it isobserved, it can be also understood as a quasi-free (QF) ∆ excitation from a nucleon in the deuteronsimilarly to the π + d → pp and π ± d → π ± d reactions. The γd→π 0 π 0 d reaction is more advantageous tofind d∗ (2150) in the π 0 d subsystem because the QF ∆ excitation is kinematically separable as discussed

later. Thus, we study the γd→π 0 π 0 d reaction, aiming to observe isovector d∗ (2150) in the π 0 d systemthrough π 0 decay from a possible higher-mass isoscalar dibaryon in the π 0 π 0 d system.

§ 2. Kinematics

Possible mechanisms for the γd→π 0 π 0 d reaction can be classified in the following three:

1. QF π 0 π 0 production on a nucleon followed by deuteron coalescence (QFC),
2. the first π 0 is emitted from the QF nucleon, subsequently the N N (∆N ) reaction occurs withthe spectator nucleon to generate a dibaryon resonance, followed by the second π 0 and deuteronemission, and3. both the two π 0 s are emitted from a dibaryon resonance in a broad sense.
In the mechanisms 1 (2), the second π 0 should be emitted to compensate for the momentum given to the
QF participant nucleon by the first emitted π 0 to coalesce into a deuteron (a dibaryon resonance). Thus,
the angular distribution of deuteron emission becomes strongly backward (sideway) peaking for themechanism 1 (2). While the mechanism 3 makes a rather flat distribution. Since the three mechanisms
give completely different angular distributions, we can separate (or distinguish) the three mechanisms.

7§ 3. Results

The total and differential cross sections were measured for the γd→π 0 π 0 d reaction at the incident

energy ranging from 0.75 to 1.15 GeV [5–9] at the Research Center for Electron Photon Science (ELPH),
Tohoku University. The analysis of the γd → π 0 π 0 d reaction was made in the same way as in Ref. [10].

The excitation function of γd center-of-mass system Wγd is not monotonically increasing but shows
resonance-like behavior peaked at around 2.47 and 2.63 GeV. The angular distribution of deuteron emission is rather flat, and the kinematic condition for the obtained data completely differs from the QFC
and semi-QF processes. Thus, we consider the possibility that the resonance-like structure might be due
to a manifestation of dibaryons. In the observed reaction, both the two nucleons obviously participate
before emitting π 0 s.
The differential cross section dσ/dMπd as a function of πd invariant mass Mπd shows two peaks.
The centroid of the low-mass peak is ∼2.15 GeV/c2 independently of the incident energy. However, thatof the high-mass peak decreases with a decrease of the incident energy, and finally the two peaks are
merged into a bump. The high-mass peak reflects the appearance of the 2.15-GeV/c2 peak in dσ/dMπdbetween the other pion and deuteron (reflection). The resonance-like structure give a mass of 2.15±0.01
GeV/c2 with a width of 0.11±0.01 GeV/c2 . The angular distributions for the two π 0 s limit J π of thestate to 1+ , 2+ , or 3− . The 2+ assignment is consistent with the theoretically predicted D12 state, andwith the resonance structure of the 3P2 -πd amplitude.

§ 4. Summary

The total and differential cross sections have been measured for the γd→π 0 π 0 d reaction at inci-

dent energies from 0.75 to 1.15 GeV. The total cross section as a function of Wγd shows resonancelike behavior peaked at around 2.47 and 2.63 GeV. The experimental angular distributions of deuteronemission can never be understood in the QFC mechanism. The present work shows evidence for the
existence of the 2.15-GeV/c2 isovector dibaryon in the π 0 d channel, and of the 2.47- and 2.63-GeV/c2
isoscalar dibaryons in the π 0 π 0 d channel. The details including figures can be found in a preprint [arXiv:
1805.08928 (2018)].

Acknowledgments
The authors express their gratitude to the ELPH accelerator staff for stable operation of the accelerators in the FOREST experiments. They also acknowledge Mr. K. Matsuda, Mr. K. Nanbu, and
Mr. I. Nagasawa for their technical support. This work was supported in part by the Ministry of Education, Culture, Sports, Science and Technology, Japan through Grants-in-Aid for Scientific Research (B)No. 17340063, for Specially Promoted Research No. 19002003, for Scientific Research (A) No. 24244022,
for Scientific Research (C) No. 26400287, and for Scientific Research (A) No. 16H02188.

8

References[1]

H. Clement: Prog. Part. Nucl. Phys. 93 (2017) 195.

[2]

F.J. Dyson, N.-H. Xuong: Phys. Rev. Lett. 13 (1964) 815.

[3]

M. Bashkanov et al. (CELSIUS/WASA collaboration): Phys. Rev. Lett. 102 (2009) 052301.

[4]P. Adlarson et al. (WASA-at-COSY collaboration): Phys. Rev. Lett. 106 (2011) 242302.

[5]

T. Ishikawa et al.: JPS Conf. Proc. 10 (2016) 031001.

[6]

T. Ishikawa et al.: Nucl. Instrum. Meth. A 622 (2010) 1.

[7]

T. Ishikawa et al.: Nucl. Instrum. Meth. A 811 (2016) 124.

[8]

T. Ishikawa et al.: Nucl. Instrum. Meth. A 832 (2016) 108.

[9]

Y. Matsumura, T. Ishikawa et al.: Nucl. Instrum. Meth. A 902 (2018) 103.

[10] T. Ishikawa et al.: Phys. Lett. B 772 (2017) 398.

9

ELPH Annual Report, Tohoku University (2017)(ELPH Experiment : #2623, #2640, #2655, #2694, #2710)

How to measure the ∆(1232) radius
H. Shimizu1 , Q. He2 , Y. Honda1 , T. Ishikawa1 , M. Miyabe1 , Y. Matsumura1 ,N. Muramatsu1 , A. Tokiyasu1 , Y. Tsuchikawa3 , and H. Yamazaki4
1
2

Research Center for Electron Photon Science, Tohoku University, Sendai 982-0826

Department of Nuclear Science & Engineering, Nanjing University, Nanjing 210016
34Department of Physics, Nagoya University, Nagoya 464-8602

Institute of Particle and Nuclear Studies, KEK, Tsukuba 305-0801

A new method of measuring the ∆(1232) radius has been developed, detecting Bose-Einstein correlation effects in π 0 ∆ → π 0 π 0 N events obtained in GeV-γ experiments at ELPH. A three-dimensional

distribution of π 0 emitter sources is employed to extract the mean square radius of the ∆ resonance.

§ 1. Introduction

We have been discussing the application of π 0 π 0 Bose-Einstein correlation (BEC) to the measure-ment of the size of hadrons with a four-dimensional distribution of π 0 emitter sources [1]. It is possible to extract information on the space-time extension of a source from a space-like 2π 0 correlation function, which can be obtained experimentally by measuring a space-like momentum transfer Q[Q2 ≡ −(p1 − p2 )2 > 0] of each π 0 π 0 event having four-dimensional momenta, p1 and p2 [2]. However, thephysical meaning of the time component of the distribution is quite unclear. Therefore we return backto a three-dimensional distribution with which we can directly discuss the size of emitter sources.
In general, BEC effects may be expressed with two-particle correlation function CBEC (p1 , p2 ) as
CBEC (p1 , p2 ) =PBEC (p1 , p2 ).
P0 (p1 , p2 )(1)

Here PBEC (p1 , p2 ) denotes the probability density to find two identical bosons, subject to Bose-Einsteinsymmetry (BES), at r 1 and r 2 with momenta p1 and p2 , respectively, in three-dimensional space. The

p1 r1
x

y

p2

r2

Fig.1. Symmetrization of two identical π 0 ’s with respect to their originating points x and y.

10denominator P0 (p1 , p2 ) is another probability density of two identical bosons in the absence of BES. The
probability density PBEC (p1 , p2 ) is expressed as∫
PBEC (p1 , p2 ) = d3 xd3 y|ψ2 (p1 , p2 )|2 ρ(x)ρ(y)where ψ2 (p1 , p2 ) is a symmetrized two-particle plane wave function written by]1 [ψ2 (p1 , p2 ) = √ eip1 ·(r1 −x) eip2 ·(r2 −y) + eip1 ·(r1 −y) eip2 ·(r2 −x) ,
2

(2)

(3)

and ρ(x) represents a normalized emitter source distribution. Here x and y are the places where bosons
are emitted in the source. We have|ψ2 (p1 , p2 )|2 = 1 +1 −iq·(x−y)
1e+ eiq·(x−y) ,22with q = p1 − p2 . The probability density is then written by
]
[
∫
1
1
PBEC (p1 , p2 ) = d3 xd3 y 1 + e−iq·(x−y) + eiq·(x−y) ρ(x)ρ(y)22= 1 + |f (q)|2 ,by employing f (q), the Fourier transform of ρ(x),∫f (q) = d3 xeiq·x ρ(x),where ρ∗ (x) = ρ(x) is assumed. In this formulation, P0 (p1 , p2 ) is normalized to 1,∫
P0 (p1 , p2 ) = d3 xd3 y|ψ0 (p1 , p2 )|2 ρ(x)ρ(y)∫][1d3 xd3 y |eip1 ·(r1 −x) eip2 ·(r2 −y) |2 + |eip1 ·(r1 −y) eip2 ·(r2 −x) |2 ρ(x)ρ(y)=2∫= d3 xd3 yρ(x)ρ(y)
= 1,

(4)

(5)

(6)

(7)

and then the two-particle correlation function can be written by
CBEC (p1 , p2 ) = 1 + |f (q)|2 .

(8)

We assume 2π emissions take place in random phases at the emission points as indicated in the independent integration over x and y in (5).
It is necessary to show no q dependence of CBEC (p1 , p2 ) for the events having no BEC, although it is
not easy to find such a reference distribution without BEC. A two pion probability density distribution
P2 (p1 , p2 ) for π + π − events is a good candidate in principle for the reference distribution with no BEC.
For π + π − events, we have|ψ2 (π + : p1 , π − : p2 )|2 =]1 [ ip1 (r1 −x) ip2 (r2 −y) 2|ee| + |eip1 (r1 −y) eip2 (r2 −x) |22(9)since there is no BEC between π + and π − , in contrast to π 0 π 0 events which have to be symmetrized.
However it is difficult in practice to utilize the π + π − events to get the reference since experimental
setups and devices are in general rather different for π + π − detections from π 0 π 0 measurements. We
have been working on the development of a method to get the reference distribution with an eventmixing technique applying for experimentally obtained π 0 π 0 events [3].

11

§ 2. Gaussian type distribution

We employ a spherically-symmetric three-dimensional Gaussian type distribution ρ(x)
)
(
1
−x2
exp
ρ(x) = √2α2( 2πα)3

with a Gaussian parameter α. The Fourier transform of ρ(x) is then given by∫
f (q) = d3 xeiq·x ρ(x)
)
(
∫
1
−x2
3
iq·x
= √
d xe
exp
2α2
( 2πα)3)(∫1
α2 q 2(x − iα2 q)2= √d3 x exp −−2α22( 2πα)3
)
(
2 2
α q
.
= exp −
2
The integration over y can be performed likewise. Thus we have∫()
d3 xd3 yeiq·(x−y) ρ(x)ρ(y) = |f (q)|2 = exp −α2 q 2

(10)

(11)

(12)

and

2 2

CBEC (q) = 1 + |f (q)|2 = 1 + e−α q ,(13)where q = |q| is not a Lorentz invariant quantity but a three-dimensional momentum transfer. We
assume that the two-particle correlation function can experimentally be written by
2 2

CBEC (q) = 1 + λ|f (q)|2 = 1 + λe−α q ,(14)since all the events do not come from the process under consideration. Here λ (0 ≤ λ ≤ 1) is introduced

to describe chaoticity that measures the strength of the BEC effects.

§ 3. Application to π∆ processes

We discuss here an application of π 0 π 0 BEC effects to a size measurement of ∆(1232) using π 0 ∆events obtained in π 0 π 0 photoproduction at an incident photon energy around 1 GeV. In this process, π 0and ∆ are produced at the same time at first. Then the ∆ decays into π 0 N . If there is an overlap of the∆ and the first π 0 wave functions, some information on the size of ∆ is obtainable through π 0 π 0 BEC inthe ∆ rest frame under the following considerations.
1. π∆ system
We focus on a π∆ system no matter what its origin would be in the γN → π 0 ∆ → π 0 π 0 N reaction.

Experimentally, using a Dalitz plot of m2 (π 0 , p) versus m2 (π 0 , π 0 ), for example, we can select π∆events effectively.
2. Originating places of π 0
We restrict our considerations to quark-antiquark or three quark systems for hadrons. Then thesize of a baryon can be understood as the range of existence of quarks in the baryon. We assume
an energetic quark inside a hadron gives rise to meson emission as indicated in Fig. 2. It is clear

12
that the first π 0 and ∆ are produced at the same time in the γN → π 0 ∆ process, whether s-channel
resonance N ∗ takes place or not. It is difficult in general, however, to say the place where the π 0appears. But the momentum vectors of π 0 and ∆ can be traced back to the same space-time point
where an energetic quark Q was placed. The π 0 − ∆ system has a relative angular momentum of

q

π
N

N*

q

0

q

Δ

Q

q
q

q
q

q

q

q

γ
Fig.2. S wave meson emission due to an energetic quark.
0 (S wave) in the π 0 ∆ threshold region. It is natural to think that the wave functions of π 0 and∆ overlap each other at the origin of the π 0 ∆ system. Thus we assume that the first π 0 appears
somewhere within ∆ according to the quark distribution and then goes apart from the ∆, which
sequentially emits the second π 0 afterward.
3. Space-time coordinates
The space-time coordinates can be defined so that the center of ∆ is the origin of the coordinates,
O, when the first π 0 and ∆ appear simultaneously at τ = 0, where τ denotes the proper time at
the rest frame of ∆. In this space-time coordinate frame, the first and second π 0 s appear at A(0, x)
2nd

π0

Δ

B

y
O
1st

x

π0
A

Fig.3. Space-time coordinates of ∆ at rest.
and B(τ, y), respectively. We define the space-time coordinates like this for each π 0 π 0 event. Thus
we can get information of the ∆ size by measuring the BEC effects of π 0 π 0 events having momenta
p1 and p2 in the inertial frame of ∆ at rest, where the decay time τ does not give any effect in themeasurement as far as strong decay is concerned.

13
4. The definition of the size of ∆We assume one of the quarks becomes energetic in ∆ so as to emit a pion. The energetic quark Q
appears at y according to the quark distribution function ρ(y) in ∆. Once a decay process Q → q q̄+q

starts to emit a pion, the remaining three quarks form a nucleon so that the relative angularmomentum of the πN system becomes 1 (P wave) with the total momentum of zero as illustrated
in Fig. 4. The place of the pion traced back to the energetic quark gives a ”pion emitter source”

p2

Δ

N

q
Q
q

q 0
q π

q
-p2
q

q

Fig.4. ∆ → π 0 N decay originated by an energetic quark Q.
distribution corresponding to ρ(y) in the decay process of ∆ → π 0 N , in which the relative angularmomentum 1 has to be taken into account. Employing cylindrical coordinates y = (r, θ, z) with thez axis taken to be along the momentum vector p2 of π 0 decaying from ∆, we have
|2y × p2 | = 2rp2 = 1(15)

in the ∆ rest frame, where p2 = |p2 |.
Under these conditions, the reference distribution corresponding to Eq. (7) may be given by
)
(
∫
1
β≡
P0 (p1 , p2 ) = d3 xd3 y|ψ0 (p1 , p2 )|2 ρ(x)ρ(y)δ(r − β)
2p2
)
(
)
(
∫
2
2
−y
−x
1
exp
δ(r − β)d3 xd3 y exp
= √
2α2
2α2
( 2πα)6
)
(
∫
1
−y 2
δ(r − β)= √rdrdθdz exp
2α2( 2πα)3)(∫1
z2 + β2= √2πβdz exp −2α2( 2πα)3
)
(
β
β2
(16)
= 2 exp − 2 .
α
2α

14
And Eq. (2) becomes∫

d3 xd3 y|ψ2 (p1 , p2 )|2 ρ(x)ρ(y)δ(r − β)
]
(
)
(
)
[
∫
1
−x2
−y 2
1
1
exp
δ(r − β)= √d3 xd3 y 1 + e−iq·(x−y) + eiq·(x−y) exp
2
2
2α2
2α2
( 2πα)6
)
]
(
)
[
(
∫
−y 2
1
α2 q 2exp (iq · y) exp
δ(r − β)= √d3 y 1 + exp −22α2( 2πα)3
)
)
[
(
(
]
∫
α2 q 2
1−y 2
exp (irqr cos θ + irqz z)
δ(r − β) 1 + exp −= √rdrdθdz exp
2α22( 2πα)3)()(∫
z2 + β2β
α2 q 2dθdz exp −exp (iβqr cos θ + iβqz z)
exp −= P0 (p1 , p2 ) + √22α2( 2πα)3
)
)
(
(
β
β2
α2 q 2βexp −= 2 exp − 2 + √α
2α
2( 2πα)3) ∫ 2π(∫ ∞222(z − iβqz ) + β (1 + qz )·dz exp −dθ exp (iβqr cos θ)
2α2
−∞
0
)
(
)
)
(
(
β
β 2 (1 + qz2 )β2
α2 q 2β
exp −J0 (βqr ),(17)= 2 exp − 2 + 2 exp −
α
2α
α
2
2α2

PBEC (p1 , p2 ) =where q = (qr , 0, qz ) and J0 (x) denotes the 0th order Bessel function of the first kind. Therefore thecorrelation function may be written as)()(
β 2 qz2
α2 q 2exp −J0 (βqr )CBEC (q, p2 ) = 1 + λ exp −22α2(q 2 = qr2 + qz2 )(18)

for π 0 π 0 events in the γN → π 0 ∆ → π 0 π 0 N process. This correlation function depending on q and p2(= 1/(2β)) has to be measured in the frame of ∆ at rest to get the proper x distribution. The Gaussian
form factor given by (10) yields the BEC function (18), in which the BEC parameter α2 is experimentallyobtainable. Then the mean square radius of ∆ can be calculated as
)
(
∫
1
−x2
2
2
d3 x = 3α2 .
x exp⟨x ⟩ = √2α2( 2πα)3(19)

In this way, once we find the BEC parameter α2 by applying (18) to experimentally obtained π 0 π 0 data,
we can get the mean square radius ⟨x2 ⟩ of ∆(1232) given as 3α2 .

Acknowledgment
This work was supported in part by MEXT (Grant No. 19002003), and by JSPS (No. 24244022).

References[1]

Q. He et al., ELPH Annual Report (2011, 2012, 2013) 73.

[2]

H. Shimizu et al., ELPH Annual Report (2014) 22.

[3]

Q. He et al., Chinese Phys. 40 (2016) 114002; Prog. Theor. Exp. Phys. (2017) 033D02.

ELPH Annual Report, Tohoku University (2017)15(ELPH Experiment : #2776)

Measurement of a photon transmittance at high intensity
Y. Matsumura1∗ , T. Ishikawa1 , Y. Honda1 , S. Kido1 , M. Miyabe1 ,I. Nagasawa1 , K. Nanbu1 , H. Shimizu1 , K. Takahashi1 , Y. Tsuchikawa1† ,and H. Yamazaki1‡
1

Research Center for Electron Photon Science (ELPH), Tohoku University, Sendai 982-0826,
Japan

A transmittance monitor has been developed for the second tagged-bremsstrahlung-photon beamline at ELPH. The transmittance, which is defined as the probability of finding a photon arrival at thetarget position when a post-bremsstrahlung electron is detected with a photon-tagging counter, should
be determined to deduce cross sections for photoinduced reactions. The developed monitor consists ofa telescope of thin plastic scintillators with a positron and electron converter, and a dedicated circuit
implemented in a field-programmable gate array chip. The measured transmittance is found to be constant independently of the circulating electron current in the synchrotron. The details are described ina published paper [Y. Matsumura, T. Ishikawa et al., Nucl. Instrum. Meth. A 902, 103 (2018)].

§ 1. Introduction

Photoinduced reactions with the incident energy ranging from several hundred MeV to a few GeV

are important to study the structure of hadrons in detail. Meson photoproduction experiments havebeen conducted [1–5] with an electromagnetic-calorimeter (EMC) complex, FOREST [6], on the second
photon beamline [7] at ELPH. A bremsstrahlung photon beam is generated by inserting a radiator into
circulating electrons [7] in the electron synchrotron called Booster STorage (BST) ring [8]. The energyof each photon is determined by measuring the momentum of its corresponding post-bremsstrahlungelectron with a tagging detector system, STB-Tagger II [7]. The tagging signal does not always correspond to a photon arriving at the target for the meson photoproduction experiments. Thus, the photontransmittance (so called the tagging efficiency), which is defined as the probability of finding a photon
coming to the target position when an electron is detected with STB-Tagger II, should be determined todeduce cross sections for photoinduced reactions. The transmittance is experimentally measured since
it is difficult to incorporate all the conditions of circulating electrons in the calculation.
So far, we have measured the transmittance, Tγ , using a large SF5 lead-glass Cherenkov counter [9]on the photon beamline. The energy of a photon is measured with the counter in response to the tagging∗

Present address: Research Center for Nuclear Physics (RCNP), Osaka University, Ibaraki 567-0047,
Japan

†

Present address: Department of Physics, Nagoya University, Nagoya 464-8602, Japan‡

Present address: Radiation Science Center, High Energy Accelerator Research Organization (KEK),
Tokai 319-1195, Japan16
signal. The singles rate of the counter should be reduced so that it could work, namely the photonbeam intensity should be much lowered by decreasing the circulating current in the BST ring (faintbeam). We have developed a transmittance monitor for high-intensity photon beams at normal operation(circulating current of ∼ 20 mA and photon-tagging rate of ∼ 20 MHz), and confirmed the transmittanceis the same between the faint and high-intensity photon beams.

§ 2. Developed transmittance monitor

We used the same detector system for the photon-beam profile monitor with scintillating-fiber ho-

doscopes (BPM) [10]. BPM in this work consisted of a plastic scintillator (PS) for charge veto (Gv), an
aluminum-plate converter with a thickness of 0.5 mm, and two trigger PSs (Gt1 and Gt2). The thicknesses of the three PSs measured 1 mm each. Additional two layers of scintillating-fiber hodoscopes
to give the intensity map of the photon beam were not used. The condition of finding a photon by thisdetector system (BPM trigger) was
Tr = Gv ⊗ Gt1 ⊗ Gt2,

(1)

where ⊗ stands for coincidence of signals. The Gv signal rejected the events containing a charged particle
produced upstream, and the Gt1 and Gt2 signals required the events having an e+ e− pair. The discriminator thresholds for producing logic signals of Gv, Gt1, and Gt2 were set to 0.5Vmip , 1.5Vmip , and 1.5Vmip ,respectively. Here Vmip denotes the pulse height in response to the minimum ionizing particle.
A circuit to give Rγi for each tagging channel i has been implemented into a developed NIM module
called MPLM4. MPLM4 is a prototype of MPLM4X in Ref. [10] containing a field-programmable gatearray (FPGA) chip, Xilinx Spartan-6 [11]. MPLM4 (MPLM4X) accepts and produces NIM standard
signals through 36 (38) input and 18 output channels. The logical circuit has been designed using edgealigned signals with an internal 200-MHz clock signal. The Rγi is determined by the numbers, N s, ofthree signals for each tagging channel Tci:
Rγi =N (Tci ⊗ Tr) − N (Tci ⊗ Tr′ ),N (Tci)(2)where Tr’ denotes the 165-ns delayed signal for Tr, and the coincidence widths are the same between
Tci ⊗ Tr and Tci ⊗ Tr′ . The harmonic number of the BST ring with an RF frequency of 500.14 MHz is83 [8]. The 165-ns delay approximately corresponds to the time of a revolution in the BST ring. The
logic signals of Gv, Gt1, and Gt2 from the BPM detector, and those of 32 tagging channels out of 116 [7]are delivered to MPLM4.
The BPM detector itself is sensitive only to charged particles (e+ e− pairs) produced downstream of

Gv. This fraction (sampling ratio), ηγ , is proportional to the probability of finding a photon in the BPM
detector with respect to a tagging signal (BPM-response probability), Rγ . The actual photon transmittance, Tγ , can be determined from Rγ and ηγ :
Tγ =

Rγ
.
ηγ

(3)

Since Tγ is directly measured for a faint beam with an EMC module on the beamline, ηγ can be determined from the measured Tγ and Rγ values in the same condition. The sampling ratio, ηγ , was17determined using faint beams with tagging rates of 1 and 6 kHz. We describe the rate for all the tagging
signals simply as the tagging rate. The ηγ is found to be constant, and average values obtained are
0.00673 ± 0.00033 and 0.00662 ± 0.00020 for the 1- and 6-kHz tagging rates, respectively. These values

are consistent with the expected value of 0.00658 ± 0.00015(thr) ± 0.00022(mat) for the sampling ratio,
which is determined by a Monte-Carlo simulation based on Geant4 [12]. The errors 0.00015(thr) and

0.00022(mat) are given by the uncertainty of the effective discriminator threshold values (±20%) andthat of the material thickness covering each PS (±0.05 mm), respectively. Since the measured value of ηγ
includes the uncertainty of the material thickness, we have adopted the average value 0.00665±0.00017
with a systematic uncertainty of 0.00015 for the measured sampling ratio.

§ 3. Measurement of a transmittance at high intensities

We measured the BPM-response probabilities for the six circulating currents of 1, 2, 4, 8, 12, and

18 mA. Since the circulating currents given by a DC current transformer (DCCT) did not have enoughaccuracy, the ratio of the measured tagging rates were employed for that of photon intensities. The ratioof photon intensities for 1, 4, 8, 12, and 18 mA to the intensity at 2 mA were found to be 0.286 ± 0.010,

1.970 ± 0.022, 4.445 ± 0.045, 6.152 ± 0.062, and 9.535 ± 0.096, respectively. The actual currents of 1, 4,

8, 12, and 18 mA were approximately 0.6, 3.9, 8.9, 12.3, and 19.1 mA, respectively, if the circulating current of 2 mA was correctly measured. The counting efficiency of the BPM response for each circulating
current was estimated from singles rate of signals from BPM by using a Monte Carlo simulation which
incorporate finite widths and jitters of them. Since ηγ must be constant, the transmittance as a functionof the circulating current can be observed in the measured BPM-response probability. Fig. 1 shows theratio of BPM-response probability to that obtained in the 1-mA circulating current. The obtained ratios of the BPM-response probabilities have a constant value in a range from 0.95 to 1.05 including theresults from the faint beams. Thus, the measured transmittance for each tagging channel is constant independently of the circulating current (photon intensity). The actual transmittance, Tγi , can be obtained
dividing the BPM-response probability, Rγi , by the sampling ratio ηγ = 0.00665 ± 0.00017 ± 0.00015 andattenuation factor αatt .

§ 4. Summary

A photon-transmittance monitor has been developed for the second tagged-photon beamline at

ELPH. The developed monitor consists of the BPM detector and a dedicated circuit implemented in
MPLM4. The transmittance, Tγ , can be obtained from the response probability of the detector, Rγ ,and sampling ratio (the probability of e+ e− production with the converter), ηγ . The ηγ is determinedusing faint beams by comparing the Rγ and directly measured Tγ . The ηγ is found to be 0.00665 ±

0.00017(sta.) ± 0.00015(sys.). The Rγ can be successfully measured with this monitor for high-intensity

photon beams corresponding to 20 MHz tagging signals. The measured Rγ is found to be constant withrespect to the photon intensity for each photon-tagging channel within the statistical error (approximately ±5%). This suggests that Tγ is constant independently of the circulating current. The accuracy

18

1.5

1 kHz

6 kHz

1 mA

2 mA

4 mA

8 mA

12 mA

18 mA

Ratio Rγ /Rγ 1mA

1

0.5
1.5

1

0.5
0

100 0

100 0
Tagging channel

100 0

100

Fig.1. The ratio of response probabilities of BPM. The measured response probability, Rγ , isdivided by that for the circulating current of 1 mA. The three horizontal lines correspondto the ratio of 0.95, 1.00, and 1.05. The tagging rate of 1 kHz approximately corresponds
to the circulating of 1 µA.
of the transmittance measured at high intensity is expected to be ±5% owing to the uncertainty of ηγ .

The details are described in a published paper [Y. Matsumura, T. Ishikawa et al., Nucl. Instrum. Meth.
A 902, 103 (2018)].

Acknowledgments
The authors express many thanks to the ELPH accelerator staff for providing the primary electron
beam in stable condition. This work was supported in part by Grants-in-Aid for Scientific Research (A)No. 24244022, for Scientific Research (C) No. 26400287, and for Scientific Research (A) No. 16H02188.

References[1]

T. Ishikawa et al.: Phys. Lett. B 772, 398 (2017).

[2]

T. Ishikawa et al.: Proceedings of the XV International Conference on Hadron SpectroscopyHadron 2013, PoS(Hadron 2013)095;
T. Ishikawa et al.: Proceedings of the 10th International Workshop on the Physics of Excited Nucleons (NSTAR2015), JPS Conference Proceedings 10, 031001 (2016).

19
[3]

Y. Tsuchikawa et al.: Proceedings of the 12th International Conference on Hypernuclear andStrange Particle Physics (HYP2015), JPS Conference Proceedings 17, 062007 (2017).

[4]

T. Ishikawa et al.:Proceedings of the 26th International Nuclear Physics Conference,

PoS(INPC2016)267.
[5]

S.X. Nakamura, H. Kamano, T. Ishikawa: Phys. Rev. C 96, 042201 (R) (2017);
T. Ishikawa et al.: Acta Phy. Polon. B 48, 1801 (2017).

[6]

T. Ishikawa et al.: Nucl. Instrum. Meth. A 832, 108 (2016).

[7]

T. Ishikawa et al.: Nucl. Instrum. Meth. A 622, 1 (2010).

[8]

F. Hinode et al.: Proceedings of 11th International Conference on Synchrotron Radiation Instrumentation (SRI2012), Journal of Physics: Conference Series 425, 072011 (2013);
F. Hinode et al.: Proceedings of the 7th International Particle Accelerator Conference (IPAC2016),
p. 701.

[9]

A. Ando et al.: KEK report, KEK-79-21 (1979).

[10] T. Ishikawa et al.: Nucl. Instrum. Meth. A 811, 124 (2016).
[11] Spartan-6 website:⟨http://www.xilinx.com/products/silicon-devices/fpga/spartan-6.html⟩.

[12] S. Agostinelli et al.: Nucl. Instrum. Meth. A 506, 250 (2003);

J. Allison et al.: IEEE Transactions on Nuclear Science 53, 270 (2006);
Geant4 website ⟨http://geant4.cern.ch/⟩.

20

ELPH Annual Report, Tohoku University (2017)(ELPH Experiment : #2803, #2844, #2882)

Current status of the FOREST/BLC experiments at ELPH
T. Ishikawa1 , K. Aoki2 , H. Fujioka3 , Y. Honda1 , T. Hotta4 , Y. Inoue1 ,K. Itahashi5 , H. Kanda4 , H. Kawai6 , K. Maeda7 , Y. Matsumura1 , M. Miyabe1 ,S. Miyata8 , N. Muramatsu1 , T. Nishi5 , H. Ohnishi1 , K. Ozawa2 , H. Shimizu1 ,M. Tabata6 , A.O. Tokiyasu1 , Y. Tsuchikawa9 , and H. Yamazaki1
1Research Center for Electron Photon Science (ELPH), Tohoku University, Sendai 982-0826,
Japan

2

Institute of Particle and Nuclear Studies, High Energy Accelerator Research Organization(KEK), Tsukuba 305-0801, Japan
3

4

Department of Physics, Tokyo Institute of Technology, Tokyo 152-8551, Japan

Research Center for Nuclear Physics (RCNP), Osaka University, Ibaraki 567-0047, Japan
5

Nishina Center for Accelerator-Based Science, RIKEN, Wako 351-0198, Japan
6
7

Department of Physics, Tohoku University, Sendai 980-8578, Japan

8
9

Department of Physics, Chiba University, Chiba 263-8522, Japan

Department of Physics, University of Tokyo, Tokyo 113-0033, Japan

Department of Physics, Nagoya University, Nagoya 464-8602, JapanThe FOREST/BLC experiments are conducted to reveal the non-perturbative QCD phenomena. The
main objective at the first stage is to determine low-energy S-wave ηn scattering parameters using theγd → pηn reaction. The photon beam with energies around 940 MeV can give the recoilless conditionof η mesons by detecting the protons at 0◦ . The effects of the the final-state ηn interaction must be

enhanced due to the small relative momentum between the η meson and the residual neutron in thiskinematics. In this year, the physics data were collected from October 30 to December 2 in 2017. In thisreport, a brief summary of the first-stage FOREST/BLC experiment and collected data is described.

§ 1. Introduction

The nucleon resonance N (1535)S11 (simply described N ∗ below), a candidate for the chiral partnerof the nucleon N , is of particular importance. The interaction between an η meson and an N is important to study N ∗ since it strongly couples to ηN and lies near the ηN threshold. The low-energy ηNinteraction is described using the scattering length aηN and effective range rηN in an effective-range
expansion of the S-wave phase shift:k cot δ(k) =

1
aηN

+

1
rηN k2 + O(k4 ).
2(1)

The aηN values have been extracted using many theoretical analyses from the differential and total crosssections for the πN → πN , πN → ηN , γN → πN , and γN → ηN reactions. Although the imaginary

part of aηN (Im[aηN ]) concentrates ∼ 0.26 fm for different analyses, its real part (Re[aηN ]) scatters in awide range from 0.2 to 1.1 fm [1]. This uncertainty comes from the fact that the existing experimental

21
data do not include ηN scattering directly. We propose the γd → ηpn reaction to determine aηN at a
certain kinematics, which enhances the ηN scattering effect.

The incident photon bombards the proton in the deuteron and produces a virtual η meson with avery low momentum. Events are selected in which the incident energy is approximately 0.94 GeV and theproton is detected at 0◦ . The kinematics for these events satisfies the recoilless condition of the produced
η mesons. Thus, the ideal low-energy ηn scattering is expected to take place in this condition, where
the pn and ηp rescattering effects are suppressed due to their large relative momenta (∼ 0.94 GeV/c).
The sensitivity to the Re[aηn ] and Re[rηn ] values are investigated and summarized in Ref. [2] by using
a dynamical coupled-channel model [3, 4].

§ 2. Experimental setup

The γd → pηn reaction is measured at ELPH with the FOREST electromagnetic calorimeter sys-

tem [5, 6] together with an additional forward charged-particle spectrometer [7]. Fig. ?? shows theexperimental setup for the precise determination of aηn . The incident photon energy ranges from 0.82
to 1.26 GeV [8] for the circulating electron energy of 1.32 GeV in the electron synchrotron [9]. The detailsof the FOREST detector including the liquid deuterium target is described elsewhere [5]. The forward
scattered proton is momentum-analyzed with a bending magnet BLC (transported from the low-energy
ring of KEKB) behind FOREST. The trajectory of a charged particle is measured with 2 planar drift
chambers (DCs), and the time of flight is measured with 14 plastic scintillator (PS) hodoscopes (PSH+).
An additional e/π separation is made using 10 SF5 lead-glass Cherenkov counters (LGCs). Fig. 1 shows
the current experimental setup for the determination of aηn together with the geometry of the forward
spectrometer, and the placement of the detectors. The detectors are rotated by 15.7◦ with respect to thephoton beam direction so that ∼ 900-MeV/c protons are injected perpendicularly on the surface of thetwo DCs.

In this year, the physics data were collected in the two periods from October 30 to November 20(2017D) and November 23 to December 2 (2017E) in 2017. After commissioning in May 2017 [10],number of detectors for the forward spectrometer are increased. All the wires in the two DCs can be readout by fixing broken wires and increasing the number of RAINER boards from 6 to 10. The board includes
the amplifier-shaper-discriminator and time-to-digital converter functions, and accepts 32-channel input
signals. The number of active wires has become 272 from 175. Thanks to the dedicated detector frame,
the number of PSs are increased from 9 to 14, and that of LGCs are increased from 6 to 10. In the
2017E period, a small hodoscope consisting of 16 3-mm-width PSs (originally used for STB Tagger [11])is placed inside the BLC magnet to detect negative particles emitted at 0◦ . Accordingly, the circuitry is
modified slightly.
In commissioning in May 2017, the power supply for BLC, QC1LE, halted many times, indicating
the ground fault error, which was caused by the low resistance of cooling water together with the noisefrom the refrigerator for the cryogenic target. Ion-exchange resins are inserted in the cooling systems
at the GeV-γ building. From October 2017, BLC can be excited at normal operation with a coil current

22
PSs
DCs

a)

SF5 for e/π

z’

c)

40

z’=955 mm
FOREST

proton emitted at 0 deg

γγ

z’=763 mm
photon beam

Ν2forward proton spectrometerz’=653 mm

57
82

151

b)
4000
100

100

150

3500
z’

x’

3000

50

x’=1660 mm

37

z’=0 mmx’=0 mm

z (mm)

2500
515

339

2000
x’

113

1500

1000

500

0
+2000 +1500 +1000

+500

0

-500

-1000

-1500

x (mm)

Fig.1. a) Experimental setup at ELPH for the determination of aηn (from October in 2017).
The momentum and time of flight of the proton scattered at 0◦ are measured througha bending magnet. The forward emitted proton is momentum-analyzed with a bending
magnet behind FOREST. The trajectory of a charged particle emitted at 0◦ is measured
with two planar drift chambers, and the time of flight is measured with plastic scintillator
hodoscopes. Additional e/π separation is made using SF5 lead-glass Cherenkov counters.
b) Geometry of the forward spectrometer. The z axis is defined along the photon beam
direction in this panel. c) Placement of the detectors. The z ′ axis is rotated by 15.7◦ withrespect to the z axis.
of 1400 A. The magnetic flux By at the center was monitored with a nuclear magnetic resonance (NMR)
probe during the experiments, and By = 716.0 mT was adjusted by changing the coil current. Fig. 2
shows the magnetic flux By at the center for the 2017D and 2017E periods.
Unfortunately, one of our high-voltage (HV) power supply systems, LeCroy 1440, was out of order.
Many HV cables were rearranged within a newly introduced system, iSeg ECH 44A, and the otherexisting HV systems. Due to this trouble, we have some missing channels in the collected data in thisfiscal year.

§ 3. Collected data

The physics data with the deuterium and hydrogen targets were collected in the 2017D period, andthose with the hydrogen target were collected in the 2017E period. The BST ring was operated with acirculating energy of 1.3 GeV, a current of approximately 20 mA, and an RF frequency of 500.14 MHz.
It should be noted that the frequency was 500.18 MHz before the 2011 earthquake. Table 1 summarizes
the number of spills and events of the collected data in this fiscal year (2017). The statistics for the716.15716.15

716.1

716.1

716.05716

716
715.95

715.9

715.9

715.85715.85
0

2.5

5

7.5

10
12.5
time (day)

15

17.5

20

Dec 02

Dec 01

Nov 30

4
time (day)Nov 29Nov 28

Nov 25

Nov 24

Nov 232716.05715.95715.8

Nov 27716.2

Nov 26716.2

Nov 22

Nov 20

Nov 19Nov 18

Nov 17

Nov 16

Nov 15

Nov 14

Nov 13

Nov 12

Nov 11

Nov 10

Nov 09

Nov 08

Nov 07

Nov 06

Nov 05

Nov 04

Nov 03

Nov 02

Oct 31

716.25B (mT)

B (mT)

716.25

Nov 01

23

715.8

-2

0

6

8

Fig.2. Magnetic flux By at the center for the 2017D (left) and 2017E (right) periods measured
with an NMR probe. The horizontal solid lines correspond to the magnetic flux values
increased by ±0.001%, ±0.01%, ±0.02% from the central value 716.00 mT.
hydrogen data is similar to that for the 2009D period, and that for the deuterium data is only a third.
The data analysis is on-going to select coincidence events between the STB-Tagger II, FOREST, and BLC
detectors
Table 1. Numbers of spills and events collected in this fiscal year (2017). The circulating electronenergy of the BST ring was 1.3 GeV. The targets used were liquid hydrogen, deuterium,and empty.
period2017D
2017E

hydrogen#spills#events
46.26 k 397.30 M
26.42 k 198.36 M

deuterium#spills#events
31.95 k 309.83 M
—
—

empty
#spills #events
3.91 k 19.84 M
10.05 k 49.74 M§ 4. Summary

The first-stage FOREST/BLC experiment, aiming at the determination of the low-energy ηN scat-tering parameters Re[aηN ] and Re[rηN ], started from October 30 in 2017. The number of collected
events for the deuterium target is 0.3 G. We continue to collect data in a few years to determine Re[aηN ]with an accuracy of 0.1 fm.

Acknowledgments
The authors give thanks to the ELPH accelerator staff for their great efforts in the stable operationof the electron synchrotron. They deeply acknowledge S.X. Nakamura and H. Kamano for giving us
the predictions for the ηn rescattering effect in the proposed γd → pηn experiment. This work was

supported in part by Grants-in-Aid for Scientific Research (A) (24244022), for Scientific Research (C)(26400287), and for Scientific Research (A) (16H02188).

24

References[1]

Q. Haider and L.C. Liu: Int. J. Mod. Phys. E 24, 1530009 (2015);
and references therein.

[2]

S.X. Nakamura, H. Kamano, and T. Ishikawa: Phys. Rev. C 96, 042201 (R) (2017).

[3]

A. Matsuyama, T. Sato, T.-S.H. Lee: Phys. Rep. 439, 193 (2007).

[4]

H. Kamano et al.: Phys. Rev. C 88, 035209 (2013).

[5]

T. Ishikawa et al.: Nucl. Instrum. and Meth. A 832, 108 (2016).

[6]

T. Ishikawa et al.: Phys. Lett. B 772, 398 (2017);
T. Ishikawa et al.: PoS (INPC2016) 267;
T. Ishikawa et al.: PoS (Hadron2013) 095.

[7]

T. Ishikawa et al.: Acta. Phys. Polon. B 48, 1801 (2017);
T. Ishikawa et al.: JPS Conf. Proc. 13, 020031 (2017);
T. Ishikawa et al.: JPS Conf. Proc. 10, 031001 (2016).

[8]

T. Ishikawa et al.: Nucl. Instrum. and Meth. A 622, 1 (2010);
T. Ishikawa et al.: Nucl. Instrum. and Meth. A 811, 124 (2016);
Y. Matsumura, T. Ishikawa et al.: Nucl. Instrum. and Meth. A 902, 103 (2018).

[9]

F. Hinode et al.: J. Phys. Conf. Ser. 425, 072011 (2013).

[10] T. Ishikawa et al.: ELPH Annual report 2016, 11 (2017).
[11] H. Yamazaki et al.: Nucl. Instrum. Meth. A 536, 70 (2005).

ELPH Annual Report, Tohoku University (2017)25(ELPH Experiment : #2838 and #2858)

Performance evaluation of Aerogel Cherenkov Counter witha refractive index of 1.10 for the Σp scattering experimentat J-PARC
Kazuya Kobayashi1 , Koji Miwa2 , Ryotaro Honda1∗ , Yuya Akazawa2 ,Michihiko Ikeda2 , Shotaro Ozawa2 , Norina Fujioka2 , Atsushi Sakaguchi1 ,Yoshiyuki Nakada1,4 , Hideyuki Kawai3 , Makoto Tabata3 , Hiroshi Ito3 ,Atsushi Kobayashi3 , Naomi Kaneko3 , Takayuki Mizuno3 , Takaya Akaishi1 ,Kotaro Shirotori5 , Mitsuhide Asano5 , Sakiko Ashikaga6 , Masaya Ichikawa6 ,Megumi Naruki6 , Tomonori Takahashi5 , Kyoichiro Ozawa8 ,and Michiko Sekimoto7
1

Department of Physics, Osaka University, Toyonaka, 560-0043

2

Department of Physics, Tohoku University, Sendai, 980-8578
3

Department of Physics, Chiba University, Chiba, 263-8522
45Japan Atomic Energy Agency (JAEA), Tokai, 319-1184

Research Center for Nuclear Physics (RCNP), Osaka University, Suita, 567-0047
6

Department of Physics, Kyoto University, Kyoto, 606-8502
7

8

RIKEN, wako, 351-0198

High energy Accelerator Research Organization (KEK), Tsukuba, 305-0801

We developed an Aerogel Cherenkov Counter (AC) with an index of 1.10 for a Σp scattering experiment at J-PARC which was used to veto π particles of momentum range up to 1.4 GeV/c. The size of AC
was 480 (H) × 400 (V) × 80 (T) mm3 which was determined from a geometrical condition of a magnetic

spectrometer (KURAMA spectrometer). In order to obtain detection efficiency more than 98%, we selected radiator index of 1.10 which was rather high index as an Aerogel and totally 12 fine-mesh PMTs
were used to collect enough photons. The other requirement is that this AC should keep the efficiency
under the high single rate condition up to 300 kHz which is the expected value in the Σp scatteringexperiment. From the performance test experiment at ELPH, the mean photon electron number was
obtained to be 23 for e+ beam of 400 MeV. The efficiency was obtained to be 98% for 300 kHz beam rateby setting the threshold to be 3 photo electron.

§ 1. Introduction

One of the most important purposes of strange nuclear physics is to investigate the Baryon Baryon(BB) interaction. This is because the BB interaction is the basic interaction to describe a system including hyperons such as hypernuclei and high density matter in neutron stars. The understanding of the
BB interaction also becomes a key to understand the origin of the short range repulsive cores in nuclear∗

Present address: Department of Physics, Tohoku University, Sendai, 980-8578

26
force and the BB interaction. In order to investigate ΣN interaction, we proposed a Σp scattering experiment (J-PARC E40) to measure differential cross sections of the Σ+ p, Σ− p elastic scatterings andthe Σ− p → Λn inelastic scattering in the momentum range of 400 < p (MeV/c) < 700. The physics

motivation is to verify the large repulsive force due to Pauli effect in the quark level in the Σ+ p channel.
We also investigate the ΣN interaction systematically by separating isospin channels.
In the experiment, we detect two successive reactions of the Σ production by the πp → K + Σ re-action and the Σp scattering with magnetic spectrometers (the KURAMA spectrometer) and recoiled
proton detector (CATCH), respectively. Figure 1 shows the experimental setup of the E40 experiment.
One of the experimental key points is that we have to accumulate more than 107 Σ particles, to determine the differential cross section by detecting more than 10,000 scattering events. The KURAMA
spectrometer is a suitable spectrometer because it has large acceptances of 4% and 7% for Σ− and Σ+ ,respectively, and has a quite short flight length of ∼3 m to keep a survival rate of K + . However, in orderto perform experiment within a reasonable beam time of a few weeks, a high intensity π beams of 20
M/spill (1 spill is 2 seconds beam duration with 6 seconds cycle) should be used. In order to accumulateΣ particles effectively with 20 M/spill π beam particles, the trigger system is quite important. Especially,outgoing π particles can make dummy triggers. From the spatial constraint, an AC counter should beplaced between the yoke and the end guard of the KURAMA magnet where the fringing magnetic fieldof 0.4 T is expected with magnetic field excitation of 0.75 T. In order to keep a reasonable trigger rate
less than 10 k/spill, the AC counter is required to have an efficiency more than 97%. In order to satisfy such requirements, we developed AC counters with an index of 1.10. In this development process,we take a two-step way. In the first step, we optimized the transparency of the AC radiator and thereflection method, that is, mirror reflection or diffuse reflection with a small prototype detector. Afterthe optimization, we developed the actual AC counter. At each stage, the performances of the detectors
were checked with a positron beam in the test beam line at Research Center for Electron Photon Science(ELPH), Tohoku university.
In this annual report, we report the result of the performance check of the AC counters.

§ 2. Design of AC counter

The basic design of the AC counter was determined from the spatial condition. The AC countershould be installed between DC1 and SCH as shown in Fig. 1. The thickness of the AC counter was
limited to be less than 80 cm. The horizontal and vertical sizes were determined to be 480 mm (H) × 400

mm (V) to cover the hit profile of charged particles at the AC position. Fig. 2 shows the design of the AC
counter. The orange ellipse in Fig. 2 shows the rough beam envelope. Because the beam intensity is 20
MHz/spill (10 MHz) and the AC detector can not work under such high intensity, the AC was designed
to have a beam hole not to cover the beam region. However, the expected singles rate was still as highas ∼900 kHz in total. Therefore we divided the AC counter into four rooms which were also shown in

Fig. 2. The room1 and room2 are the same structure and these rooms are placed at the upper and lower
sides of the beam region. These rooms are read with a single PMT. The room 3 are placed at right side

27
DC3

TOF

DC2

Top View
SFT

DC1
AC
CH

Κ+

BC4

BC3

BH2

π+ beam

CFT + LH2

S-2S D magnet
position00.5

Tracker For
Beam region

1m

Beam Veto

TOF

Side View
DC2
BC3

BC4

CFT + LH2

DC3

SFT
DC1
AC CH

Fig.1. Experimental setup of the E40 experiment. Both horizontal and vertical views are shown.
The AC counter is shown as AC which is sandwiched by DC1 and CH. The size of AC isdetermined to have enough acceptance for the charged particle at this position

Front view

Side view
80

480

75

330

Room 3

Room 4185

75

2.5 inch fine-mesh PMTyBeam region

One piece of AC radiator

100
Room 2

100

x

185

z
(beam direction)

400

Room 1

Partition

Fig.2. Realistic drawing of the AC counter. The orange ellipse shows the rough beam envelope.
The AC counter is divided to 4 rooms to reduce the single rate for each room. The index of
the aerogel is 1.10 and 12 fine-mesh PMTs are used to readout photons from the aerogel
radiators.

of the beam region and two PMTs are attached at top and bottom side of the room. The room 4 is thefarthest from the beam region and has a large region because the singles rate is much lower. The singles
rates for each room are 300 kHz for room 1, 2 and 250 kHz and 40 kHz for room 3 and 4, respectively.

28
Photons from radiator are collected by 12 fine-mesh PMTs with a diameter of 2.5 inch which were usedin the Belle experiment.
We ask Chiba university group to make an aerogel radiator. They have a skill to make aerogels witha large refraction index more than 1.05 which is the largest index commercially available. They can also
make a high transparency type of radiator in addition to a normal transparency type [1] [2]. In order tomaximize the photon number, we performed a simulation study with GEANT4 by changing the index ofradiator and its transparency type. We also studied by changing the thickness of the radiator to optimize
the ratio between the radiator thickness and the air region. For example, if the radiator thickness is 30
mm, the air region thickness is 50 mm, because the total length is 80 mm. We also compared the photon
numbers for two reflection types, that is, mirror reflection and diffuse reflection. In this simulation, we
took into account the scattering length of the radiator, the quantum efficiency of PMT and reflectivity of
the reflector and so on. On the other hand, we could not measure the absorption length of the aerogel
which was necessary in the simulation. In this simulation, we used a scaled value of the scattering
length with a factor of 10 conservatively. Figure 3 shows the dependence of the obtained mean photon
number by changing the refraction index (n=1.06∼1.10), the transparency type and the thickness of the
air region, that is, thickness of the radiator. As expected, the larger photon numbers were obtained forthe high transparency type compared to the normal transparency type. As for the dependence of theradiator and air thickness, there were two trends. For the lower index such as n=1.06, the dependence
for the radiator and air thicknesses was small and the maximum photon number was obtained for the
air thickness of 30 mm and the radiator thickness of 50 mm. In the lower index radiator, the photon
number emitted in unit length was smaller. Therefore the long thickness of the radiator was necessary.
The scattering length and the absorption length were relatively longer and the effect of the absorption
or scattering of the photon in the radiator was relatively small. From these two factors, the maximum
photon was obtained in this condition for n=1.06. On the other hand, for the higher index such as n=1.10,
the maximum photon number was obtained for the air thickness of 50 mm and the radiator thicknessof 30 mm. In this index, the photon number emitted in unit length was larger and the scattering andabsorption lengths were relatively short. The effect of the absorption or scattering of the photon in theradiator was relatively large. Therefore, the maximum photon number was obtained in this condition,that is, smaller radiator thickness of 30 mm and the larger air thickness of 50 mm. In the middle
index such as n=1.08, the obtained photon number was minimum. This reason could be also understoodfrom these two factors. The photon number was still relatively small and the scattering length was also
relatively short. Therefore the obtained photon number was small. From these studies, we decided touse the radiator of n=1.10 and the configuration of the radiator and air thicknesses was determined to
be 30 mm and 50 mm, respectively. As for the transparency type, the clear type is expected to be muchbetter. However, the uncertainty of the absorption length is large. Therefore this should be checked witha beam. We also studied the reflection type between the mirror reflection and the diffuse reflection witha teflon. The maximum photon was obtained for the mirror reflection with the mirror plate at the centerregion of the AC counter. The mirror plate angle was optimized to maximize the photon yield and was29determined to be 60 degrees where the emitted photon could arrive at PMT with the single reflection at
this mirror. Finally, we determined the design of the AC counter as shown in Figure 2. Cotton strings
are placed at the back side of the radiators to prevent the radiators from falling down to the air region.
In order to the finalize the AC counter, at first, we constructed two prototype counters corresponding
to room 1, 2 with a mirror reflection and diffused reflection to compare these performances. Then we
performed a test experiment using a positron beam at ELPH.

Fig.3. Air thickness (aerogel thickness) dependence for photo-electron yield from a Geant4 simulation. The aerogel thickness is expressed as ”80 mm − (Air thickness)”. The open
triangle points show the results for the high transparency type.

§ 3. Performance test of the prototype counters
3.1 Prototype counters

We constructed the prototype counters with the same structure with room1, 2 which size of the
prototype counter was 75 (H) × 185 (V) × 80 (T) mm3 . One PMT was attached at the top of the counter.
In order to compare the performance for different reflection method, we fabricated one AC counter withthe mirror reflection (AC1) and one AC counter with the diffused reflection (AC2).
• AC1 (mirror reflection)

AC1 has a mirror reflation. As for the reflector we selected the MetalumyTM sheet which wasmeasured to have a larger reflectance with a thin sheet from previous research [3]. A reflection mirror
with a tilt angle of 60 degrees was set to guide the Cherenkov radiated photon to PMT with a single
reflection. The tilt angle was optimized for 1.3 GeV/c π − beam. The two MetalumyTM sheets with 25µm were pasted on the inner surface of the detector frame and the inserted reflection mirror. The aerogel
radiator was supported with cotton strings at the downstream side. In order to calibrate the PMT’s gain,
one optical fiber was inserted into the detector frame though a hole. The optical fiber was connected to
LED and could provide photons inside the detector.
• AC2 (diffused reflection)

30
The structure of AC2 is the almost same with AC1. In AC2, the reflection mirror is not mounted
because AC2 has a diffused reflector. The three sheets of Teflon with 80 µm thickness were pasted innersurface of the counter frame. Because AC2 has no additional structure such as the reflection mirror
in AC1, it is suitable to check the radiator’s thickness dependence on the photon yield. We originallyprepared the support cotton string’s holes corresponding to 15, 30, 45 and 60 mm, respectively, on theside frame. The optical fiber for the PMT’s calibration is also mounted to the frame.

TransmittanceTransmitance of Aerogel radiator
1
0.9
0.8
0.7
0.6
0.5

Normal type

0.4

Clear type

0.3
0.2
0.1
0
200

Fig.4. Photograph showing the insides ofthe detector frames of AC1 (right,
mirror reflection) and AC2 (left, diffused reflection)

300

400

500

600

700
800
Wavelength [mm]Fig.5. Transmittance of the aerogel radiator of n = 1.10. The black andred points represent the transmittances for the normal and hightransparency types, respectively.

Fig. 4 shows a photograph of the insides of the detector frames for AC1 and AC2.
3.2 Aerogel radiator of n = 1.10
In this prototype, we checked the effect of the transparence type. Fig. 5 shows the measured transmittance of the aerogel radiator with n = 1.10 for both normal and clear types. The typical transmission
lengths are 20 mm and 40 mm at the wavelength of 400 nm for the normal and clear types, respectively.
The advantage of the clear type is that much larger photon yield is expected to minimize the absorptionof the radiated photon in the aerogel radiator thanks to its longer transmission length. However, theextraction rate of the clear type is lower than that of the normal type due to the difficulties at the production process. Therefore, we decided to finalize the transparence type after checking performance forboth types in the beam experiment. The maximum available size of the aerogel radiator was 100 × 100

× 15 mm3 . For this prototype counter, we prepared two sets of radiator tile of 75 × 100 × 15 mm3 and75 × 85 × 15 mm3 . In order to minimize the ineffective area at the gap between two tiles, the tiles wereplaced with a staggered manner to the beam direction as shown in Fig. 6 in the next subsection.
3.3 Performance test experiment with a position beam

We performed a test experiment of this prototype detector using a positron beam in the GeV-γ test
beam line at ELPH in June 2016. The momentum of the positron beam was set to be 580 MeV/c. The
purpose of this experiment was to determine the optimal condition for AC counter by changing some

31

Fig.6. Detector setup in this test experiment. T1 and T2 are the beam defining counters. V1, V2,V3 and V4 are placed to veto the e+ e− shower event. AC1 and AC2 are the AC counterswith the mirror reflection and diffused reflection, respectively. The aerogel tiles are put
with a staggered manner.

parameters, such as reflection type, radiator transparent type and its thickness and so on. Then for the
optimal condition, we checked the position and beam direction dependences for the photon yield. The
beam rate dependence for the detection efficiency was also measured up to 150 kHz to check the detector
performance at the higher singles rate condition.
Fig. 6 show the experimental setup. In order to define the positron beam, we installed two plastic
scintillation counters (T1, T2) at the upstream and the downstream of the beam line. AC1 with themirror reflection and AC2 with the diffused reflection were installed between T1 and T2 counter. In
order to veto the e+ e− shower events, four plastic scintillation counters (V1, V2, V3 and V4) were placedat the downstream of AC2. V3 and V4 were placed apart from the beam center horizontally as shownin Fig. 6. V1 and V2 were placed vertically with the same manner. The experimental trigger was thecoincidence between T1 and T2. The four veto counters were used in the offline analysis to requestingno hit on these counters. The charge and time information were digitized with a QDC module (CAENCounts/p.e.

V792) and a TDC module (CAEN V775), respectively.

2000
1800
1600

AC1
Efficiency : (99.947+-0.009)[%]mode : (15.84+-0.48)[p.e.]

1400
1200
1000
800
600
400

Fig.7. Coordinate plane at each AC detector. The cross points show the beam
position at the study of the position
dependence. The red point is thereference point of this study.

200
0
0

10

20

30

40

50

60

70

80

90

100
Np.e.

Fig.8. Obtained photo-electron (p.e.) distribution for AC1 with a clear typeradiator of 30 cm thickness.

32
Fig. 7 shows the coordinate plane at each AC detector. The cross points show the beam positionat the study of the position dependence. The red cross point of (x, y) = (25, 0) is the reference point of
the study. For other studies such as the radiator thickness study, beam was irradiated to this reference
point. Fig. 8 shows the obtained photo-electron (p.e.) distribution for AC1 with a clear type radiator of 30
cm thickness. The p.e. number was derived by using the coefficient from ADC to p.e. which is evaluatedfrom the LED system. In the following analysis, we used the most probable value of p.e. distribution
and the efficiency as the criteria of the performance check. The efficiency was defined as
ef f iciency =

NAC
.
NBeam

(1)

NBeam was the number of event samples where T1 and T2 counters had correct timing in TDC spectraand four veto counters (V1, V2, V3 and V4) had no hit. NAC was the number of hit of AC where werequested the p.e. number should be larger than the software threshold of 3 p.e., because the hardware
threshold was rather low value of ∼0.5 p.e. and the accidental hit due to the dark current could betriggered.

30

(a)

Efficiency [%]Mode[p.e.]

3.3.1 Radiator thickness dependence

100

(b)

99.5

25

99
20
98.5
AC1 Clear
AC1 Normal

15

AC1 Clear
AC1 Normal

98

AC2 Clear
AC2 Normal

10
10

15

20

25

30

35

40
45
50
Thickness [mm]

AC2 Clear

97.5
97
10

AC2 Normal

15

20

25

30

35

40
45
50
Thickness [mm]Fig.9. Radiator thickness dependence for the p.e. yield (a) and efficiency (b). The blue and red
points show the results for AC1 (mirror reflection) and AC2 (diffused reflection), respectively. The square and triangle show the clear and normal transparency types, respectively.

At first, we checked the radiator thickness dependence for the most probable value of the p.e. number and the efficiency. The beam position was the reference position in Fig. 7 and the beam rate was 1.5
kHz. Fig. 9 (a) shows the radiator thickness dependence for the p.e. yield for all combinations of thetransparent type (Clear and Normal) and the reflection method (mirror reflection : AC1 and diffused reflection : AC2). When we compared the reflection method, larger p.e. yield was obtained for the diffusedreflection type (AC2). The p.e. yield increased with the radiator thickness but the p.e. number was not
linear with the thickness and saturated at the larger thickness due to absorption in the radiator. However, the clear type kept much better linearity with the thickness thanks to the better transmittance.
The most important point was that the sufficient p.e. yield more than 20 p.e. could be obtained even for

33
the normal transparent type with 30 mm thickness. Fig. 9 (b) shows the radiator thickness dependence
for the efficiency. By using the radiator thickness more than 30 mm, the efficiency of 99.9% was obtained for all combinations. From these results, we concluded that the aerogel radiator with the normaltransparent type was the best candidate considering the extraction rate at the production process.
3.3.2 Position dependence
Table 1. Summary of the basic operation conditions for AC1 and AC2.
Reflection type
Aerogel type
Aerogel thickness
PMT operation voltage
ADC value (Charge) for 1 p.e.
Discriminator threshold

AC1
Mirror reflection
Clear type
30 mm
1.8 kV74.8 ch (7.5 pC)
20 mV

AC2
Diffused reflection
Normal type
30 mm
1.8 kV38.4 ch (3.8 pC)
20 mV

From here, we studied the other dependencies such as the position dependence and so on. These
points depend not only the reflection method but also the transparency type of the radiator. However,
because there was no large difference between two transparency types when the thickness was 30 mm,
we installed the clear type radiator and the normal type radiator into the AC1’s frame (mirror reflection)and the AC2’s frame (diffused reflection), respectively. The basic operation conditions of two AC counters
are summarized in Table 1 .
The position dependences of the AC detectors were studied by changing the beam position to totally
15 points as shown by cross points in Fig. 7. Fig. 10 (a) shows the position dependencies of the mostprobable value of the p.e. yield for AC1 (blue points) and AC2 (red points). In AC2 with the diffusedreflection, the p.e. yield increased depending on the distance between PMT and beam position (photon
source point), that is, when the distance is short, the p.e. number is large. On the other hand, in
AC1 with the mirror reflection, the p.e. number reached the minimum at x = 100 mm, where was the
cross point between the tilted mirror and the downstream detector frame. In the mirror reflection, theunwanted position dependence could appear and this also caused the loss of the efficiency as shown in
Fig. 10 (b). The diffused reflection type was much better to obtain the uniformly high efficiency.
3.3.3 Angular dependence
In the E40 experiment, the charged particle enters the AC counter with some angles up to 30
degrees. The angular dependence was also studied. Fig. 11 shows the results on the angular dependence,
where the y position was fixed to be 0 and the x position was changed to 4 points from 25 mm to 100
mm. At each beam position, the detector was placed with the tilt angle from 0 degree to 30 degrees forthe beam direction. Because the pass length in the radiator increased with the angle, the Cherenkov
radiated photons also increased. In AC2, as expected, the obtained p.e. number increased with the angle
for all x positions. On the other hand, in AC1, the angular dependence was different at the x position

35

(a)
30

Efficinency[%]Mode[p.e.]

34

100

(b)

99.8
99.6

AC1 y=-22.5[mm]AC1 y=0 [mm]AC1 y=22.5 [mm]AC2 y=-22.5[mm]AC2 y=0 [mm]AC2 y=22.5 [mm]

25

20

99.4

AC1 y=-22.5[mm]AC1 y=0 [mm]AC1 y=22.5 [mm]AC2 y=-22.5[mm]AC2 y=0 [mm]AC2 y=22.5 [mm]

99.2
99
98.8
98.6

15

98.4
98.2

10
0

20

40

60

80

98
0

100 120 140 160 180
x position[mm]

20

40

60

80

100 120 140 160 180
x position[mm]

40

(a)
35

Efficiency [%]Mode[p.e.]

Fig.10. Position dependence for the p.e. yield (a) and efficiency (b). The blue and red points
show the results for AC1 (mirror reflection) and AC2 (diffused reflection), respectively.
The square, triangle and circle show the results at y=−22.5 mm, 0 mm and 22.5 mm,
respectively.

100

(b)

99.8
99.6

AC1

30

AC2
x=25 mmx=50 mmx=70 mmx=100 mm

25
20

AC1

99.4

AC2
x=25 mmx=50 mmx=70 mmx=100 mm

99.2
99
98.8
98.6
98.4

15

98.2
10

0

5

10

15

20

25

30
35
40
Angle [degree]

98

0

5

10

15

20

25

30
35
40
Angle [degree]

Fig.11. Angular dependence for the p.e. yield (a) and efficiency (b). The blue and red points
show the results for AC1 (mirror reflection) and AC2 (diffused reflection), respectively.
The square, triangle, circle and cross show the results at x=25 mm, 50 mm, 75 mm and100 mm, respectively.

due to the angular dependence of the photon collection ratio.
3.3.4 Beam rate dependence
In the E40 experiment, high singles rate of ∼300 kHz is expected for the AC counter. In this test

experiment, the beam rate dependence was also studied by increasing the beam intensity up to 150 kHz
which was the maximum beam intensity at this experiment. The beam position was the reference point
as shown by red cross point in Fig. 7. Fig. 12 shows the pulse hight ratio (a) and the efficiency (b) inthe standard operation condition where PMT’s HV was 1.8 kV for both AC1 and AC2. As can be seen in
Fig. 12 (a) where the ratio of the mean p.e. number for the reference value at 1.5 kHz beam intensity
is shown, the pulse height decreased with the increase of the beam intensity due to the increase of thedynode current at the last stage in PMT. Because the PMT in AC1 has a larger gain even for the same

35
operation voltage, the ratio dropped rapidly with the beam intensity. The efficiency also decreased withthe beam intensity and could not keep the 99% efficiency even for 80 kHz. In this PMT type, the potential
voltage for the final stage of the dynode can not be load from the outside. Therefore, in order to reduce
the load current in the dynode, we decreased the operation HV down to 1.3 kV. Fig. 13 (a) shows theratio of the mean p.e. number for each operation voltage at the beam intensity of 150 kHz. In order tocompare with the reference data at HV = 1.8 kV and beam intensity of 1.5 kHz, the mean p.e. number
was compared by measuring the ADC value for 1 p.e. for each operation voltage. From this study, theoriginal p.e. yield can be recovered by setting the lower operation voltage around 1.4 kV. The efficiency

100

Efficiency[%]

Drop ratio[ch/ch(1.5kHz)]

more than 98% could be kept at high single rate condition of 150 kHz by setting the lower HV value.

1
0.9

95
90

0.8
85
0.7
80

0.6

AC1

0.4

AC1
75

AC2

0.5

0

20

40

60

80

100

70
0

120 140 160
Beam rate[kHz]

AC2

20

40

60

80

100

120 140 160
Beam rate[kHz]

1.2

(a)

1.1
1

Efficiency[%]

drop ratio[p.e./p.e.(1.5 kHz)]

Fig.12. Beam rate dependence for the pulse height ratio (a) and efficiency (b) at the standard
operation condition in Table 1. The blue and red points show the results for AC1 (mirror
reflection) and AC2 (diffused reflection), respectively.

100

(b)

95
90

0.9
85

0.8

80

0.7

AC1

0.6

AC1
75

AC2

AC2

0.5
70
1.3

1.4

1.5

1.6

1.7

1.8
HV [kV]

1.3

1.4

1.5

1.6

1.7

1.8
HV [kV]

Fig.13. Operation HV dependence for the mean p.e. number’s ratio (a) and efficiency (b) at thebeam intensity of 150 kHz. The blue and red points show the results for AC1 (mirror
reflection) and AC2 (diffused reflection), respectively.

36
3.3.5 summary and discussion in the test experiment
From this test experiment, we could obtain three important results. The first result was that the
aerogel radiator of n = 1.10 emitted a large number of Cherenkov radiated photons and the sufficient p.e.
number of ∼20 could be obtained even for the normal transparence type. We decided to use the aerogel
radiator with the normal transparent type for the actual AC counter by considering the extraction rate

at the production process. The second result was that the diffused reflection was superior for all study
points, that is, the p.e. yield, the position dependence and the angular dependence. Finally, PMTs shouldbe operated at the low HV value to prevent from dropping the gain at the high dynode current condition.
In the lower HV operation, the pulse height becomes smaller. To compensate the lower gain in PMT, thePMT signal is again amplified with the electric circuit in the actual AC counter.
3.3.6 Optimization of the parameters in the Geant4 simulation
The optical simulation in Geant4 is the one of the most powerful tools to estimate the performanceof the optical detector such as the Cherenkov detector. However, there are some parameters to be determined to get a realistic simulation result. As shown in Fig. 2, we performed the Geant4 simulation
before the test experiment. In this simulation, there were many uncertainties in these parameters.
Here, we adjusted these parameters such as the absorption length in the aerogel radiator by comparing
the simulation result with the experimental result. It might be worth describing how to determine theseparameters to apply the simulation to other detectors.
• Parameters for PMT
The quantum efficiency of the photo cathode was measured by Hamamatsu Photonics and the values were used in the simulation.
The response function for 1 p.e. in the fine-mesh is not straight forward because some portionof the photo-electron does not hit the mesh-type dynode and move to next dynode stage without any
amplification. The response of the fine-mesh PMT was studied in the past research [4] and we also
followed the simulation method. Fig. 14 shows the flow chart of this simulation. The probability thatthe photo-electron does not hit the single dynode mesh is obtained to be 40% from the reference [4].
When the photo-electron does not hit the dynode, the gain is one. On the other hand, when the photoelectron hits the dynode, it could be absorbed in the dynode with some probabilities depending on the hit
position on the dynode mesh. If the photo-electron hit near the center of the wire of the mesh, it could
be easily absorbed. This absorption probability was set to be 10% from the reference. When the photoelectron is not absorbed, the amplification factor is obeyed by the Poisson distribution with the meanvalue of M which should be determined by minimizing the difference between the simulation result
and the experimental result. The number of the dynode stage of the PMT was 19 and the simulation
should be performed for all 19 dynode stages. However, it is already studied from the reference that areasonable simulation result can be obtained by continuing for 6 dynode stages. In our simulation, we
also performed for 6 dynode stages. Fig. 15 shows the QDC spectrum for small photon input from LED
and reproduced simulation result. The amplification factor M was obtained to be 3.5 by minimizing the37
reduced χ2 value between these two histograms. The simulated spectrum could be reproduced well withCounts/ch

the minimum reduced χ2 of 2.

Start amplification
for single electron

Yes (60%)

Hit position was centerof dynode wire ?

Yes (10%)Multiplied with Poisson distribution
with mean value of M
Multiplication factor : P(M)

102

10

No (90%)
Pass through the dynodewithout amplification
Multiplication factor : 1

Experiment data
MC simulation
Pedestal, 1 p.e., 2 p.e., 3 p.e.

104
103

Hit dynode or not ?

No (40%)105

Absorbed in dynode wire
Multiplication factor : 0

Fig.14. Flow chart in the simulation to estimate the response function for 1
p.e. in the fine-mesh PMT.

1
100

150

200

250

300

350

400

450
500
QDC [ch]Fig.15. Comparison between the QCD
spectrum for small photon input
from LED and reproduced simulation result.

• Parameters for the aerogel radiator

The parameters related to the aerogel radiator are refractive index, scattering length and absorp-

tion length.
The refractive index, in general, has a wavelength dependence as studied in other references [5] [6].
In our study, we used one pole model to take into account the wavelength dependence. In this model,
the refractive index n(λ), where λ is the wavelength of incident photon, is represented by the following
equation,n(λ)2 − 1 =a0 λ2.
λ2 − λ20(2)

The parameter a0 is the coefficient proportional to the density and λ0 is a constant value and is set
to 90 nm from the reference. In our aerogel radiator, the refractive index was measured to be 1.10 fora wavelength of 405 nm. Therefore the a0 value can be obtained. In our simulation, this wavelength
dependence was taken into account for the refractive index.
The scattering length (Lscat ) can be calculated from the measured transmittance (T ) with the following equation,
Lscat = −

t
,
ln T

(3)

where t is the thickness of the radiator when transmittance T is measured. Strictly speaking, the transmittance is determined by both two effects of scattering and absorption. However, in case of aerogel, theabsorption length is much longer than the scattering length and its effect for transmittance is negligibly
small. Fig. 16 shows the measured scattering length for our aerogel radiator. We used this informationin the simulation.
The absorption length is the most difficult parameter to estimate. We also estimated the absorption
length from the test results. In this simulation, we assumed that the absorption length has the same

Lscatt[cm]

38

20
18
16

n=1.10 NormalType14

n=1.10 ClearType

12
10
8
6
4
2
0
250

300

350

400

450

500

550
600
650
Wavelength[nm]Fig.16. Measured scattering lengths of our aerogel radiators for the normal type (red) and theclear type (blue).

wavelength dependence with the scattering length and the absorption length Labs (λ) is represented by
the following relation,
Labs (λ) = Abs × Lscat (λ).

(4)

The coefficient Abs should be derived with inductive approach by reproducing the p.e. distribution datawith the simulation result. As will be mentioned later, the Abs value was obtained to be 102.5 bysearching for the minimum reduced χ2 value between the experimental data and the simulation.
• Comparison with the experimental data and the simulation
By taking into all points discussed above, the Geant4 simulation for the prototype detectors was
performed again. Fig. 17 shows the comparison between the experimental data of AC2, where theaerogel radiator was the normal type with 30 cm thickness and the reflection type was the diffusedreflection, and its simulation result. In order to check the reproducibility for other conditions, the dataof radiator thickness study were also compared with the simulations as shown in Fig. 18
The simulation could reproduce data rather well, though there was still room to be improved. However, reproducibility with this level is quite satisfactory because this simulation enables us to estimate
the p.e. yield with more than 10% precision.

§ 4. Performance test of the AC actual detector
4.1 Fabrication of the AC counter

Based on the result of the test experiment, we finalized the design of the AC actual detector andstarted fabrication of the AC counter. The outer size of the detector was already determined from thespatial limitation as shown in Fig. 2. Fig. 19 shows the photos at the fabrication process. The counter
was divided into four rooms by 0.3 mm thickness Al plates and the 3 sheets of Teflon with 80 µm thickness were pasted on the inner surface of the each room. The normal transparence type aerogel radiatorwith refractive index n = 1.10 was used. Two tiles of the aerogel radiator of 15 mm thickness were

2200

(a)

25

1800

20

1600

15

1400

10

1200

5

1000

0

Mode[p.e.]

2000

2/Ndf

Counts/p.e.

39

(b)

28
26
24
22

70

80

90

100 110 120 130Abs

20

800
MC simulation
Experiment data

600
400

18

MC Clear type16

MC Normal type
Exp Clear type

14

200
0
0

30

10

20

30

40

50

60

70

80

90

100

Np.e.

Fig.17. (a) Comparison between the experimental data (blue) of AC2
where the aerogel radiator was
the normal type with 30 cm thickness and the reflection type was
the diffused reflection, and its
simulation result (red). (b) Estimation of the best Abs value
by searching for the minimum reduced χ2 value.

Exp Normal type

12
10
10

15

20

25

30

35

40
45
50
Thickness [mm]Fig.18. Comparison between data (red)and simulation (blue) for different radiation thicknesses. The
square and triangle represent results for the clear and normal
types, respectively. The estimatedp.e. yield was consistent with data
within 10% precision.

mounted and one tile was put on the other tile with the staggered manner in order to reduce ineffective
region caused by the gap between the neighbor plate. The aerogel radiators were supported by the cotton strings as shown by red arrows in Fig. 19 which were attached to the detector frame through thehole. Some of the cotton strings were exchanged to the optical fiber for the calibration by guiding lightsfrom LED. The fibers had some cracks on the surface and the light in the fiber can easily escape fromthe optical trap in the fiber to provide photons to PMTs. Totally 12 PMTs were mounted upside anddownside of the detector.
Fig. 20 shows the expected p.e. yield for the AC counter from the Geant4 simulation which was
tuned with the test experiment. In all rooms, the sufficient p.e. number of ∼20 is expected. In actual

operation, it is the most important that this performance should be kept at the high singles rate condition. To check these points, we again performed a test experiment at the same beam line in ELPH in
November 2016.
4.2 Performance test experiment with a positron beam (2)We performed a test experiment for the AC actual detector using a position beam in the GeV-γ test
beam line at ELPH for three days in November 2016. The purpose of the experiment is to evaluate
the performance of the AC counter at high single rate condition in addition to check the general study
topics such as position dependence. By changing the operation condition such as the single p.e. gain of
PMTs and the threshold of the discriminator, the operation condition was optimized. The experimental
setup was almost the same with the previous experiment in Fig. 6. The prototype detectors (AC1, 2) were
replaced by the AC actual counter. Fig. 21 shows the beam points to check the position dependence where40

Mode : 19.30+-0.11 [p.e.]

0.06

0.04

0.03

0.03

0.02

0.02

0.01

0.01
10

20

30

40

50

0.06

60

70

80

0
0

100
Np.e.

(c)

Room3

0.05

90

Mode : 18.06+-0.07 [p.e.]

(b)

Room2

0.05

0.04

0
0

Counts/p.e.

(a)

Room1

0.05

Counts/p.e.

0.06

Counts/p.e.

Counts/p.e.

Fig.19. Photographs at the fabrication process of the actual AC detector. The cotton strings
shown as red arrows is used to support the aerogel radiators. The blue arrows show the
optical fiber for the calibration by guiding lights from LED.

Mode : 19.33+-0.07 [p.e.]

10

20

30

40

50

60

70

80

0.06

100
Np.e.

(d)

Room4

0.05

90

Mode : 21.79+-0.11 [p.e.]
0.04

0.04
0.03

0.03

0.02

0.02

0.01

0.01
0
0

10

20

30

40

50

60

70

80

90

100

Np.e.

0
0

10

20

30

40

50

60

70

80

90

100
Np.e.

Fig.20. The expected p.e. yield for the AC counter from the Geant4 simulation which was tuned
with the test experimental data.

the red cross points show the reference positions for each room. In this experiment, the mean beam rate
was increased up to ∼600 kHz. However the extracted beam in one spill had the time dependence asshown in Fig. 22 where the logic signal from PMT1U was input to the universal FPGA module (HULmodule) and the instantaneous beam rate for every triggered timing was calculated from the increasesof the counters of the logic signal and clocks for time measurement between the two triggered events. In
the analysis, the instantaneous beam rate was taken into account.

Rate[kHz]

41

1600
1400
1200
1000
800
600
400
200
0
0

Fig.21. Beam position at the test experiment to check the position dependence. The red cross points show
the reference positions for each
room.

2

4

6

8

10

12

14

16
18
Time[ms]

Fig.22. Instantaneous beam rate in one
spill.

4.2.1 The photo-electron yieldFig. 23 shows the typical p.e. yield for the room4 segment. The left 8 histograms show the p.e. yieldfor each PMT and the p.e. yields were added in software and the right figure was obtained. The obtained

PMT 5U

6000

7000

PMT 6U

6000

5000

4000

Counts/p.e.

PMT 4U

5000

Counts/p.e.

PMT 3U

4000

Counts/p.e.

5000

Counts/p.e.

Counts/p.e.

p.e. yield was almost consistent with the simulation shown in Fig. 20.

5000
4000

3000

4000

3000
3000
2000

2000

3000

2000

2000

1000

1000

1000

1000

0
0

0
0

0
0

0
0

10 15 20 25 30 35 40 45 50
Np.e.

10 15 20 25 30 35 40 45 50
Np.e.

6000

PMT 4D5000

PMT 5D

5000

4000
3000

5

2000

1000

1000

1000

5

10 15 20 25 30 35 40 45 50
Np.e.

0
0

400
200

3000

5

10 15 20 25 30 35 40 45 50
Np.e.

0
0

0
0

1000
5

10 15 20 25 30 35 40 45 50
Np.e.

Mode: 23.59+-1.77[p.e.]

1000

600

2000

0
0

1400

800

4000

3000

2000

10 15 20 25 30 35 40 45 50
Np.e.

6000
5000

3000

Software Sum

PMT 6D

7000

4000

2000

(b)

1600

1200
5

Counts/p.e.

PMT 3D

4000

5Counts/p.e.

5000

10 15 20 25 30 35 40 45 50
Np.e.

Counts/p.e.

Counts/p.e.

5

1800

0
0

5

10

20

30

40

50

60

70

80

90

100
Np.e.

10 15 20 25 30 35 40 45 50
Np.e.

Fig.23. Typical p.e. yield for the room4 segment. The left 8 histograms show the p.e. yield foreach PMT and the right histogram shows these summation.

4.2.2 The high rate study
We checked the performance at the high singles rate condition. As shown in Fig. 22, there was atime dependence in its instantaneous beam rate. In the analysis, each triggered event was categorized
into three instantaneous beam rates of ”100 kHz” from 0 to 200 kHz, ”300 kHz” from 200 to 400 kHz
and ”600 kHz” from 400 to 800 kHz. As for the PMT gain, we prepared three different operation points
corresponding to 20, 40 and 60 QDC channels for single p.e. pulse charge. Here, the PMT signals areconnected to the amplifier with 10 times gain to operate in the lower operation voltage. Therefore the42present gain was different from that at the previous test experiment for the prototype detector. The
beam positions were set to the reference position as shown by the red cross point in Fig. 21. Fig. 24
shows the beam rate dependence of the pulse height for each single p.e. gain. The most probable valueof the p.e. distribution at each beam rate was normalized with that at 100 kHz beam rate. Due to the
AC coupling of the PMT output, the baseline of the signal shifted upside with the increase of the beam
intensity. In Fig. 24 the effect of the pedestal shift was corrected. In the gain of 20, no gain drop was
found. On the other hand, in the gain of 40 and 60, the gain was reduced down to 90%. However, thegain drop of this level was acceptable. Fig. 25 and 26 shows the efficiencies for each room at the mean
beam rates of 300 kHz and 600 kHz, respectively. Here, the horizontal axis shows the discriminator
threshold applied in the hard level and the hard level threshold was converted to p.e. value in software.
The room4 kept the most high efficiency because the p.e. yield was the largest. In the mean rate of 300
kHz, which is the expected singles rate in E40, the efficiencies more than 98% could be obtained for all
room segments by setting the threshold less than 6 p.e. value. At 600 kHz, the efficiencies became lower

gain drop[ch/ch(100 kHz)]a little bit. Even in this rate, by setting threshold around 4 p.e., 97% efficiency could be obtained.
1.1

1.05
1

0.95
0.9
gain 20 ch/p.e.
gain 40 ch/p.e.

0.85
0.8

gain 60 ch/p.e.

100

200

300

400

500

600
rate[kHz]

Fig.24. Beam rate dependence of the pulse height for three p.e. gains. The red, green blue points
show 20, 40 and 60 p.e., respectively. The error mainly comes from the uncertainty ofthe baseline shift.

4.2.3 The position dependence
Next, the position dependence of the performance was evaluated. The studied points were shownin Fig. 21 and the beam rate was set to about 30 kHz. The PMT gain was 40 ch for single p.e. charge.
Fig. 27 (a) shows the most probable value of the p.e. distribution for each point. As expected from theprototype detector, the p.e. yield increased when the beam position became near the PMTs. Fig. 27 (b)shows the efficiencies and the efficiencies more than 99% were obtained for all positions in this beam
rate.
Finally we check the effect that the charged particles passed through the neighbor rooms such as
room1 and room3. In case of room1 and room3, the beam position was set at the partition of the Al plate
and the detector was placed with a tilt angle of three degrees, which corresponded the angle from the

100

(a)

98
96
94

Efficinency[%]

Efficinency[%]

43

(b)

98
96
94

Room1
Room3

92

100

Room1
Room3

92

Room4

Room4

90

90

Efficinency[%]

2

4

6

8

10
12
Threshold[p.e.]

2

4

6

8

10
12
Threshold[p.e.]

100

(c)

98
96
94

Room1
Room3

92

Room4

90
2

4

6

8

10
12
Threshold[p.e.]

100

(a)

98
96
94

Efficinency[%]

Efficinency[%]Fig.25. Efficiencies for each room at the mean beam rate of 300 kHz for p.e. gains of 20 (a) , 40(b) and 60 (c).

100

(b)

98
96
94

Room1
92
90

Efficinency[%]

88

Room1
92

Room3

2

4

Room3

90

Room4
6

8

10
12
Threshold[p.e.]

88

Room4
2

4

6

8

10
12
Threshold[p.e.]

100

(c)

98
96
94

Room1
92

Room3

90
88

Room4
2

4

6

8

10
12
Threshold[p.e.]Fig.26. Efficiencies for each room at the mean beam rate of 600 kHz for p.e. gains of 20 (a) , 40(b) and 60 (c).

target position in the E40 setup. In case of room3 and room4, the tilt angle was set to be 8 degrees.
Fig. 28 shows the summed p.e. distribution for neighbor rooms. In these positions, the p.e. yielddecreased especially at the partition of room1 and room3. Due to the aluminum partition, the net passlength in the aerogel radiator decreased and the p.e. yield also reduced. At the partition of room3 androom4, because the particle had the larger tilt angle, the effect of this partition reduced and the muchbetter p.e. distribution could be optained. In order to measure the efficiency, the signals were linearly
added by using the Linear FIFO and the output signal was discriminated. Fig. 29 shows the threshold

35

Room1 x=0[mm]Room4 x=170[mm]Room2 x=0[mm]Room4 x=280[mm]Room3 x=79.5[mm]Room4 x=390[mm]

30

100.2

Efficinency[%]Mode[p.e.]

44

Room1 x=0[mm]Room4 x=170[mm]100.1

Room2 x=0[mm]Room4 x=280[mm]100

Room3 x=79.5[mm]Room4 x=390[mm]

99.9
99.8

25

99.7
99.6

20

99.5
99.4

15
-200 -150 -100

99.3
-50

0

50

100 150 200
y position[mm]99.2-200 -150 -100

-50

0

50

100 150 200
y position[mm]Fig.27. Position dependence for the p.e. yield (a) and efficiency (b) at the beam rate of 30 kHz.

dependence of the efficiency at these partition positions. As a reference, the efficiencies at the normal
position for each room were also overwritten. At the partition of room3 and room4, rather high efficiencyof 97% could be obtained. On the other hand, the partition position at room1 and room3 resulted inlower efficiency around 93%. However, when we performed the simulation taking into account this effectfor the E40 detector configuration where the charged particles were generated from the target with therealistic incident angle, the total efficiency was obtained to be 98%. Therefore this partition effect was
not a serious problem.

Fig.28. Summed p.e. distribution for neighbor rooms when the beam passes through the partition area. The beam positions were at the border between room1 and room3 (a) and at
the border between room3 and room4 (b).

4.2.4 Summary of the test experiment
The AC counter using a normal transparence type aerogel radiator with the refractive index of 1.10
was studied by using a positron beam. We adopted the defused reflection method with a Teflon sheet.
As expected from the simulation, the AC counter showed the enough performance such as the p.e. yieldand position dependence. The most probable p.e. numbers were larger than 15 p.e. for all positions andthe efficiencies were more than 99% at the beam rate of 30 kHz. At the higher beam rate up to 600 kHz,
there were still gain drop in the PMTs. However, the gain drop was well suppressed by operating theEfficinency[%]

45

100
99
98
97
96

3,4 partition
1,3 partition
Room1
Room3
Room4

95
94
93
92
1

2

3

4

5

6

7

8
9
10
Threshold[p.e.]Fig.29. Threshold dependence of the efficiency at the border positions. The efficiencies at thenormal position for each room were also overwritten as a reference.

PMTs at lower HV value and by keeping the pulse height with the additional electrical amplifier. The
efficiency was obtained to be more than 97% at the high rate condition. The AC counter had internal
four rooms which were separated by the aluminum partition to reduce the singles rate for each PMT.
Because the partition made an ineffective area, the efficiency decreased to 93% when the particle passed
through around the partition region. However, the effect was negligible at the E40 experimental setup.
We concluded that the AC counter satisfied the requirements to keep more than 97% efficiency at theactual single rate condition.

§ 5. Summary

We developed an Aerogel Cherenkov Counter (AC) with the index of 1.10 for the Σp scatteringexperiment at J-PARC which was used to veto π particles of momentum range up to 1.4 GeV/c. The
size of AC was 480 (H) × 400 (V) × 80 (T) mm3 which was determined from a geometrical conditionof a magnetic spectrometer (KURAMA spectrometer). In order to obtain detection efficiency more than
97%, we adopted the aerogel radiator with index of 1.10 which was rather high index as an aerogeland totally 12 fine-mesh PMTs were used to collect enough photons. The other requirement was that
this AC should keep the efficiency under the high single rate condition up to 300 kHz which was the
expected value in the Σp scattering experiment. We asked Chiba university group to make the aerogel
radiators of n = 1.10. They accumulated a skill to make a very transparent type of the aerogel radiator.
At first we fabricated the prototype detectors to compare the transparent type of the aerogels and thereflection method, that is, the mirror reflection or the diffused reflection. From the test experiment using
a positron beam, as for the reflection method, the diffused reflection was superior at the all study points.
As for the transparency, the clear type showed the larger p.e. yield especially when the thickness of
the radiator increased. However, the normal type also showed the sufficient p.e. yield of 20 with 30
mm thickness. Therefore we selected to use the normal type radiator considering the difficulty at the
production process of the clear type.

46
One of the important points in this work is that the realistic optical simulation using Geant4 wasconstructed. One of the most uncertain parameters in the simulation was the absorption length in the
aerogel radiator. By minimizing the difference between the simulation and the experimental p.e. yield,
the absorption length can be estimated to be the 100 times longer value than the scattering length thatcan be measured. By using this value, the optical simulation could reproduce the experimental results
such as the radiator’s thickness dependence for the p.e. yield within a 10% accuracy.
The AC actual counter using the normal transparence type aerogel radiator with the refractive
index of 1.10 was fabricated and its performance was evaluated again using the positron beam at ELPH.
We adopted the defused reflection method with a Teflon sheet. As expected from the simulation, theAC counter showed the enough performance such as the p.e. yield and position dependence. The mostprobable p.e. numbers were larger than 15 p.e. for all positions and the efficiencies were more than 99%
at the beam rate of 30 kHz. At the higher beam rate up to 600 kHz, there were still gain drop in the
PMTs. However, the gain drop was well suppressed by operating the PMTs at lower HV value and bykeeping the pulse height with the additional electrical amplifier. The efficiency was obtained to be morethan 97% at the high rate condition. We concluded that the AC counter satisfied the requirements tokeep more than 97% efficiency at the actual single rate condition.

Acknowledgment
We would like to express our thanks to the staffs of ELPH for their support to provide beam with theexcellent condition during the beam time. This work was supported by JSPS KAKENHI Grant Number
23684011 and 15H05442.

References[1]

M. Tabata et al.: Nucl. Instr. Meth. A668 (2012) 64.

[2]

M. Tabata et al.: Nucl. Instr. Meth. A795 (2015) 206.

[3]

K. Tanabe : Master’s thesis, Tohoku university (2015).

[4]

R. Enomoto et al.: Nucl. Instr. Meth. A332 (1993) 129.

[5]

M.F. Villoro et al.: Nucl. Instr. Meth. A480 (1993) 456.

[6]

T. Bellunato et al.: Eur. Phys. J. C 52 (2007) 759.

ELPH Annual Report, Tohoku University (2017)47(ELPH Experiment : #2868)

Performance Evaluation of Silicon-Tungsten
Electromagnetic Calorimeter Detector (ALICE FoCal) andHigh Timing Resolution MRPC-TOF for High Energy
Heavy Ion Experiment
R. Aoyama7 , T. Chujo7 , T. Hachiya4,5,6 , M. Hatakeyama7 , Y. Hoshi7 ,T. Ichisawa7 , M. Inaba8 , H. Kato7 , Y. Kawamura7 , D. Kawana7 , Y. Miake7 ,T. Nonaka7 , K. Ozawa3 , S. Sakai7 , H. Sako2 , T. Sakamoto4 , M. Shimomura4 ,T. Sugitate1 , T. Suzuki7 , K. Tadokoro7 , M. Takamura7 , and S. Takasu1
1
2

Hiroshima University, Kagamiyama, Higashi-Hiroshima 739-8526, Japan

Advanced Science Research Center, Japan Atomic Energy Agency, 2-4 Shirakata Shirane,
Tokai-mura, Naka-gun, Ibaraki-ken 319

3

KEK, High Energy Accelerator Research Organization, Tsukuba, Ibaraki 305-0801, Japan
4
5

6

Nara Women’s University, Kita-uoya Nishi-machi Nara 630-8506, JapanRIKEN Nishina Center for Accelerator-Based Science, Wako, Saitama 351-0198, JapanRIKEN BNL Research Center, Brookhaven National Laboratory, Upton, New York 11973-5000,
USA
7
8

University of Tsukuba, Tsukuba, Ibaraki, 305-8571, Japan

Tsukuba University of Technology, Tsukuba, 305-8520, Japan

In the ALICE experiment at the Large Hadron Collider (LHC) at CERN, there is an upgrade plan
to construct a Forward Calorimeter (FoCal) intended for the measurement of direct photons at forward
rapidity (3.5 < η < 5.3). In 2017, we made a new prototype of the electromagnetic part of FoCal detector,
including the new silicon sensors and new design of the flexible readout board to fix the design of miniFoCal detector, which is planed to produced and tested in 2018. We conducted the test beam experimentby using positron beams at Research Center for Electron Photon Science (ELPH). We measured thesignal of minimum ionizing particles (MIP) in this new prototype, and observed the gain variation for
MIPs depending on the position of silicon sensor. At the same time, we also conducted the beam test forthe prototype of Multi-gap Resistive Plate Chamber (MRPC) as a time-of-flight detector. This R&D of
MRPC is aiming for a good timing resolution better than 80 ps for the future use of J-PARC experiments.
At this time, based on the Electromagnetic field simulation, we developed a new prototype, in which therigid ground is in placed with the modification of readout pad shape. It is optimized for the impedance
matching and transmittance for the wide band signal including more than 1 G Hz frequency. We report
improvements of the new prototype.

48§ 1. Forward Calorimeter
1.1 Intruduction

In the LHC-ALICE, there is an upgrade plan to construct a Forward Calorimeter (FoCal). The
full FoCal detector installation during the long shutdown 3 (LS3) in 2024 is under the discussion. The
FoCal consists of an electromagnetic calorimeter (FoCal-E) and a hadron calorimeter(FoCal-H). FoCal-E
consists of low granularity layer (LGL) for the measurement of the photon energy, and high granularity
layer (HGL) for the identification of decay photons and direct-gammas. FoCal-E is a sampling-type
calorimeter using tungsten as the particle absorption layer and silicon as the detector layer. The silicon
used for LGL of FoCal-E is composed of 64 PADs of about 1cm × 1cm with the segmentation of 8 × 8. On

the surface of silicon, a flexible substrate with circuit for readout is attached, and the tungsten layer is
attached on the back side. The silicon PAD sensor we used in this test beam is shown in Fig. 1.
We use APV25 hybrid board (Fig. 2), Scalable Readout System (SRS) and mmDAQ for the readout.
APV25 is an analog pipeline ASIC developed for readout of silicon strip detector for the CMS experiment.
SRS refers to a system that collects the data from ADC boards and then converts the analog data fromAPV 25 to the digital (12 bits). The FEC board for SRS system processes data and slow control via DAQ
PC. The DAQ software called “ mmDAQ” is used in this test beam. Since 2014, we have been working
on the LGL detector, and at this time, we used the new silicon photo diode from HAMAMATSU (500µm thickness), and a new flexible print circuit board with wire bonding. No analog signal summing for
multiple silicon layers is used.

Fig.1. Silicon PADs with flexible board.

1.2 Setup
We placed the silicon sensor for FoCal in the dark box for the light shield. The inside of the darkbox is shown in Fig. 3. In this box, there are a detector, a remotely controllable moving stage, a scintillation counter for trigger. To define the beam spot, we use two 10cm × 10cm scintillation counters

and a 4mm × 4mm scintillation counter. These three counter’s coincidence signals were used as beam

49

Fig.2. APV25 hybrid board (CERN RD51).

triggers. And the detector is fixed on the stage, and it can be moved in horizontally and vertically withrespect to the beam axis. This moving stage is used for the position scan measurements. Also for themeasurements of an electromagnetic shower, we placed several tungsten plates in front of the detector.
1.3 Analysis
1.3.1 Observation of Electromagnetic Shower
To enhance the shower signals, the tungsten plates were placed in front of the detector. The purposeof this experiment is the measurement of MIP signals for all silicon pad sensor, so that the whole areaof the detector should be exposed by electromagnetic showers. In this measurements, we successfully
observed MIP signals and separated from the noise signal as shown in Fig. 4. The most right peak is
about twice as much compared to the middle peak, so that it indicates the signals of 2 MIP signals. Thischarge distribution is made by accumulating the singles for all PADs. The right panel shown in Fig.4 isthe simulation result by Geant4. The data agrees well with the simulation.
1.3.2 MIP Signal on All 8 × 8 Channels

One of the objectives of this beam test is to detect MIP signal in all silicon PADs and establish thegain calibration method for the individual pad. Fig. 5 shows the ADC value of MIP measured at each
PAD. There is one dead channel out of 64 PADs, but for other 63 PADs, ADC value of 1 MIP can be50

Fig.3. Setup in the dark box for FoCal.

Fig.4. Electromagnetic shower on data (left) and simulation (right) for the single silicon sensors.
The horizontal axis is the ADC value and the vertical axis is the number of counts.

clearly seen. As shown in Fig. 5, there is a trend that the ADC value is higher in the vicinity of thecenter and it gets lower as going outward.
One possibility of the ADC gain variation depending on the silicon location is the silicon wafer,because of the nearly round shape and low gain on the edge, and high gain around the center. It is
important to consider this gain variation in the calibration step, for the energy measurement of photons
as a calorimeter. We are planing to use the high intensity laser system to inject the infrared laser tosilicon, and calibrate the gain for pad by pad. Further detail of this measurements are summarized in
[2].

51

Fig.5. Position dependence of the MIP signal strength for all PAD sensors. The each square
represents the geometrical position of silicon sensor used in this test.

§ 2. Multi-gap Resistive Plate Chamber

Multi-gap Resistive Plate Chamber (MRPC) is a Time of Flight(TOF) detector. MRPC is a gas

chamber, and the signal is formed by the electron avalanche in the gas. Among many kinds of TOF
detector, MRPC is attractive because it can achieve good timing resolution at low cost which would
allow to make a large area TOF. For this reason, the MRPC technology is proposed to use the future
experiments at J-PARC.
2.1 Modification based on Electromagnetic field simulation
The electromagnetic field simulation is a useful tool to optimize the detector design and obtain abetter timing resolution. For this MRPC prototype, the simulation has done by Sony Global Manufacturing & Operations Corporation. The rigid ground is needed for the simulation, but usual MRPC does nothave such a ground in its structure as shown in Fig. 6. We first installed a rigid ground to MRPC andmodified some structure based on electromagnetic simulation. Fig .7 shows the new structure MRPC
tested at the experiment at ELPH.
High Energy
Charged Particle
Insulator

Resistive
PlatesReadout Pad

Electron Avalanche

CarbonGas
Gaps

Fig.6. Structure of conventional MRPCs.

This new type MRPC is expected to achieve the following goals.
• Cu ground surrounding the chamber to reduce the noise coming from outside.

High
Voltage52

CarbonSpacer260m

SMA connector

Inner
glass

Outer glass
Read outpad

Cu GNDFig.7. Structure of new type MRPC.

• Better impedance matching at readout pad, and better S/N.
• Enable to use the single-end preamplifier for readout.

We expect a better performance, especially in noise tolerance and property for the high frequency
signals by installing rigid ground and by use of the single-end readout.
2.2 Experiment and Analysis
2.2.1 Setup

Fig.8. Data taking diagram

The detail of the analysis is described in [3]. Fig. 8 shows the diagram for data taking. We usedcoincidence of PMT signals from No.1 to No.6 for start timing and beam trigger. MRPC generates stop
timing. The distribution of stop timing means the timing resolution of our MRPC. MRPC is placed in thegas box filled with R-134a and SF6 . The gas volume ratio is R-134a : SF6 = 100 : 5 and SF6 is a quencher
gas. We have two PMTs for each scintillation counter as shown in Fig. 9.
2.2.2 Data analysis and results
The signal shape and parameter definition is as described in Fig. 10. Data points are fitted by Sigmoid function defined as Eq. 1, and extracted the parameters as shown below. In this test, we succeeded
to read signals by the single end signal readout. Fig. 11 shows the TOF distribution of this new MRPC
prototype. We achieved 213.9 ± 6.6 ps timing resolution. This is better than the value from the previous

study by about 50 ps [1]. It leads to a simple readout design, and has a potential to improve the tim-

53

Charged Particle
Scinti&PMT

Gas box
MRPC

Read out
Pad

Scinti&PMT
Scinti&PMT

Fig.9. Setup around gas box

ing resolution by reading out the signal for high frequency band width, adopting the GHz preamplifier,[mV]which is available in the market.

Data
Sigmoid fitting

20
15
10
5
0
−5
−10
−15
60

62

64

66

68

70
[ns]

Fig.10. Signal shape and parameter definition. Horizontal axis is the time, and the vertical axis
is the pulse hight.

f (t) = a +d()
1 + exp b−tc

1. A : amplitude of signal.

(1)

54
2. P : pedestal, an integral of post peak.
3. T0 : stop timing. T0 is defined as timing the signal reaches half of its amplitude.
4. Trise : time length the signal takes to rise 10% to 90% of its amplitude.

Entries

TOF (corr.)
TOF (corr.)
140

EntriesMean
Std Dev

Data1107− 22.440.2989Gaussian fitting

120
100
80
60
40
20
0
−25

−24.5

−24

−23.5

−23

−22.5

−22

−21.5

−21

−20.5 −20
TOF [ns]

Fig.11. TOF distribution of new type MRPC

Acknowledgment
We would like to thank all its scientists, engineers and technicians at ELPH for their strong support
for our experiment, and ELPH accelerator teams for the outstanding performance of the GeV gamma
facility. This work was supported by JSPS KAKENHI Grant Numbers JP17H01122, JP15K13475, andJP26220707.

References[1]

T. Ichisawa, ”Multi-gap Resistive Plate Chamber R&D for the large area TOF for the future JPARC experiment”, (Bachelor thesis in FY 2016, Univ. of Tsukuba, Physics, in Japanese)[2]

K. Tadokoro, ”Performance evaluation of Front End Electronics with APV25 hybrid for LHCALICE FoCal”, (Bachelor thesis in FY 2017, Univ. of Tsukuba, Physics, in Japanese)[3]

M. Takamura, ”R&D of Multi-gap Resistive Plate Chamber (MRPC) detector; readout pad shapefor the high frequency signal readout and S/N improvement”, (Bachelor thesis in FY 2017, Univ.
of Tsukuba, Physics, in Japanese)

ELPH Annual Report, Tohoku University (2017)55(ELPH Experiment : #2870)

Development of high-rate detectors by using MPPC for the
charmed baryon spectroscopy experiment at J-PARC
K. Shirotori1 , T. Akaishi2 , H. Asano3 , R. Honda4 , T. Ishikawa5 , Y. Ma3 ,H. Noumi1 , A. Sakaguchi2 , H. Sako6 , T. N. Takahashi1 ,and for the J-PARC E50 collaboration
1

Research Center for Nuclear Physics (RCNP), 10-1 Mihogaoka, Ibaraki, Osaka, 567-0047, Japan2

Department of Physics, Osaka University, Toyonaka 560-0043, Japan
3

4
5

RIKEN, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan

Department of Physics, Tohoku University, Sendai 980-8578, Japan

Research Center for Electron Photon Science (ELPH), Tohoku University, Sendai, 982-0826,
Japan
6

Advanced Science Research Center (ASRC), Japan Atomic Energy Agency (JAEA), Tokai,
Ibaraki 319-1195, Japan

Fine segmented detectors for the high-rate beam measurement by using MPPC(Multi-Pixel Photon
Counter) are being developed for the charmed baryon spectroscopy experiment at J-PARC. For confirming the performances of the detector elements with MPPC, test measurements of the timing counter
with a plastic scintillator and an acrylic Čerenkov radiator, and the scintillation fiber counter were performed. We performed two experiments, for the first test of detector elements in November 2016 andthe high-rate beam test in October 2017. In the first test experiment, by using the combination of theplastic scintillator of 3 mm × 3 mm × 150 mm and 3-mm squared which is installed on the fast signal
shaping amplifier, the time resolution of ∼70 ps(rms) by the means of the Time-Of-Flight measurement

was obtained. The counters with the φ1.0-mm and φ0.5-mm scintillation fiber of 500-mm and 300-mm

length had a time resolution of ∼650 ps(FWHM) and ∼1050 ps(FWHM), respectively. In the high-rate

beam test experiment, we evaluated performances of the plastic scintillation and Čerenkov timing counters. Both counters were irradiated by the high-rate beam of the counting rates of 3−5 MHz. The plastic
scintillation and Čerenkov timing counters showed time resolution of ∼70 ps(rms) and ∼50 ps(rms) inthe high-rate condition, respectively. Although the baseline change by pile-up effects and performancesof the readout module made the time resolution worse than that of the low-rate condition, it was foundthat both counter satisfied the experimental requirements.

§ 1. Outline of the J-PARC E50 experiment

Investigation of the heavy quark baryon is a key way to understand a degree of freedom to describe

the hadron structure. The diquark correlation which is expected to be a degree of freedom of hadrons
can be studied from the spectroscopy of charmed baryons. An experiment to observe and investigate
the charmed baryons (J-PARC E50 [1]) was proposed at the J-PARC high-momentum beam line. The

56
experiment via the π − p → Yc∗+ D ∗− reaction at 20 GeV/c using the missing mass technique will be

performed for the systematic measurement of the excitation energy, the production rates and the decay
products of charmed baryons. From the systematic study of charmed baryons, the diquark correlation
which is expectedly an essential degree of freedom to describe the hadron structure can be revealed.
In the E50 experiment, the high-rate beam with a counting rate of 6.0×106 per beam extraction
cycle (2.0 seconds) is planned to be used due to a small production cross section of the charmed baryon
production. Therefore, the development of the high-rate detectors is one of the essential parts for constructing the spectrometer system.
1.1 Time zero counter
It is necessary to measure the 30 MHz beam for determining the beam timing as the reference starttiming by using a fine-segmented timing counter (Time zero counter: T0). T0 is required to have goodtime resolution of less than 100 ps(rms), while the its timing signal should be stable and fast response
for determining the start timing of many experimental apparatus in the high-counting rate condition.
For satisfying the requirements, the combination of a fine segmented plastic scintillator or an acrylicČerenkov radiator with MPPC can be a solution for T0. The maximum counting rate of the central
segment is expected to be ∼3 MHz when the horizontal segment of the 3-mm size is connected to the
3-mm squared MPPC. MPPC has good intrinsic time resolution of ∼200 ps(rms) for the one photoelec-tron detection [2] so that the time resolution of the counter is determined by the light yield and signal

response of the connected plastic scintillator and Čerenkov radiator. For confirming the performancesof T0, the test measurements with the combination of the plastic scintillator or Čerenkov radiator withMPPC were performed.
1.2 Scintillation ﬁber tracker
For measuring the beam tracks, it is necessary for tracking detectors to be satisfied under theoperation by assuming the beam with size of 100 mm(horizontal)×100 mm(vertical) and expecting total
counting rate of 30 MHz. This beam intensity is over the limit of the wire chamber operation so that ahigh-rate counters such as a scintillation fiber tracker are needed to handle the high-intensity beam. The
beam of 100 mm(H)×100 mm(V) is measured by the fiber tracker with a multi-layer configuration. The
counting rate per 1-mm segment is expected to 0.3−1 MHz from the total intensity of 30 MHz. In thiscondition, the time resolution of the fiber tracker for measuring the timing information with a narrow
timing gate is essential to suppress the accidental hits. It is required to have a resolution of 1 ns(rms)for selecting time gate in the tracking analysis. For confirming the time resolution of the scintillation
fiber counter, the test measurements with the combination of the scintillation fiber and MPPC were
performed.

57§ 2. First test of detector elements in November 2016

The performances of the detector elements were confirmed by using the low-counting rate beam andthe minimum ionization particle conditions. The experiment was performed as a parasite experimentwith the detector test for the J-PARC E40 experiment (Spokesperson: K. Miwa).
2.1 Test detector elements
For the test T0 counter, the fast timing plastic scintillator(EJ-228) and MPPC(S13360-3025PE)
were used. EJ-228 has both fast rise and decay time of 0.5 ns and 1.4 ns, respectively. The size of
scintillator was 3 mm(W) × 3 mm(T) × 150 mm(L). In the measurement, 3-mm squared MPPC with

25-µm pixels which has the fast rising time of 0.6 ns was used. MPPCs were attached to the both edge ofthe plastic scintillator. The number of detected photoelectrons by using this combination was ∼100 p.e.

from the measurement by using the 90 Sr source. Three test T0 counters were used in order to measure
Time-Of-Flight.
For the fiber counter, the multi-cladding scintillation fiber(SCFS-78M) and MPPC(S13360-3025PE)
were used. The diameters of fibers of φ1.0 mm and φ0.5 mm were used. The length of fibers were 500
mm and 300 mm for the φ1.0-mm and φ0.5-mm fiber, respectively. In this measurement, 3-mm squared
MPPC with 25-µm pixels was used. MPPCs were attached to the both edge of the scintillation fiber. The
number of detected photoelectrons by using this combination was ∼15 p.e. from the measurement byusing the 90 Sr source.

For the MPPC signal readout, a shaping amplifier which has a fast operational amplifier(AD8000)
was used. The detail of the MPPC amplifier is shown in Ref. [3]. The output signal from MPPC is shaped
to be the narrow signal with the time width of less than 10 ns.
For the Time-Of-Flight measurement, the reference counters were also used. The counters consistedof the fast timing plastic scintillator(EJ-228) and a metal packaged photomultiplier(R9880U). The sizeof the plastic scintillator was 3 mm(W) × 3 mm(T) × 30 mm(L) and they were stagged in parallel forcovering the 6-mm region. PMTs were attached to the both edge of the plastic scintillator.
2.2 Experimental conditions

The experiment was performed in the test beam line in the GeV-γ building of the Research Center
for Electron Photon Science(ELPH). The positron beam energy was 600 MeV. The experiment was performed as a parasite experiment so that the beam rate was changed during the beam time. Although
the beam rates of 1−150 kHz were used in the experiment, the rate dependence of the test counters was
negligibly small. The counting rate of each counter was measured to be less than 10 kHz because thesize of counter is smaller than that of beam.
All detectors were installed along the beam line. The reference counters were installed at the most
upstream and downstream of the experimental setup. The test T0 and scintillation fiber counters were
installed between the reference counters. The timing coincident signal from the reference counters wasused for the DAQ trigger signal. Timing and charge information from the counters were measured by

58

Fig.1. The correlation between TOF of a reference counter and a test T0 counter and
ADC before the pulse height correction.
The fitting function is shown by the redline.

Fig.2. The correlation between TOF of a reference counter and a test T0 counter and
ADC after the pulse height correction. It
was corrected by using the fitting function.

CAEN TDC(V775) and ADC(V792), respectively.
The dependences of signal threshold, operation voltage of MPPC and beam position were measured.
For measuring the signal threshold dependence, the output signals from the counter were discriminatedat the 7%, 10% and 15% level of the pulse height of the minimum ironization signal. In order to check
dependence of operation voltage of MPPC, the over voltage of MPPC(Vover ) was changed from 5 V to 13
V by ∆V = 2 V step. For the test T0 counter, the position dependence was checked by changing the beamirradiated positions. by changing height of the counter frame.
2.3 Analysis
The time resolution of each counter was obtained by using the Time-Of-Flight (TOF) method. The
signals were measured at the both edge of counters so that the mean time of each counter was used
for the TOF measurement. For obtaining the time resolution of the test T0 counter, combinations ofboth three test T0 counters and reference counters with one of the test T0 counters were used. In thecase of the scintillation fiber counters, the combination of the reference counters and one of the fibercounters was used. From the timing information of three combinations of mean times, the intrinsic time
resolutions of each counter were obtained.
For measuring TOF, the pulse height dependence of timing was corrected by using the correlation
between TOF of two counters and the ADC information. In the correction, two types of correction functions were used. For the correction of the reference counters and counters with MPPC,f (DE) = a + √b+ cln(DE) + d(DE), where DE = ADC − pedestal
DE

(1)

59

Fig.3. Time resolution of the T0 counters. The
horizontal and vertical axis show thetime resolution (rms) and over voltage of
MPPC, respectively. Blue, red and green
points show the time resolution of eachcounter.

Fig.4. Time resolution of the T0 counters. The
horizontal and vertical axis show thetime resolution (rms) and signal threshold, respectively. Blue, red and green
points show the time resolution of eachcounter.

andf (DE) = a + √b+ cln(DE), where DE = ADC − pedestal
DE(2)were used, respectively. Figure 1 and Fig. 2 show the correction of the pulse height dependence of the one
test T0 counter. Around the energy deposit region by the minimum ionization particle, the correlation
was clearly corrected.
The time resolutions of the T0 counters were obtained as a standard deviation of the TOF peak byfitting the Gaussian distribution. On the other hand, the resolutions of the scintillation fiber counterswere obtained as full width half maximum the TOF peak. The Time-Of-Flight peak of the scintillation
fiber counters had a tail so that the two Gaussian distributions were used for the fitting. For estimatingtime resolution, we adopted the full width half maximum of the TOF peak.
2.4 Results
2.4.1 T0 counter
Figure 3 shows the time resolution of the T0 counters. The time resolution of 72 ps(rms) was
obtained at Vover = 13 V. From the Vover dependence, the time resolution was improved by increasing
operation voltage because the photon detection efficiency is increased at the higher Vover . The time
resolution was improved by changing the signal threshold to be lower values as shown in Fig. 4. Aroundthe 10%-threshould region, there were no drastical improvement of resolution.
By checking the beam irradiated positions, it was fond that the difference of time resolution was lessthan 4 ps so that there was no position dependence along the plastic scintillator as shown in Fig. 5. In the

60

Fig.5. Time resolution of the T0 counters. The horizontal and vertical axis show the time resolution (rms) and signal threshold, respectively. Blue, red and green points show the time
resolution of each counter.

spectrometer system for the charmed baryon spectroscopy experiment, the difference of time resolution
is negligible small to identify the scattered particle by calculating mass squares with the Time-Of-Flightinformation. From the results from the time resolution dependence of over voltage of MPPC, signal
threshold and beam irradiated position, the requirement of the time resolution of less than 100 ps(rms)
was achieved.
2.4.2 Scintillation ﬁber counterAs shown in Fig. refFig06, the time resolutions of 650 ps(FWHM) and 1050 ps(FWHM) were obtained at Vover = 11 V for the φ1.0-mm and φ0.5-mm fibers, respectively. From the Vover dependence,
the time resolution was improved by increasing operation voltage because the photon detection efficiency
is increased at the higher Vover . The time resolution was improved by changing the signal thresholdto be lower values as show in Fig 7 and Fig 8. In the case of the fiber counter, the fixed values of signal threshold were used. The minimum threshold value corresponded to the 15−20% of the maximum
pulse height. Around the 10-mV threshold region, there were ∼5% improvement of time resolution. It

is confirmed that the time gate of 1 ns can be applied in the tracking analysis to suppress the accidental
hits.
2.5 Summary of the ﬁrst test experiment
By using the combination of the fine segmented plastic scintillator of 3 mm(W) × 3 mm(T) × 150

mm(L) and 3-mm squared MPPC which is installed on the fast signal shaping amplifier, it was found forthe time resolution of ∼70 ps(rms) by the means of the Time-Of-Flight measurement. The required time

61

Fig.6. Time resolution of the fiber counters. The horizontal and vertical axis show the time
resolution (rms) and over voltage of MPPC, respectively. Red and blue points show thetime resolution of counter with the φ1.0-mm and φ0.5-mm fibers, respectively.

resolution of less than 100 ps(rms) was achieved by taken into account the dependence of over voltage of
MPPC, signal threshold and beam irradiated position. The performances of the φ1.0-mm and φ0.5-mm
scintillation fiber counter with a 500-mm and 300-mm length show a time resolution of ∼650 ps(FWHM)

and ∼1050 ps(FWHM) at Vover = 11 V, respectively. For suppressing the accidental hits in the tracking
analysis, the required time resolution of 1 ns was achieved.

§ 3. High-rate test of detector elements in October 2017

For the second experiment, the detector elements were irradiated by a high-rate rate beam up to 5

MHz. We evaluated the performances of the time resolution of the test T0 counters by changing beam
rates. The preliminary results of the test T0 counters were reported in the second half of the annual
reports.
3.1 Test detector elements
The test T0 counters consisted of combinations of a plastic scintillator and an acrylic Čerenkov
radiator with MPPC. For the test scintillation counter, a fast timing plastic scintillator(EJ-228) andMPPC(S13360-3050PE) were used. The size of scintillator was 3 mm(W) × 3 mm(T) × 150 mm(L). The

plastic scintillators were perpendicularly installed to the beam direction and MPPCs were attached tothe both edge of the plastic scintillator. For the test Čerenkov counter, an acrylic (PMMA: Polymethyl
methacrylate) Čerenkov radiator and MPPC(S13360-3050PE) were used. We used two types of acrylic
shapes, called ”Bar-type” and ”X-type”. Bar-type is just acrylic bar with size of 3 mm(W) × 3 mm(T)× 150 mm(L) and 1 mm(W) × 3 mm(T) × 150 mm(L). The acrylic bar is tilted 48 degrees to the beamaxis so that Čerenkov photons reach MPPC placed at an edge of the bar by the shortest path. The
number of detected photoelectrons by using this combination was ∼25 p.e. at the center of radiator fromthe measurement by using the beam of β ∼1. X-type which is a ”Cross Shape” acrylic was cut from62

Fig.7. Time resolution of the φ1.0-mm fibercounters.
The horizontal and vertical axis show the time resolution (rms)and over voltage of MPPC, respectively.
Blue, red and green points show the time
resolution of each signal threshold value.

Fig.8. Time resolution of the φ0.5-mm fibercounters.
The horizontal and vertical axis show the time resolution (rms)and over voltage of MPPC, respectively.
Blue, red and green points show the time
resolution of each signal threshold value.

an acrylic board having size of 3 mm(W) × 3 mm(T) × 150 mm(L) for one side. The opening angle ofcross from the beam axis was 48 degrees. MPPCs were attached to the downstream of both edge of the
X-type radiator for measuring Čerenkov photons which reach MPPCs by the shortest path. The numberof detected photoelectrons by using this combination was ∼50 p.e. at the center of radiator from themeasurement by using the beam of β ∼1. For the MPPC signal readout, a shaping amplifier which has

a fast operational amplifier(AD8000) was used as described in the Sec. 2. The shaping amplifier was
modified to suppress the overshoot after the signal for adding the pole-zero cancellation resistance of390 Ω on the circuit for 50-µm pixel MPPC(S13360-3050PE).
For the Time-Of-Flight measurement and making the DAQ trigger signal, two reference counterswere also installed at the most upstream and downstream, respectively. The counters consisted of thefast timing plastic scintillator(EJ-228) and a metal packaged photomultiplier(R9880U). The size of theplastic scintillator was 3 mm(W) × 6 mm(T) × 30 mm(L). PMTs were attached to the both edge of theplastic scintillator.

In total, 1 plastic scintillation and 3 Čerenkov counters having different shapes were installed.
Time resolutions were evaluated from the Time-Of-Flight measurement by using combinations of thosecounters and reference counters.
3.2 Experimental conditions
The experiment was performed in the second experimental room in the the Research Center forElectron Photon Science(ELPH). Detectors were installed at the downstream of the beam extraction
points to the GeV-γ building. For the experiment, the electron and positron beams converted from theextracted γ rays by the 1-mm thick Aluminum cover of the beam pile flange were used. Beam rates were
adjusted from the beam current of the accelerator up to 2 MHz/3 mm segment conditions. For obtaining

63

Cherenkov counters
Bar-type
Plastic
Scintillator (3 mm, 1 mm) X-type
Ref 1

MPPC + Amp
Fiber tracker
Ref 2

Beam
e+ / e-Fig.9. Experimental setup.

more than 3 MHz/3 mm segment conditions, the additional 1-mm thick Aluminum plate was installed on
the cover of the beam pile flange, and the beam extraction cycle was changed to be ∼6 seconds from theusual cycle of 10 seconds. For checking the counting rates of the counters, the visual scaler values in the
counting room ware roughly measured. In the analysis, the event-by-event scaler values measured by
the HUL module [4] were used for determining counting rate of each counter. The hit rate (counts/sec.)of each detector was calculated by running mean in every 200 mseconds to avoid fluctuation caused bydead time of DAQ.
All detectors were installed along the beam line as shown in Fig 9. The reference counters were
installed at the most upstream and downstream of the experimental setup. The test T0 counters were
installed among the reference counters. The timing coincident signal from the reference counters wasused for the DAQ trigger signal. Timing and pulse height information from the counters were measured
by the DRS4 module [5] in which a FPGA based High-resolution TDC (HR-TDC) is implemented. The
DRS4 module can measure both waveform of input signal and timing signal by discriminator. For obtaining the TOF information, the discriminator signals measured by HR-TDC were used. The waveform
information was only used for measuring signal pulse heights for the pulse-height correction and analyzing pile-up effects in the high-rate conditions. The discriminator output signals from DRS4 were used
for scalers measured by the HUL module.
For evaluating performances in the high-rate conditions. signal thresholds of 10% level of the pulse
height of the minimum ironization signal and 3.5 photoelectrons were used for the scintillation andČerenkov counters, respectively. The over voltage of MPPC(Vover ) of 7V was used for the test.
3.3 Analysis
Figure 10 shows the pulse height distribution of the Čerenkov counters. The contribution fromthe multi-particle hits were small enough. For obtaining the time resolution of the minimum ionization
particle conditions and one particle hit condition. of the scintillation and Čerenkov counters, respectively,
the higher pulse height events were not used.
The time resolution of each counter was obtained by using the TOF method. In the case of the plastic
scintillator and the X-type Čerenkov counters, the signals were measured at the both edge of counters64

Fig.10. Pulse height distribution of the Čerenkov counters. (a) and (b) show pulse heights of the
1-mm and 3-mm width Bar-type Chrenkov counters. (c) and (d) show pulse heights of
top and bottom of the X-type Chrenkov counters, respectively.

so that the mean time of each counter was used for the timing measurement. In the case of the bar-typeČerenkov counters, the signals were measured at one edge of counters. Then, the TOF information was
obtained by using the mean times of each counter. From the timing information of three combinations ofmean times, the intrinsic time resolutions of each counter were obtained. The combinations between the
scintillation counters and reference counters, and between each Čerenkov counter were actually used
for the evaluation of the time resolution.
For measuring TOF, the pulse height dependence of timing was corrected by using the correlation
between TOF of two counters and the pulse height information. For the correction of the scintillation
and Čerenkov counters,f (P H) = a + √b+ cln(P H),
PH(3)

f (P H) = a + √

b
,
PH

(4)

and

were used, respectively, where ”PH” means pulse height measured by the waveform from DRS4.
The event-by-event counting rates of each counter were measured by the HUL scaler. Figure 11
shows the distributions of the event-by-event counting rates of the 3-mm width Bar-type Čerenkov
counter. Each distribution shows the counting rate conditions of the average rate of 0.5, 1.5 and 3.0

65

Fig.11. Distributions of the event-by-event counting rate of the 3-mm width Bar-type Čerenkov
counter. (a), (b) and (c) show the counting rate conditions of the average rate of 0.5, 1.5
and 3.0 MHz/3-mm segment, respectively.

Fig.12. Time resolution by changing counting rate conditions. Horizontal error bars show therange of the counting rate by selecting event-by-event scaler counts.

MHz/3-mm segment. From the distributions of the counting rate of each counter, we selected 5 regions
for evaluating the time resolution.
Figure 12 shows the time resolution of each counter by changing the counting rate conditions. Horizontal error bars show the range of the counting rate by selecting event-by-event scaler counts. The
result shows that the time resolution of all counters achieved that of less than 70 ps up to 5 MHz. In
particular, the X-type Čerenkov counter showed the best time resolution of ∼50 ps(rms) in the range of

3−5 MHz. In addition, the 1-mm width Bar-type Čerenkov counter showed the same time resolution asof the 3-mm width Bar-type Čerenkov one. It can be explained by the detection of the same number ofphoton by MPPC without loss by reflection in the PMMA radiator. It means that the total beam rate canbe increased when the 1-mm width Čerenkov counters are used. We found that it is possible to use 3
time higher beam in the E50 experiment by using the 1-mm width Čerenkov counters.

66

Fig.13. Waveform sample of the 3-mm Bar-typeČerenkov counter at the high-counting
rate condition. Signals having events
whose timings were 50 ns before thetrigger timing was taken as a pile-up
event.

Fig.14. Time resolution of the 3-mm width
Bar-type Čerenkov counter by selecting pile-up events. Black, blue and red
points show the time resolutions of all
events, of pile-up events and without
pile-up events, respectively.

The time resolutions became worse by increasing counting rates. Figure 13 shows a waveform sample of the 3-mm Bar-type Čerenkov counter at the high-counting rate condition. From the waveform, thebaseline of the trigger timing signal having a pile-up event was affected. Although the signal overshoothad been corrected by implementing the pole-zero cancellation resistance, the ringing pulses after thesignal still remained in the overshoot region. For evaluating the effects from the baseline change by thepile-up, signals having events whose timings were 50 ns before the trigger timing was taken as a pile-up
event. Figure 14 shows the time resolutions by selecting the pile-up events. By increasing the counting
rates, the time resolution became worse. For explaining the dependence of the time resolution in Fig. 14,
a base-line shift by pile-up signals causes in part. Response of the amplifier in the DRS4 module may
have a rate dependence and affects the time resolution. Even if the time resolution is deteriorated bypile-up, the time resolution (∼50 ps) better than required on (100 ps) is achieved by using the X-typeČerenkov counter.
3.4 Summary of the second test experiment
The timing counters consist of the combination of a plastic scintillator and an acrylic Čerenkov
radiator with MPPC were tested by using the high-counting rate beam by the ELPH facility. By irradiating high-rate beams up to 5 MHz, we found that all counters showed the time resolutions of less than70 ps(rms). The requirement of the time resolution of less than 100 ps(rms) have been achieved in thehigh-rate condition even if the time resolution was made worse by pile-up effects and the performancesof the DRS4 module. In particular, the Čerenkov counter having ”Cross Shape”, called X-type, showed
the best time resolution of ∼50 ps(rms) at 3−5 MHz. Therefore, the X-type Čerenkov counter can be thecandidate to use the T0 counter for the J-PARC E50 experiment.

67

Acknowledgment
We would like to acknowledge the outstanding efforts of the staff of the Research Center for Electron
Photon Science. We also acknowledge the J-PARC E40 experimental group for accepting to join the test
experiment.

References[1]

H. Noumi et al .: J-PARC E50 Proposal (2012).

[2]

Opto-Semiconductor Handbook, Hamamatsu Photonics K.K.

[3]

T. Nishizawa et al ., IEEE TNS 61 (2014) 1278.

[4]

R. Honda et al ., http://openit.kek.jp/project/HUL[5]

T. N. Tomonori et al ., Annual Report 2016 ”Development of a FPGA-based high resolution TDC
using Xilinx Spartan-6”

68

ELPH Annual Report, Tohoku University (2017)(ELPH Experiment : #2876)

Performance of a shower depth measurement method
for the KOTO CsI calorimeter
N. Hara1 , K. Kotera1∗, T. Mari1 , H. Nanjo1 , H. Nishimiya1 ,Y. Sato1 , N. Shimizu1 , Y. Tajima2 , T. Yamanaka1
1

2

Department of Physics, Osaka University, Toyonaka, 560-0043, Japan
Department of Physics, Yamagata University, Yamagata, 990-8560, Japan

Abstract
We plan to upgrade the J-PARC KOTO CsI calorimeter to distinguish photons and neutrons.
Before the upgrade, we tested a prototype detector to confirm that the upgraded calorimeter
will have an expected performance at the KOTO experiment.

1

Introduction

The aim of KOTO experiment [1] is to search for a CP-violating neutral kaon decay mode,
KL → π 0 ν ν̄. Because the branching ratio predicted by the standard model (SM) is small(3 × 10−11 ), the decay mode is sensitive to new physics beyond the SM. The signature ofthis decay mode has only two photons from a π 0 decay without any other observable particles.
Figure 1 shows the KOTO detector. The decay volume shown in the figure is surrounded by acalorimeter [2] and veto counters. The calorimeter measures the energies and hit positions of
the two photons, and veto counters detect particles from the background events.

Figure 1: Cut-out view of the KOTO detector assembly. CsI calorimeter is illustrated in red.
The calorimeter is composed of 2716 un-doped CsI crystals stacked inside a 1.9 m diameter
cylinder. The central 1.2× 1.2 m2 region is filled with 2240 of 25 × 25 × 500 mm3 crystals (small
crystals). The outer region is filled with 476 of 50 × 50 × 500 mm3 crystals (large crystals).
Each crystal is read out with a photo-multiplier tube (PMT) attached on its rear surface.
One of the major backgrounds is caused by neutrons directly hitting the calorimeter, making
two photon-like clusters. Such events can be rejected if the calorimeter can distinguish between
photon clusters and neutron clusters. In addition to rejecting the neutron–induced clusters withthe cluster shapes and waveforms, we plan to further reject them by measuring their shower
depths. While photons make showers in shallow region, neutrons can make showers at any∗

corresponding authoer: coterra@champ.hep.sci.osaka-u.ac.jp

69
depths. To measure the shower depths, we will attach silicon photomultipliers (SiPMs) on thefront surface of CsI crystals and measure the timing difference between the SiPMs and PMTs.
We have already confirmed that this shower depth measurement method can reduce theneutron background events by more than a factor of 10, even after applying cuts on cluster
shapes and waveforms. To confirm the above, we had several bench test, a test beam experimentwith neutron and photon mixed beams at the Research Center for Nuclear Physics in Osaka, anda set of simulation studies [3]. After above studies, we have established a method to glue SiPMs
on crystals and readout circuits that we will actually use for the KOTO calorimeter. In theexperiment reported in this note, we tested these established methods with a small prototype
calorimeter to confirm the feasibility of the shower depth measurement, and to measure thetiming and energy resolutions under several conditions with the ELPH position beams.

2

Setup

Figure 2 shows a schematic view of the stacked crystals tested at ELPH. It was 3 × 3 of large
crystals surrounding 2 × 2 of large crystals. As shown in Fig. 3, the detector was placed on aturn table and this table was movable in the horizontal and vertical directions. This setup wasplaced in a tent with a relativistic humidity of less than 25%. Figure 3 also shows a set of three
scintillator counters used to trigger on positrons hitting the CsI crystals in a 10 × 10 mm2 area.
On the upstream side of the crystals, we attached SiPMs called Multi-pixel photon counter(MPPC) produced by Hamamatsu K.K. (S13360-6050CS). It has a 6 × 6 mm2 sensitive area
covered with silicone which is transparent to the ultraviolet (UV) scintillation light (310 nm)
from the CsI crystals. One MPPC was used for each small crystal, and four MPPCs were used
for each large crystal. The MPPCs were glued on 0.5 mm thick quartz plates which were thenglued on the CsI crystals as shown in Fig. 4. This method solves a difficulty to glue the MPPCs
with concaved silicone windows on flat crystal surfaces.

Figure 2: A stack of CsI crystals with MPPCs and PMTs. Each crystal was wrapped with a foil.
The signals from four MPPCs on a single large crystal or four small crystals are merged
together to reduce the number of channels and materials of cables in front of the CsI calorimeterin the update design. We had two candidate methods to connect the four MPPCs: (a) the

70

e
b

f
c

g

a

h

i
j
x

d
y

z

Figure 3: Schematic of beam setup. a: the end of the beam pipe, b: trigger counter to define timing, cand d: trigger counters for defining beam positions (10.0 × 10.0 mm2 ), e: x-y moving stage, f: turn table, g:
detector frame, h: MPPCs, i: CsI crystals, j: PMTs.
MPPC biases are applied in parallel and signals are read out also in parallel (parallel), and(b) the MPPC biases are applied in parallel whereas the high frequency signals are readout inseries (hybrid). The latter method was developed for the MEG II upgrade [4]. Figure 5 a) andb) show those two methods. The parallel method has an advantage that the circuit is simple,
whereas the pulse becomes wider; the hybrid method makes sharper signals, but the circuit ismore complicated. We thus compared the resolutions of timing difference between PMT and
MPPCs for the positron showers between those two methods in this study. Moreover, four
signals from four of those combined MPPCs were read out together using summing amplifiers
as shown in Fig. 5 c) to reduce the number of channels. The signals from the amplifiers weresent to 125 MHz waveform digitizers used for the KOTO detector [5].
To calibrate the timing differences between the MPPC and PMT as a function of the scintillation position, six sets of cosmic trigger counters were located above and below the test
detector.

3

Detector configurations

The following detector parameters were changed during the beam time for our studies.
1. The four–MPPC connection methods among “parallel”, “hybrid” and single readout
2. Combinations of CsI crystals for summing amplifiers
3. Beam position, direction, and momentum
4. MPPCs with and without irradiation 1
These parameters were changed for eight large crystals and four small crystals in several
detector configurations for various aims. Figure 6 lists the configurations taken during our threedays of run time. In addition to the lists, the beam momentum was scanned in four steps; 200,
400, 600, and 800 MeV/c for each configuration.

1

The dark current of MPPCs increases proportionally to the irradiation. We prepared MPPCs irradiated withneutrons equivalent to 1.5 times the maximum irradiation estimated for the KOTO running period. The dark current
increased by a factor of 100 with the irradiation.

71

a)

c)

b)

d)

Figure 4: MPPCs glued on quartz plates. a) for small crystal, b) backside view with baseboards for small
crystal, c) for large crystal, d) backside view of MPPCs on a crystal without the baseboard to show Alardaitearound the edges of MPPCs (see text).

4 A preliminary result: Effect of irradiation on MPPCs
on the timing resolution
Figure 7 shows the timing resolutions as a function of deposited energy in a crystal. Thereis no significant difference between the MPPCs with and without the irradiation. We thus
concluded that the irradiation during the KOTO running has no effect on the performance ofthe shower depth measurement method to distinguish neutron showers from photon showers.
We also concluded that the MPPC gluing method is feasible, the hybrid connection has better
performance than the parallel connection, and the summing amplifier works as expected. The
results of other on-going studies will be reported elsewhere.

References[1] J. K. Ahn et al., (J-PARC KOTO Collaboration), PTEP, 2017, 021C01 (2017).
[2] E. Iwai et al., Nucl. Instrum. Meth. A, 786, 135 (2015).
[3] H. Nishimiya, Master thesis, Osaka University (2018) written in Japanese.
[4] A.M. Baldini et al., Eur. Phys. J. C, 78: 380 (2018).
M. Ogawa, Master thesis, the University of Tokyo (2016) written in Japanese.
[5] Y. Sugiyama et al., IEEE Trans. Nucl. Sci., 62, 1115-1121 (2014).

72

a)

b)
r

r

2r r

r

2r

MPPC

readout

readout

four MPPCsc)

Figure 5: MPPC signal driving circuits. a) parallel connection, b) hybrid connection developed by MEGII
collaboration, c) summing amplifier.

12/9

Cosmic runs forcalibration.

to see performance ofsummed signals: beam
hit the large crystal sideof center of summed
crystals.
MPPC=hybrid connection
to see performance ofsummed signals: beam
hit the small crystal sideof center of summed
crystals.
MPPC=hybrid connection
to see performance ofthe other group ofsummed signals.
MPPC=hybrid connection

12/11

Test 11-0
cosmic ran for
calibration.

Test 11-1
to see performance ofparallel connection(MPPCs on small
crystals were connectedin parallel).
Test 11-2
to compare with fourPMMC connected case,small crystals wereindividually read out.

Test 11-3
to see sensitivity to theincident angle, detector
was tilted toward thebeam. φ=10
x=-20, 12.5, 5, y=0

12/12

Test 12-0
cosmic run for
calibration.

Test 12-1
L1, L2, L3, and all
MPPCs for small crystals
were MPPCs
irradiated(see text).

Test 12-2
beams were injectedfrom the PMT side.

Test 12-3
to see the effect ofirradiation on MPPCs,
L1, L2, L3, and all
MPPCs for small crystals
were MPPCs
irradiated(see text).

L0

L1

L2

0

1

L7

3

2

L6

L5

L0

L0

L3
L4

L1

L2

0

1

L7

3

2

L6

L5

L0

To see performance of
seamless crystal (L0crystal is a seamlesscrystal (see text)

To see performance of
single large crystal.

L3
L4

L1

L2

0

1

L7

3

2

L6
L0

Cosmic runs forcalibration.

L1

L2

0

1

L7

3

2

L6

L5

L0

L1

L2

0

1

L7

3

2

L6

L5

L4

L0

L1

L2

0

1

L7

3

2

L5

L4

L6

L5

L1

L2

0

1

3

2

L6

L5

0

L7

3

L6

L5

0

L7

3

L6

L5

2

0

L7

3

L6

L5

0

L7

3

L6

L5

L0

2

2

L4

L3

L2

L3

L2

1
2

L3
L4

1

3

2

L6

L5

L2

L3

0

Test 11-5
dato compare with test
11-1, MPPCs on small
crystals were connecte
in hybrid.

0

1

L7

3

2

L6

L5

L2

L3

Test 11-6
to see performance ofreadout withoutsumming amplifier.

0

1

L7

3

2

L6

L5

L2

L3

0

1

L7

3

2

L6

L5

L2

L3
L4

L5

L0

L1

L7

3

L6

L5

L7

3

L6

L5

0

Test 12-4
MPPCs were connectedin parallel for L6, to see
the effect on the large
crystal case.

3

L6

L5

L0

Test 12-5
same as the test 12-3,
but different injection
position.

sa

L2
1
2

L2

1
2

L3
L4
L2

1
2

L3
L4

0

1

3

2

L6

L5

L2

L3
L4

L1
0

1

L7

3

2

L6

L5

L2

L3
L4

L1
0

1

L7

3

2

L6

L5

L0

L3
L4

L7

L0

L3
L4

L1

L0

Test 12-6
to see the effect ofMPPCs on the energy
resolution of PMT, all
MPPCs were removed.

2

L1

L7

L2

1

L1

L0

L4
L1

L6

0

Test 11-6
to see timing response
to high energy beam(-800 MeV), beam was
injected from side face:
L0=seamless crystal,
L7=bonding two crystals.

Test 12-7
same as test 12-6, butdifferent injection
position.

3

L0

L4
L1

L7

0

L4
L1

L1

L0

L4

0

L0

L2

1

L7

L0

Test 11-4
to see sensitivity to theincident angle, incident
angle was scanned:
φ=20,30,40
x=-20, y=50

L4

L1

L0

L3

1

L1

L0

L2

L4

L1

L0

L3

L3

1

L1

L0

L3

L4
L1

L0

73

L4

L3

L7

L3

L2

L3
L4

L1
0

1

L7

3

2

L6

L5

L2

L3
L4

Figure 6: Run configurations and their aims on December 9th, 11th, and 12th data taking. Each color
shows crystals that were read out together with a summing amplifier. L0–L7 show ID of large crystals and
0–3 show ID of small crystals. Dots and allows show incidental positions of beams.

74

T resolution

2

no irradiation

T (ns)

1.5

irradiated1

Preliminary

0.5
0

0

200
400
600
deposited Energy (MeV)

800

Figure 7: Standard diviation of timing difference between MPPC and PMT as a function of depositedenergy. The 60 MeV data were measured with cosmic rays and rest were measured with positrons.

ELPH Annual Report, Tohoku University (2017)75(ELPH Experiment : #2881)

Search for an η d bound state by use of the γd → ηdreaction
H. Fujioka1∗ , T. Ishikawa2 , and T. Sekihara3
1
2
3

Department of Physics, Kyoto University, Kyoto 606-8502, Japan

Research Center for Electron Photon Science, Tohoku University, Sendai 982-0826, Japan

Advanced Science Research Center, Japan Atomic Energy Agency, Ibaraki 319-1195, Japan

Owing to an attractive interaction between an η  meson and a nucleus, the existence of an η  dbound state is theoretically predicted. We propose a novel method to investigate this system using thecoherent η phtooproduction off deuteron, i.e. γd → ηd, with the η meson emitted in backward angles.

The details are described in a published paper [T. Sekihara, H. Fujioka, and T. Ishikawa: Phys. Rev. C
97 (2018) 045202].

§ 1. η  meson at finite density

Properties of hadrons is subject to change at finite density, especially as a result of partial restora-tion of chiral symmetry. For example, the mass of an η  meson, which is approximately 958 MeV/c2 in
vacuum, may be reduced [1–3]. From a theoretical point of view, the mass of an η  meson, the largest
among the pseudoscalar meson nonet, is related to the UA (1) anomaly in QCD. This anomaly effect topush up the η  mass may suppressed at finite density due to partial restoration of chiral symmetry [4].
A mass reduction of an η  meson in a nucleus is equivalent to an attractive interaction between the η meson and the nucleus, which may lead to the existence of an η  -nucleus bound state, i.e. an η  -mesic
nucleus.
Experimental searches for η  -mesic nuclei are being carried out at GSI/FAIR [5], LEPS2 (SPring8) [6],and are planned at BGO-OD (ELSA) [7], with employing missing-mass spectroscopy for (p, d) or (γ, p)
reactions on nuclear targets. In general, the sensitivity of finding a peak structure corresponding to anη  -mesic nucleus in a missing-mass spectrum strongly depends on the decay width of the η  -mesic nucleus as well as the signal strength relative to the background level. We propose an alternative method
to investigate an η  -mesic nuclei via the s-channel formation [8], in which the background level will bevery small and a large decay width is expected not to be troublesome.

§ 2. η  d bound state via coherent η photoproduction off deuteron

If an η  d bound state does exist, it may be formed via the γd → [η  d]bound → ηd reaction, namely

the coherent η photoproduction reaction off deuteron. A detailed description and result of theoretical
calculations of the η  d bound state and the cross section of γd → ηd are given in Ref. [9].
∗Present address: Department of Physics, Tokyo Institute of Technology, Meguro 152-8551, Japan

76
While the “conventional” coherent process, where a quasi-free η production process (γN → ηN )is followed by a recombination of two nucleons into a deuteron, is significant in forward angles witha small momentum transfer, the decay of an η  d bound state into ηd will take place isotropically inthe center-of-mass frame. As a result, the background η production will be predominantly due to the[η  d]bound formation. Therefore, by looking into the center-of-mass energy dependence of the differential
cross section for backward η production, a lineshape of the η  d bound state can be obtained.

§ 3. Feasibility study of a new experiment with FOREST at ELPH

The η  d threshold of 2.833 GeV corresponds to the incident photon energy of 1.20 GeV. Therefore,

the near-threshold cross section of the γd → ηd reaction can be investigated with a tagged photon beamfrom the 1.3 GeV electron synchrotron.

While an η meson in the final state can be identified via its 2γ decay with the FOREST spectrometer,
the distinction between γd → ηd and γd → ηpn is mandatory; the latter mainly comes from a quasifree γN → ηN process with a non-negligible differential cross section for backward angles. It calls

for a new detector downstream of a liquid deuterium target with the capability of tracking and particle
identification. A study with a Monte Carlo simulation is in progress.

Acknowledgment
This work was partly supported by the Grants-in-Aid for Scientific Research from MEXT and JSPS
(No. 26400287 and No. 15K17649).

References[1]

H. Nagahiro and S. Hirenzaki: Phys. Rev. Lett. 94 (2005) 232503; H. Nagahiro, M. Takizawa, and
S. Hirenzaki: Phys. Rev. C 74 (2006) 045203.

[2]

S. Sakai and D. Jido: Phys. Rev. C 88 (2013) 064906; Prog. Theor. Exp. Phys. 2017 (2017) 013D01.

[3]S. D. Bass and A. W. Thomas: Acta Phys. Polon. B 45 (2014) 627.

[4]

D. Jido, H. Nagahiro, and S. Hirenzaki: Phys. Rev. C 85 (2012) 032201(R).

[5]

Y.K. Tanaka et al.: Phys. Rev. C 97 (2018) 015202.

[6]

N. Muramatsu: Few-Body Syst. 128 (2013) 997; N. Muramatsu et al.: ELPH Annual Report 2015
Vol. 6 (2015) 91.

[7]

V. Metag et al.: approved proposal ELSA/03-2012-BGO-OD.

[8]

H. Fujioka et al.: Letter of Intent ELPH-2881 (2017).

[9]

T. Sekihara, H. Fujioka, and T. Ishikawa: Phys. Rev. C 97 (2018) 045202.

ELPH Annual Report, Tohoku University (2017)(ELPH Experiment : #2884)

Development of an Aerogel Chrenkov Counter
with Efficient Light Collection
Hiroki Yamada, Nozomu Morita, Kunpei Matsuda, Masahiro Okabe,
Norihito Muramatsu
Research Center for Electron Photon Science, Tohoku University, Sendai 982-0826
We tested the methods to increase the Cherenkov light collection from an aerogel radiator (refractive
index = 1.05) to a photomultiplier tube (PMT) through a long air light guide. The test experiment was
performed by using a 600 MeV/c positron beam available at Research Center for Electron Photon
Science, Tohoku University. The detected light yields at the PMT were compared by changing reflecting
material sheets. Several wavelength shifting materials were also coated on the reflecting sheet surface
with a solvent to confirm the increase of the light collection. In addition, the dependence of the lightcollection on the beam injection angle was examined as a basic performance test. These behaviors wereconfirmed by a Geant4-based Monte Carlo simulation.

エアロジェル・チェレンコフ検出器の集光効率向上を目指した開発
山田悠樹 森田希望 松田薫平 岡部雅大 村松憲仁
東北大学電子光理学研究センター 〒 仙台市太白区三神峯 
§１．実験概要
63ULQJ/(36 ビームラインのソレノイド実験では、チェレンコフ検出器を置くスペースが非常に限られている。このように既にある設備の制限などによって放射体と光電子増倍管の距離を取らなければならない場合でも高い検出率を得るために、筐体内部の放射体と光電子増倍管の間の部分をエアライトガイドとして用いるというアプローチを試した。
またその結果について *HDQW を用いたシミュレーションと比較した。
 内側に張る反射材の工夫
どのような素材がチェレンコフ光の集光を高めるのに最適か、それらの特性について調
べた。反射特性による影響やシンチレーションの有無について調べた。

77

78

表 㻝㻌 試験した反射材の種類と特徴㻌
名称㻱㻿㻾㼀㼑㼒㼘㼛㼚㻔㻝㻜㼘㼍㼥㼛㼞㻕㻳㼛㼞㼑㻙㼀㼑㼤

㼀㼥㼢㼑㼗

銀反射シート

アルミシート素材

ポリエステル系

㻼㼀㼀㻱㻛ポリテト

延伸 㻼㼀㻲㻱 膜

高密度ポリエ銀

アルミ

樹脂

ラフルオロエチ

チレン不織布

レン

反射率

㻥㻤㻚㻡㻑

㻥㻢㻑

㻥㻥㻑

㻣㻜㻑

㻤㻡㻑

㻣㻤㻑

反射特製

鏡面反射

拡散反射

拡散反射

拡散反射

鏡面反射

鏡面反射

あり

なし

なし

なし

なし

なし

㻟㻤㻜㻌㼚㼙 以下で重ねるほど、短短波長から長反射率は低いあまり試されて反射率は低い

反射率が著しく

波長ほど、優れ波長まで高いが、紙状で加いない。

が、波長による減衰。

た反射率を示反射率を保つ工しやすい。

す。

が高価。

シンチレー
ション
特徴

影響は小さい。

 波長変換剤
チェレンコフ光は紫外領域の発光強度が大きく、この部分の光電子増倍管の感度がよくない。そこで波長変換剤を反射材上に塗布して用いることで、放出光を可視光領域に変換して集光・検出効率を上げられないか実験した。
表 Ϯ㻌 反射材に塗布した波長変換剤の種類と特徴

吸収波長 (nm)発光波長 (nm)POPOP308-337407-454

PPO

248-337359-391

BPBD

266-337341-392pT

248-308322-364

TPB

128-250

400-460

薬品名㻌

構造

79

図  実験セットアップ§２．データ収集
今回の実験は、エアロジェルから出るチェレンコフ光の量の変化を確認するものである。
実験では東北大学電子光理学研究センターの陽電子ビーム（運動量  0H9F）を使用した。図  に示すように、PP 厚の同じエアロジェル（屈折率 ）を  つ重ねて使用し、筐体と垂直（°）、°、°（筐体に付けている光電子増倍管と逆側）からビームを入射した。今回作成したデータ収集系のブロック図は図  の通りである。陽電子ビームによって出たチェレンコフ光であると判断するために、今回の実験で用いた筐体の前にビームポ
ジションモニターを置いた。そこからの信号がある場合のみトリガー信号を作成し、それによるゲート信号に入ったチェレンコフ光の量を $'& で測定した。ビームポジションモニタ
ーの信号を 7'& で測定し、同期した信号を見ているかオフラインで確認した。

図  データ収集系のブロック図

80§３．データ解析 解析手法
今回の実験は、反射材及び波長変換剤を変化させることで集光効率の改善を試みた。また、集光効率のビーム入射角度による依存性を確認した。
具体的には、以下の光量を比較した。
 反射材による違い

𝑦𝑦𝑦𝑦𝑦𝑦𝑦𝑦𝑦𝑦 = 𝑚𝑚𝑚𝑚𝑚𝑚𝑚𝑚 𝑜𝑜𝑜𝑜 𝐴𝐴𝐴𝐴𝐴𝐴 𝑣𝑣𝑣𝑣𝑣𝑣𝑣𝑣𝑣𝑣𝑣𝑣 − 𝐴𝐴𝐴𝐴𝐴𝐴 𝑝𝑝𝑝𝑝𝑝𝑝𝑝𝑝𝑝𝑝𝑝𝑝𝑝𝑝

結果は図３に示す。図から分かるように \LHOG が最も優れていたのは (65 で だった。また、鏡面反射と拡散反射では有為な差が得られなかったが反射率による依存性は見られ、反射率が上昇するごとに \LHOG は指数関数的に向上している 図４参照 。ただし、*RUH7H[ のみは相関から大きく外れた結果を見せた。また、計算によって求めた光電子数と図４の対応関係より、$'&&KDQQHO と光電子数の関係式を導いた。
光電子数 = 0.083 × ADC Channel

図３ 反射材ごとの \LHOG：紫が拡散反射、オレンジが

図４ \LHOGYV 反射率

鏡面反射の反射材で、反射率の良い物ほど左に並べた。

 波長変換剤による違い
結果は図５に示す。全ての波長変換剤で、塗布した筐体が塗布しない筐体に比べて有為に優れた集光効率を見せた。最も向上したのは 73% を塗布した筐体で、\LHOG が  倍になった。
 角度依存の結果
結果は図６に示す。また、筐体の角度による影響のみを見るため、ビームがエアロジェ
ルを通る厚さによる生成光子数の増減と透過長による影響を考慮して、エアロジェルの厚さを  度のときにそろえる補正をかけた結果も並べてある。
結果から分かるように  度と  度のときはほとんど変わらないが  度のときに \LHOG
が  倍に向上していることが分かる。これは、 度のときが最も反射回数を抑えられているからだと考えられる。

81

図５ 波長変換剤ごとの \LHOG：一番左が何も塗布していない筐体。

図６ 角度ごとの \LHOG

§４．モンテカルロ・シミュレーション*HDQW を用いて、実験での反射材比較と光量の角度依存の結果を、モデル化したシミュ
レーションで理解できるか確認した。特に、実験では生成光子数を測ることが出来ない点を補う。条件として、反射材の性質 反射率と反射の種類 、筐体とエアロジェルの配置、陽電子ビームの方向を指定した。
 角度依存シミュレーション
エアロジェルに対して陽電子ビームが図７左のような方向から入射することを考えた結果、図７右のような結果が得られた。

図７ シミュレーションによる光量の入射角度依存性
エアロジェルを陽電子が通過する距離が長いほど多くの光子を放出すると考えられるので、°、°、°に生成光子数が多くなる。角度変化により光路も変化し、反射回数は
°、°、°の順に 、、 回であった。反射回数が少ないほど減衰も少ない。

82 反射材比較シミュレーション 各反射材について角度 °で入射したとき
図８のような結果になった。反射率と集光率には相関があることが分かったが、鏡面反射と拡散反射では有意な差は見られなかった。
 また、どの反射材でもイベントの検出効率はだった。実験では検出できないイベントが多いことから筐体の隙間や反射材のゆがみによる影響が大きいと考えられる。

図  シミュレーションによる反射材の比較

ELPH Annual Report, Tohoku University (2017)83(ELPH Experiment : #2889)

Development of Electro-magnetic Sampling Calorimeterwith Active Absorbers
Y. Hasegawa1 , H. Ishihama1 , H. Sato2 , T. Takeshita1 , R. Terada1 ,Y. Yamashita1 , and Y. Yoshimura1
1
2

Faculty of Science, Shinshu University, Matsumoto, Japan

Institute of Particle and Nuclear Studies, KEK, Tsukuba, Japan

High performance sampling calorimeter is indispensable for physics measurement at collider experiment and its performance improvement is very important. We made electro-magnetic calorimeterwith optical readout from absorber material and tested with positron beam at ELPH at Tohoku University. This calorimeter obtains high performance by acquiring information on the absorption layer usingtransparent lead glass that can detect Cherenkov light of the absorber with photosensor. In this report,
performances of this calorimeter are presented.

§ 1. Introduction

We are developing full active electro-magnetic calorimeter consisting of active absorption layers andvery fine granualte detection layers. The lead glass calorimeter has good energy resolution by energy
measurement of electrons and photons, and similarly reads out the absorption layer of lead glass to
obtain dramatically higher performance than ordinary sampling calorimeter. In addition, it has a highposition resolution of incident photons and electrons due to the high granulated detection layers. Suchan sampling electro-magnetic calorimeter could be applied for many experiments which needed both
high energy resolution and position / angle resolution. The performances have beed verified with thepositron beam at ELPH, Tohoku University.
1.1 Electro-magnetic calorimeter and experimental setup
The active absorber EM calorimeter has been introduced in order to improve both energy resolution
and position/angle resolution for photons. The calorimeter detector system is shown in figure 1.
This calorimeter consisting of active lead glass absorption layer and very fine granulated detection
scintillator layer [1]. The size of one layer of lead glass is 9 × 9 × 4 cm3 . It incorporates 9 lead glass

blocks of 3 × 3 × 4 cm3 in sizes. For each block aiming at improving the light collection, it is wrappedwith a reflector film, and light is not leaked to other blocks. Also, we installed 3 × 3 mm2 MPPC [2] forreading Cherenkov light in each block. It is a detector using 27 lead glass blocks in total and 27 MPPCs.
For the scintillator layer, we made 1 × 1 cm2 resolution by overlapping strip scintillators in the X

and Y directions. In each direction, nine strip scintillators of 18 × 1 × 0.3 cm3 were combined to create asize of 18 × 9 cm2 . Since they are placed in the X direction and the Y direction, the effective sensitivity

84

Fig.1. It becomes the DAQ system of this detector. The red line is the output of the trigger
detector. The black line is used to divide the trigger signal from the trigger detector.
Green line, clock distribution for synchronization of read. Yellow green line read 1 × 1
mm2 MPPC of scintillator. Purple line read of MPPC of 3 × 3 mm2 of segmented lead
glass and 12 × 12 mm2 of tail catcher.
region covers the same size as the lead glass absorption layer, 9 × 9 cm2 . The scintillator is wrappedwith a reflector film for each strip in order to improve light yield. Also, because of the uniformity of thescintillator response, the wave length shifted fiber is embedded in the groove. Light reading is performed
with one MPPC for each strip, and a total of 54 scintillators and MPPCs of 1 × 1 mm2 are used.

Tail Cather is made of a large single lead glass of 12 cm x 25 cm x 12 cm and uses one MPPC of 12

× 12 mm2 to measure the energy at the last detector. At the forefront, we installed the XY trigger andset it to trigger in the 1 cm x 1 cm area by taking the coincidence each scintillator.

All the signals from MPPCs in total 85 channels are read by three EASIROC modules which had
been developed for the MPPC read out through the ether-net [3].
1.2 Results
Here we show some results of the active absorber calorimeter tested at ELPH 2017.
The calibration result of the center channel of layer 2 together with tail catcher is shown in figure
2. Calibration was done by combining with a tail catcher, although calibration was difficult because theback leaked only with lead glass block alone. It is found that the energy dropped by the lead glass block
has a good correlation with the ADC count.
Further analysis is going on.
1.3 Conclusion
A sandwich type EM calorimeter has beed constructed and tested. A new feature for the detector
is using active absorber with segmentation. It became possible to perform calibration of each lead glass
block by beam.

85

Fig.2. Correspondence between energy and ADC in the center channel of the second layer oflead glass.

Acknowledgment
The authors thank the ELPH accelerator staff for providing the primary electron beam with goodquality. They are grateful to M. Miyabe for his technical support in preparation for the measurements.

References[1]

SF6W lead glass employed at TOPAZ , Kawabata et al.: NIM A 270 (1988) 11. et. al. NIM A
270(1988) 11.

[2]

MPPC trade mark of Hamamatsu Photonics CO.

[3]

Isamu Nakamura, N.Ishijima, K.Hanagaki, K.Yoshimura, Y.Nakai, K.Ueno, et al.:Nuclear Instruments and Methods in Physics Research A 787 (2015) 376-379.

86

ELPH Annual Report, Tohoku University (2017)

Influence of the Coulomb distortion on the measurement of
the proton radius
T. Tamae and T. Suda
Research Center for Electron Photon Science, Tohoku University, Sendai, 982-0826

Influence of the Coulomb distortion on the measurement of the root-mean square (rms) radius of
the proton is investigated through a phase-shift calculation. It is shown that the effect is severe evenfor the lightest nucleus, proton, and disturbs obtaining the rms radius of the proton from Taylor’s expansion. However it is found that this difficulty is removed almost completely by the so-called Feshbachcorrection. In addition, it is confirmed in this study that the cross section has no model dependence inthe energy region we are planning to perform the experiment, and depends on only the rms radius.

§ 1. Introduction

The discrepancy of the proton charge radius measured by electron scattering (R=0.88 fm) [1] andmuonic hydrogen (R=0.84 fm) [2–4] is known as “proton radius puzzle”. In most cases of electron scattering, the experimental data are analyzed in the framework of the plane-wave Born-approximation(PWBA), where no Coulomb distortion is considered. Rosenfelder [5] reanalyzed data measured at
Mainz [6–9] and Saskatoon [10] and pointed out that the Coulomb correction increases the proton radiusby about (0.008-0.013) fm, the opposite direction of the value from muonic atom. Energies of experiments
we are planning to explore is much lower than their energies and the influence from the Coulomb distortion is unknown. In this report we investigate the influence of the Coulomb distortion to our experiment.
we treat only the Coulomb scattering, and the magnetic part is separately considered.

§ 2. Electron Scattering

In the framework of the PWBA, the electron scattering cross section is represented bydσ
GE 2 + τ G2M−122 θ= σM frec+ 2τ GM tan
dΩ
1+τ
2

(1)

2

q
where τ = 4M
2 , m being the proton mass. σM and frec are the Mott cross section and a recoil factor,

respectively. The information of the structure for the proton is included in the charge and magnetic
form factors: GE , GM , and in the non-relativistic limit the charge form factor is obtained by the Fouriertransformation of the charge distribution ρ(r) asr.
GE (q) = ρ(r)eir·qd

(2)

87
As a guide for the following discussion, the charge form factors calculated by the Fourier trnansformationof the charge density with different proton sizes (rms) are shown in Fig. 1; the difference is a little lessthan 0.1% at q 2 =0.3 fm−2 for a difference of 0.1 fm of the proton size. At the limit of q = 0, the form
factor can be Taylor’s expansion as
GC = 1 −1  2 21  4 4r q +r q − ··· .
6
120

(3)

However the cross section is not represented by the simple formula of Eq. (1), if the Coulomb distortionis large.
1.01

rms radius: 0.82fm
rms radius: 0.84fm
rms radius: 0.86fm
rms radius: 0.88fm
rms radius: 0.90fm

Form Factor

1

0.99

0.98

0.97

0.96

Fig.1.

0

0.05

0.1

q

2

0.15

-2

(fm )

0.2

0.25

0.3

Form factors calculated by the Fourier transformation of the charge density with different
rms radius.

§ 3. Coulomb distortion

In this section, the cross section of the Coulomb scattering including the Coulomb distortion is

calculated. Usually the cross section affected by the Coulomb distortion is calculated in the phase-shift
analysis [11] using programs such as DREPHA [12] and MEFCAL [13] ; they were partly revised, which
is described in Appendix. If the effect from the Coulomb distortion is small, the charge form factor dσ 
asdefined from the cross section obtained in the phase-shift analysis dΩ
P SA dσ 
2

|GC (
q )| P SA =

dΩ

P SA

−1
σM frec(4)

may be in agreement with that from Eq. (2). In this situation, the form factors obtained with different
electron energies are expected to scale in the momentum transfer. Figure 2 shows the form factor with
the Coulomb distortion calculated using Eq. (4) for rms=0.88 fm; the results calculated by DREPHA and88
MEFCAL agree in an order of 10−4 in our energy region. It is obvious that the form factors obtained for
different electron energies do not scale and the derivative at low momentum transfers changes. It showsthat the proton size cannot be derived using a Taylor’s expansion of the form factor. It should be notedthat the form factor exceeds one at low momentum transfers; it is completely different from the form
factor obtained by the Fourier transformation of the charge distribution.
1.01

PSA: 20MeV
PSA: 30MeV
PSA: 40MeV
PSA: 50MeV
PSA: 60MeV
FourierForm Factor

1

0.99

0.98

0.97

0.96

Fig.2.

0

0.05

0.1

q

2

0.15

-2

(fm )

0.2

0.25

0.3

Form factors calculated by the phase-shift analysis (PSA) at θ=30◦ ∼ 150◦ and that obtained by the Fourier transformation of the charge density (Fourier) for rms=0.88 fm.
The form factors (PSA) calculated with different electron energies do not scale and are
different from the result of the Fourier transformation.

§ 4. Feshbach correction

The Mott cross section is derived from the lowest order Born approximation of the phase shift

analysis [14, 15]. Feshbach et al. [16, 17] obtained a correction factor from the second-order Born
approximation; it is represented as a simple form:Zαπ sin θ2 − sin2 θ2
fF eshbach = 1 +cos2 θ2Equation (4) is rewritten with the Feshbach correction as dσ 
2

|GC (
q )| F eshbach =

dΩ

P SA

−1
σM frecfF eshbach

.

(5)

(6)

The form factor calculated using Eq. (6) with a proton size of 0.88 fm is compared to the PWBA in
Fig. 3. Results calculated at different electron energies lies on a line, and the difference to the PWBA
is small; the rms radius obtained by fitting with a Taylor’s series is 0.882 fm. The result shows that
the Coulomb distortion can be mostly removed using the Feshbach correction. In order to confirm it

89
1.01

Feshbach: 20MeV
Feshbach: 30MeV
Feshbach: 40MeV
Feshbach: 50MeV
Feshbach: 60MeV
FourierForm Factor

1

0.99

0.98

0.97

0.96

Fig.3.

0

0.05

0.1

0.15

q2 (fm-2)

0.2

0.25

0.3

Form factors calculated with the Feshbach correction for rms=0.88 fm. The results fordifferent electron energies align on a lower line close to the line of the Fourier transformation.

numerically, the cross section for the point charge was calculated in the phase-shift calculation. The−1
fF eshbach agree the results of the phase-shift calculation in the order of 10−4 .
values of σM frec

§ 5. Model Dependence

Calculations in the previous section were performed for a dipole form factor (exponential-typecharge distribution). Although it is traditionally used for the proton, the charge distribution has acusp at the origin. Kelly [18] showed the gaussian-like distribution is better to describe experimental
data obtained at JLab. The charge distributions of an exponential-type and a gaussian with a same rms
radius (0.88 fm) are shown in Fig. 4. The form factors with Feshbach correction calculated using these
distributions at an electron energy of 50 MeV are compared in Fig. 5. The difference is very small for
low momentum transfers we are planning for experiments, and the cross section is determined by only
the rms radius; the difference becomes clearer at higher momentum transfers than 1fm−1 as Sick andTrautmann [19] pointed out.

§ 6. Results

Influence of the Coulomb distortion on the measurement of the proton size were investigated. It

was found that the influence was not negligible even for the proton; it is impossible to obtain the proton
size by Taylor’s expansion of the form factor under a simple PWBA scheme. However, the Feshbachcorrection reduces the influence dramatically, and we found that the proton size can be obtained with

90
sufficient accuracy. We compared the form factors for different charge distribution with same rms radius:
an exponential-type and a gaussian. Although the charge distributions are much different, the two form
3

dipolegaussian

3

Charge density (1/fm )

2.5

2

1.5

1

0.5

0

Fig.4.

0

0.5

1

1.5

r (fm)

2

Charge distribution of dipole form factor (exponential) and a gaussian. rms=0.88 fm

1.01

dipole:with Feshbach correction,
gaussian:with Feshbach correction,
Fourier: dipole
Fourier: gaussianForm Factor

1

0.99

0.98

0.97

0.96

Fig.5.

0

0.05

0.1

q

2

-2

0.15

(fm )

0.2

0.25

Form factors for different charge distribution with the Feshbach correction: an exponential (dipole form factor) and a gaussian. Ee =50 MeV, rms=0.88 fm

91factors are hard to be distinguished from each other at q 2 ≤ 0.3 fm−2 . As a result, we can conclude

that the rms radius of the proton can be obtained without the influence of the Coulomb distortion anddifference of the charge distribution. However, It should be noted that the result is true only for the
Coulomb part. The contribution of magnetic scattering is not negligible at backward angles: about 70%of the Coulomb part at Ee = 60 MeV and θe = 150◦ , for example. In addition, the Feshbach correction

does not insure the usability of the Rosenbluth separation. The Rosenbluth separation is useful onlyin the case where the Feshbach correction can remove the contribution of the Coulomb distortion onmagnetic scattering too. If not, the contribution of the magnetic part must be separately subtracted
from the measured cross section at first. This problem will be discussed in future.

Appendix
A. Phase-shift Analysis
In this section, the phase-shift calculation of electron scattering is briefly reviewed [11]. The differential cross section of electron scattering is given using a scattering amplitude f (θ) as follows:


dσ
1
1
2
2
= | f (θ) | 1 + tan2 θ = | f (θ) | sec2 θ.
(A1 )
dΩ
2
2
The amplitude is given using Legendre functions and phase-shifts ηj as



1 
1 
f (θ) =
exp 2iηj j +Pj− 1 (cos θ) + Pj+ 1 (cos θ) .
2
2
2ik
2

(A2 )

However, the amplitude does not converge because of the long-range nature of the Coulomb field. So theamplitude is divided into two parts as(A3 )f (θ) = fc (θ) + (f (θ) − fc (θ))

where fc (θ) is the Coulomb scattering amplitude, and f (θ) − fc (θ) converges; the treatment of fc (θ),

which does not converge, is described later. The Dirac equation is written by decomposing into partial
waves characterized by the total angular momentum j,
j+ 12
dGj
dx −
x Gj + (1 − v(x))Fj = 0,
j+ 12
dFj
dx +
x Fj − (1 − v(x))Gj = 0,

(A4 )where x = kr,Ev(x) = V (r)/E, k = h̄c. Individual asymptotic partial waves have the form11
Gj (x) ∼ sin x + γ ln 2x − (j − )π + ηj
(A5 )
2
2
2

where γ = Zeh̄c . Wave functions outside the nucleus, which are known as Coulomb functions, are written
at a point x0 (= kr0 ) (the “fitting-on point”) as two pair of linearly independent functions
Gj (x0 ) = Cj Gj,R (x0 ) + Dj Gj,I (x0 ),(A6 )Fj (x0 ) = Cj Fj,R (x0 ) + Dj Fj,I (x0 ),where the subscript R(I) denotes a Coulomb function which is regular (irregular) at the origin. The
asymptotic forms of the Coulomb functions are known:
Gj,R (x) ∼ sin[x + γ ln 2x − 21 (j − 21 )π + ηjc ],Gj,I (x) ∼ sin[x + γ ln 2x − 21 (j − 21 )π + ηjc ].


(A7 )

92
By comparing Eqs. (A5) and (A7) using Eq. (A6), we obtain
 

 

sin ηjc − ηjc
Dj sin ηjc − ηjc


,

 =

tan ηj − ηjc =
c

Cj
c
Cj + Dj cos ηjc − ηjc
Dj + cos ηj − ηj

(A8 )

where

Cj
Gj (x0 )FjI (x0 ) − Fj (x0 )GjI (x0 ).
=Dj
Fj (x0 )GjR (x0 ) − Gj FjR (x0 )(A9 )The cross section for an extended charge is calculating by inserting ηj obtauned here into Eq. (A2), andthat for a point charge can be obtained by putting ηj = ηjc . The Coulomb phase-shifts are calculated by
1 − i tan π(j + 21 − ρj ) coth πγ

1 exp −iπ j +exp i(ηj − ηj ) = − ρj1 − i tan π(j + 1 − ρj ) coth πγ 
2
2
 

ρj − iγ Γ (ρj − iγ)1
exp 2iηj c =
exp
iπ
j
+
−
ρ
.
j
2
j + 12 Γ (ρj + iγ)
cwhere ρj =c

j + 12

2

− γ2,

γ =

Ze2
h̄c .



(A10 ),(A11 )In the case where the nucleus has an extended charge
C

distribution, we solve the Dirac equation and obtain Djj by Eq. (A9); the procedure is described inAppendix B. As mentioned above the Coulomb scattering amplitude fc does not converge. Yennie et al.
mmultiplied fc by a function, which vanishes at θ=0, (1 − cos θ) ; the new amplitudem

fc (m) = (1 − cos θ) fc =1  (m)(Pl (cos θ))al
2ik(A12 )

rapidly converges and the Legendre polynomials are obtained. The final scattering amplitude is calculated byf (θ) =

fc (m) (θ)
m + (f (θ) − fc (θ)) ;(1 − cos θ)(A13 )

it converges except the very close angles near θ=0. The choice of m=3 is recommended in Yennie’s paper,
but m=4 is used in the original DREPHA program. We found m=2 is preferable in order to reduce anoscillation at forward angles.

B. Solving Dirac Equation
We solve the Dirac equation step-by-step fromthe origin
 to the fitting-on radius like a Runge-Kutta

method, but with higher accuracy [20]. Let yn = Fj be a radial wave functions at xn and yn+1
Gjnat xn+1 = xn + h. The wave functions and the Coulomb potential are expanded into Taylor’s series, then
1
1
1
1
1
yn+1 = yn + hyn  + h2 2!
yn  + h3 3!
yn  + h4 4!
yn (4) + h5 5!
yn (5) + h6 6!
yn (6)
1
1+h7 7!
yn (7) + h8 8!
yn (8) + · · ·

.

(B1 )

93
By differentiation and multiplication of h on eq. (B1), we get
1+ h3 2!
yn 

hyn  + h2 yn hyn+1  =h2 yn h2 yn+1  =1
1+h7 6!
yn (7) + h8 7!
yn (8) + · · ·1
1
1+ h4 2!
yn (4) + h5 3!
yn (5) + h6 4!
yn (6)+ h3 yn 11
yn (7) + h8 6!
yn (8) + · · ·+h7 5!

+ h4 yn (4)h3 yn h3 yn+1  =

11
1+ h4 3!
yn (4) + h5 4!
yn (5) + h6 5!
yn (6)

1+ h5 2!
yn (5)

1+ h6 3!
yn (6)

.

(B2 )

1
1
+h7 4!
yn (7) + h8 5!
yn (8) + · · ·h4 yn (4)h4 yn+1 (4) =+ h5 yn (5)1+ h6 2!
yn (6)

11+h7 3!
yn (7) + h8 4!
yn (8) + · · ·From Eqs. (B1) and (B2) after multiplying appropriate factors ai , we can make coefficients of h5 to h8 in
the right side to be zero; the error is an order of h9 as a result. The coefficients ai are derived by solving
equations


1
4!
1
5!
1
6!
1
7!

1
3!
1
4!
1
5!
1
6!

1
2!
1
3!
1
4!
1
5!

1







a
 1     a2  

=

 
  a3  

 
a4


 
a1
− 21


 

  3  a2   28.
=The solution is 

 
1 
 a3   − 84



 
1
a4
1680
Finally we get








1
2!
1
3!
1
4!

1
− 5!
1
− 6!
1
− 7!
1
− 8!






.




3
1
1
h2 yn+1  − 84
h3 yn+1  + 1680
h4 yn+1 (4)yn+1 − 12 hyn+1  + 28

3
1
1
= yn + 21 hyn  + 28
h2 yn  + 84
h3 yn  + 1680
h4 yn (4) + O(h9 )

then

(B3 )

,


−1
3
1
1
yn+1 = 1 − 21 hAn+1 + 28
h2 Bn+1 − 84
h3 Cn+1 + 1680
h4 Dn+13
1
1
h2 yn  + 84
h3 yn  + 1680
h4 yn (4) + O(h9 )yn + 21 hyn  + 28

(B4 )

(B5 )

This equation includes derivatives of yn+1 up to forth order; they can be represented using the Diracequation;

where



y  n+1 = L− xn+1− (1 − vn+1 )1 − vn+1
L

xn+1




Fj
Gj



 ≡ An+1 yn+1 ,

E
Vn+1
, k=
.
E
h̄c
Higher order derivatives are obtained successively, for example,
xn+1 = krn+1 ,vn+1 =

y  n+1 ≡ Bn+1 yn+1 = A n+1 yn+1 + An+1 y  n+1 = A n+1 + A2 n+1 yn+1 .

(B6 )

(B7 )

(B8 )

Using obtained matrices, yn+1 can be calculated from yn with Eq. (B5). In DREPHA, a procedure witha lower order of accuracy is used at x ≤ 1, which is shown in Yennie’s paper, and Eq. (B5) at x > 1. The
procedure using Eq. (B5) through a whole region makes no difference.

94
B-1. Initial values at the origin
If initial values of the wave function at the origin (x=0) is fixed, the wave function can be calculatedusing Eq. (B5) throughout a whole region. Around the origin, G(x), F (x), and v(x) are expanded into
Taylor’s series:
1
1
1
G (0)x2 + 3!
G (0)x3 + 4!
G(4) (0)x4 + · · ·G(x) = G(0) + G (0)x + 2!

1
1
1
F (x) = F (0) + F  (0)x + 2!
F  (0)x2 + 3!
F  (0)x3 + 4!
F (4) (0)x4 + · · ·

(B9 )

1 
1 
v (0)x2 + 3!
v (0)x3 + · · ·v(x) = v(0) + v  (0)x + 2!

By using these expressions in the Dirac equation, we obtain

and

1
1
G (0)x2 + 3!
G(4) (0)x3 + · · ·G (0) + G (0)x + 2!


1
1
1



2
(4)
3
−L G(0)
+
G
(0)
+
G
(0)x
+
G
(0)x
+
G
(0)x
+
·
·
·
x
2!
3!
4!


1 
1 
v (0)x2 − 3!
v (0)x3 + · · ·+ 1 − v(0) − v  (0)x − 2!


1
1
1
F  (0)x2 + 3!
F  (0)x3 + 4!
F (4) (0)x4 + · · · = 0
F (0) + F  (0)x + 2!
1
1
F  (0)x2 + 3!
F (4) (0)x3 + · · ·F  (0) + F  (0)x + 2!


1
1
1
F  (0)x + 3!
F  (0)x2 + 4!
F (4) (0)x3 + · · ·+L F x(0) + F  (0) + 2!


1 
1 
v (0)x2 + 3!
v (0)x3 + · · ·+ −1 + v(0) + v  (0)x + 2!


1
1
1
G (0)x2 + 3!
G (0)x3 + 4!
G(4) (0)x4 + · · · = 0
G(0) + G (0)x + 2!

(B10 )(B11 )

Applying an undetermined coefficient method on individual orders of x terms, we can fix the coefficients
G(0), F (0), G (0), F  (0), · · · . The first non-zero coefficient is G(L) (0). As the solution is unfixed (arbi-

trary), we can put it as

1 (L)
G (0)xL = 1.
L!

(B12 )

Coefficients of higher derivatives can be obtained successively, and finally we can calculate initial values
around the origin using
11
1
G(L) (0)xL + (L+1)!
G(L+1) (0)xL+1 + (L+2)!
G(L+2) (0)xL+2
G(x) = L!
1
1+ (L+3)!
G(L+3) (0)xL+3 + (L+4)!
G(L+4) (0)xL+4(B13 )and1
1
F (L+1) (0)xL+1 + (L+2)!
F (L+2) (0)xL+2
F (x) = (L+1)!
1
1
F (L+3) (0)xL+3 + (L+4)!
F (L+4) (0)xL+4 .
+ (L+3)!

(B14 )It should be noted that the phase-shift is not affected by the choice of G(L) (0) because it is determinedfrom the ratio of G and F .
B-2. Coulomb potential
The Coulomb potential is calculated by the expression
 x

 ∞
Ze2 1
Ze2
2
−v(x) =
ρ(x )4πx dx +ρ(x )4πx dx
h̄c x
h̄c x
0

(B15 )

95
where the charge density ρ is normalized as ∞2
ρ(x )4πx dx = 1.

(B16 )

0

In the program DREPHA, the value of v(x) and its Taylor’s series at the origin is numerically calculated.
In MEFCAL, on the contrary, they are calculated directly from Fourier-Bessel parameters of the charge
distribution, where the charge distribution is represented as
ρ(r) =

sin(iπr/R)
,
iπr/R

ai

i

(B17 )

where R is the cut-off radius. Then,−v(r) =

Z 2 e2
4Ze2 R3 1  ai.
sin(iπr/R)+
π 2 h̄c ri3h̄cR(B18 )i

The potential at the origin and their derivatives, which are used in Eqs. (B10) and (B11), are ai sin(iπr/R)
 ai
2 R
π
π 1
4Ze2 R3



+
−
ρ(r
)4πr
dr
=
cos(iπr/R)−v(0) = Ze
h̄c
Rr
iπr/R
R r
0
π 2 h̄c
i2
i2
2

R
= 8Ze
πh̄c

i



2

k odd

−v  (0) = 0,2−v  (0) = − 4πZeh̄c−v  (0) = 0.



i

ak
,
k2

ai ,

i

(B19 )(B20 )

B-2-1. Exponential-type charge distribution (Dipole form factor)
In the case of the proton, as the dipole form factor is used as a standard form factor, it was added in
the programs. The charge distribution is given as
ρ(r) =a3
exp(−ar).
8π(B21 )As the exponential-type distribution has a cusp at the origin, its Fourier-Bessel expansion does notconverge. Instead the potential and its Taylor’s series at the origin can be obtained analytically as


Ze2
1
a
(B22 )−v(r) = −{exp(−ar) − 1} +exp(−ar)
h̄c
r
2
2

a
−v(0) = Ze
2h̄c ,−v  (0) = 0,23a−v  (0) = − Ze6h̄c ,
2(B23 )

4a−v  (0) = Ze
4h̄c .

These formulae were added in MEFCAL.
Acknowledgments
We would like to thank Professors J. Friedrich, L. Lapikás, and H. Blok for their useful discussions.
This work was supported by Grants-in-Aid for Scientific Reserch ( JP16H06340).

96

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for example, J.C. Bernauer et al., Phys. Rev. C 90 (2014) 015206 and its references.

[2]

R. Pohl et al., Nature 466 (2010) 213.

[3]

R. Pohl et al., Science 353 (2016) 669.

[4]

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[5]

R. Rosenfelder, Phys. Lett. 27 (2000) 381.

[6]

G.G. Simon et al., Nucl. Phys. A 333 (1980) 38.

[7]

G.G. Simon et al., Nucl. Phys. A 364 (1981) 285.

[8]

F. Borkowski et al., Nucl. Phys. A 222 (1974) 269.

[9]

F. Borkowski et al., Nucl. Phys. B 93 (1975) 461.

[10] J.J. Murphy, Y.M. Shin and D.M. Skopik, Phys. Rev. C 9 (1974) 2125.
[11] D.R. Yennie, D.G. Ravenhall, and R.N. Wilson, Phys. Rev. 95 (1954) 500.
[12] B. Dreher, DREPHA: a phase-shift calculation code for electron scattering developed at Mainz,
communicated by J. Friedrich.
[13] MEFCAL: a phase-shift calculation code for electron scattering written in NIKHEF, communicatedby L. Lapikás and H. Blok.
[14] N.F. Mott, Roy. Soc. A124 (1929) 425.
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[16] W.A. McKinley Jr. and H.Feshbach, Phys. Rev. 74 (1948) 1759.
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[18] J.J. Kelly, Phys. Rev. C66 (2002) 065203.
[19] I. Sick and D. Trautmann, Phys. Rev. C95 (2017) 012501(R).
[20] W.E. Milne, Numerical Solution of Differential Equations (Dover Publications, Inc., New York)(1953) .

ELPH Annual Report, Tohoku University (2017)

97

Light meson photoproduction off the proton at the SPring-8
BGOegg experiment
Norihito Muramatsu1 , Jung Keun Ahn13 , Wen-Chen Chang4 , Jia-Ye Chen5 ,Schin Daté3 , Toshiyuki Gogami2 , Hirotomo Hamano2 , Toshikazu Hashimoto6 ,Qing Hua He1 , Kenneth Hicks7 , Toshihiko Hiraiwa2 , Yuki Honda1 ,Tomoaki Hotta2 , Yosuke Inoue1 , Takatsugu Ishikawa1 , Igal Jaegle8 ,Ja Min Jo13 , Yuuto Kasamatsu2 , Hitoshi Katsuragawa2 , Satoshi Kido1 ,Yukiyoshi Kon2 , Shinichi Masumoto9 , Yuji Matsumura1 , Katsumasa Miki12 ,Manabu Miyabe1 , Keigo Mizutani6 , Taiki Nakamura12 , Takashi Nakano2 ,Masayuki Niiyama6 , Yuki Nozawa6 , Yuji Ohashi3 , Haruo Ohkuma3 ,Hiroaki Ohnishi1 , Takeshi Ohta2 , Masaya Oka2 , Kyoichiro Ozawa11 ,Yuta Sada2 , Mizuki Sasagawa1 , Takuya Shibukawa9 , Hajime Shimizu1 ,Rintaro Shirai1 , Ken’ichiro Shiraishi1 , Yorihito Sugaya2 ,Mizuki Sumihama12 , Shinsuke Suzuki3 , Shintaro Tanaka2 ,Atsushi Tokiyasu1 , Natsuki Tomida2 , Nam Tran2 , Yusuke Tsuchikawa1 ,Tadayuki Ueda1 , Hirohito Yamazaki1 , Ryuji Yamazaki1 , Yuka Yanai2 ,Tetsuhiko Yorita2 , Chihiro Yoshida1 , and Masaru Yosoi2
1

Research Center for Electron Photon Science, Tohoku University, Sendai, Miyagi 982-0826, Japan
2
3

Research Center for Nuclear Physics, Osaka University, Ibaraki, Osaka 567-0047, Japan

Japan Synchrotron Radiation Research Institute (SPring-8), Sayo, Hyogo 679-5198, Japan
4
5

6
7

Institute of Physics, Academia Sinica, Taipei 11529, Taiwan

National Synchrotron Radiation Research Center, Hsinchu 30076, Taiwan
Department of Physics, Kyoto University, Kyoto 606-8502, Japan

Department of Physics and Astronomy, Ohio University, Athens, OH 45701, USA
89University of Hawaii at Manoa, Honolulu, HI 96822, USA

Department of Physics, University of Tokyo, Tokyo 113-0033, Japan
10

11

RIKEN Nishina Center, Wako, Saitama 351-0198, Japan

Institute of Particle and Nuclear Studies, High Energy Accelerator Research Organization (KEK),
Tsukuba, Ibaraki 305-0801, Japan
12
13

Department of Education, Gifu University, Gifu 501-1193, Japan

Department of Physics, Korea University, Seoul 02841, Republic of Korea

The photoproduction of a light meson such as π 0 , η, and ω was studied by using the data collectedwith a liquid hydrogen (LH2 ) target at the SPring-8 BGOegg experiment. The differential cross sections
and photon beam asymmetries of these reactions were measured to examine baryon resonances for understanding the hadron structure at the quark level. By using the LEPS2 photon beam (1.3–2.4 GeV),
we can explore the center-of-mass (CM) energy range above the third resonance region, where excitedstates appear with wide widths. The linearly polarized photon beam, available at the SPring-8/LEPS2

98beamline, has advantage to decompose those overlapped states by measuring the interfered amplitudes
through the photon beam asymmetries.
The photoproduction of η and ω, whose isospin is zero, couples only to nucleon resonances (N ∗ s)
thanks to the isospin conservation in the s-channel. Particularly, the η photoproduction is a good probe
for the N ∗ s including ss̄ content. On the other hand, the π 0 meson is photoproduced via both N ∗ s and∆∗ s. Nevertheless, the contributing baryon resonances are being understood well because this reaction
has been intensively investigated with high statistics at many experiments. The analysis of the π 0
photoproduction at the BGOegg experiment mainly aims the confirmation of the luminosity estimationand the analysis methods for other reaction modes. For all of the above photoproduction processes, thephoton beam asymmetries in the energy region greater than Eγ ∼ 2 GeV are very scarce and desired as
new experimental information. The BGOegg experiment has obtained such new data as described below.
The individual light mesons were detected at the BGOegg electromagnetic calorimeter to reconstruct the invariant mass. The π 0 and η mesons were identified in the 2γ decay mode, while the ω
meson was detected via ω → π 0 γ → 3γ decays. The BGOegg calorimeter is the “egg”-shaped assembly of 1,320 BGO crystals, covering the polar angle range from 24◦ to 144◦ . The proton recoiled in themeson photoproduction was detected at the planar drift chamber (DC) or the BGOegg calorimeter withthe charge identification by the inner plastic scintillators (IPS). The DC was installed at the forward
acceptance hole of the BGOegg calorimeter, corresponding to the polar angles less than 21◦ . The experimental data was collected in the latter half of FY2014 (the 2014B cycle) by irradiating a few MHz photon
beam onto the 54 mm-thick LH2 target at the SPring-8 LEPS2 beamline. The energy and intensity ofthe photon beam were measured at the tagging counter for the recoil electrons from backward Compton
scattering. The integrated photon beam counts have reached 3.6 × 1012 in 2014B.
The signal event sample was selected based on the kinematic fit with the constraints by the 4momentum conservation and the π 0 and η masses. The ω mass was not used for a restricting condition
because of its natural width, but the π 0 mass among the decay products was constrained to the PDG
value. After requiring the χ2 probability of the kinematic fit to be greater than 1% or 2%, the remaining
sample entries for the π 0 , η, and ω photoproduction become ∼ 650K, ∼ 56K, and ∼ 75K events,
respectively. Background contamination is negligibly small for the π 0 and η photoproduction, while theγp → π 0 π 0 p events with a missing γ is broadly distributed under the signal peak in the π 0 γ invariant
mass distribution for the ω photoproduction. The ω signal counts were finally estimated to be ∼ 37K
events by fitting a Voigt function with a background template shape generated by a Monte Carlo (MC)simulation.
The differential cross sections dσ/dΩ were measured in the photon energy bins of each several
tens MeV and the meson polar angle bins (cos θ at the CM frame) of each 0.1. The photoproduction
yields at the individual kinematical bins were divided by the acceptance factors evaluated using the
GEANT4-based MC simulations and by the luminosities calculated from the LH2 target thickness andthe number of tagging counter triggers with the 150 m beamline transmission of about 77%. Figures 1
and 2 show the measured differential cross sections for the π 0 photoproduction. The preliminary result

99

Fig.1.

Differential cross section for the π 0 photoproduction at Eγ < 1.9 GeV. The BGOegg
result is shown by the closed circles, while the squares, open circles, triangles, diamonds,
and crosses indicate the measurements by CLAS [1], CBELSA 2005 [2], CBELSA 2011[3], GRAAL [4], and LEPS [5]. The histogram represents the systematic errors of the
BGOegg measurement.

Fig.2.

Differential cross section for the π 0 photoproduction at Eγ ≥ 1.9 GeV. The meanings ofthe markers and the histogram are the same as those in Fig. 1.

100

Fig.3.

Differential cross section for the ω photoproduction. The BGOegg result is shown by theclosed circles, while the squares, open circles, crosses, and triangles indicate the measurements by CLAS [9], CBELSA [10], LEPS [11], and LEPS-TPC [12]. The histogram
represents the systematic errors of the BGOegg measurement.

Fig.4.

Photon beam asymmetry Σ for the π 0 photoproduction. The BGOegg result (closed circles)
is compared with the existing PWA model calculations. The red, blue, and green curves
are obtained by the Bonn-Gatchina [6], SAID [7], and ANL-Osaka [8] models, respectively.

101of the BGOegg measurement is consistent with the CLAS, GRAAL, and LEPS results, while there are
discrepancies from the CBELSA results at low energies and backward angles. The differential crosssections for the ω photoproduction are also measured as shown in Fig. 3, indicating the values close toother experimental results.
The photon beam asymmetry Σ was measured as the yield modulation depending on the azimuthal
angle difference between the reaction plane and the photon beam polarization vector. Figures 4 and 5
show the BGOegg results of beam asymmetry measurements for the π 0 and ω photoproduction, respectively. Solid lines indicate the theoretical model calculations by partial wave analyses (PWA). The PWA
model calculations generally reproduce the measured beam asymmetries at the lower energies because
they are fitted to the existing experimental data. However, the consistencies become worse at the highest energy bins, where the beam asymmetry data is lacking. The new measurements by the BGOegg
experiment must provide strong constraints on the decomposition possibilities of N ∗ s and ∆∗ s. New fits
by the PWA models are now in progress.

Fig.5.

Photon beam asymmetry Σ for the ω photoproduction. The BGOegg result (closed circles) is compared with the existing PWA model calculation by Bonn-Gatchina group (solidlines) [13].

102

References[1]

M. Dugger et al., Phys. Rev. C 76, 025211 (2007).

[2]

O. Bartholomy et al., Phys. Rev. Lett. 94, 012003 (2005).

[3]

V. Crede et al., Phys. Rev. C 84, 055203 (2011).

[4]

O. Bartalini et al., Euro. Phys. J. A26, 399 (2005).

[5]

M. Sumihama et al., Phys. Lett. B 657, 32 (2007).

[6]

https://pwa.hiskp.uni-bonn.de/BG2014 02 obs int.htm.

[7]

http://gwdac.phys.gwu.edu/analysis/pr analysis.html.

[8]

T. Sato, Private communication.

[9]

M. Williams et al., Phys. Rev. C 80, 065208 (2009).

[10] F. Dietz et al., Euro. Phys. J. A51, 6 (2015).
[11] M. Sumihama et al., Phys. Rev. C 80, 052201R (2009).
[12] Y. Morino et al., Prog. Theor. Exp. Phys. 2015, 013D01.
[13] A. Sarantsev and V. Nikonov, Private communication; P. Roy et al., Phys. Rev. C 97, 055202 (2018).

ELPH Annual Report, Tohoku University (2017)103

A trial to measure a spectral function of η ′ mesons
H. Shimizu1 , Y. Matsumura1 , J. K. Ahn2 , W. C. Chang3 , J. Y. Chen4 , S. Daté5 ,T. Gogami6 , H. Hamano6 , T. Hashimoto7 , Q. He8 , T. Hiraiwa6 , Y. Honda1 ,T. Hotta6 , T. Ishikawa1 , J. M. Jo2 , Y. Kasamatsu6 , H. Katsuragawa6 , Y. Kon6 ,S. Masumoto9 , K. Miki10 , M. Miyabe1 , K. Mizutani7 , N. Muramatsu1 ,T. Nakamura10 , T. Nakano6 , M. Niiyama7 , Y. Nozawa7 , Y. Ohashi5 ,H. Ohnishi1 , T. Ohta6 , M. Oka6 , K. Ozawa11 , C. Rangacharyulu12 , Y. Sada6 ,T. Shibukawa9 , R. Shirai1 , Y. Sugaya6 , M. Sumihama10 , S. Suzuki5 ,S. Tanaka6 , Y. Taniguchi1 , A. Tokiyasu1 , N. Tomida6 , N. Tran6 ,Y. Tsuchikawa13 , T. Ueda1 , H. Yamazaki11 , R. Yamazaki1 , T. Yorita6 ,C. Yoshida1 , and M. Yosoi61Research Center for Electron Photon Science, Tohoku University, Sendai, 982-0826
2

Department of Physics, Korea University, Seoul 02841
3

45

National Synchrotron Radiation Research Center, Hsinchu 30076

Japan Synchrotron Radiation Research Institute (SPring-8), Hyogo 679-5198
6

Research Center for Nuclear Physics, Osaka University, Osaka 567-0047
78Institute of Physics, Academia Sinica, Taipei 11529

Department of Physics, Kyoto University, Kyoto 606-8502

Department of Nuclear Science & Engineering, Nanjing University, Nanjing 210016
9Department of Physics, University of Tokyo, Tokyo 113-0033

10
11
12

Department of Education, Gifu University, Gifu 501-1193

Institute of Particle and Nuclear Studies, KEK, Tsukuba 305-0801

Department of Physics, University of Saskatchewan, Saskatoon S7N 5E2
13Department of Physics, Nagoya University, Nagoya 464-8602

An attempt has been made at SPring-8/LEPS2 to measure the spectral function of η ′ mesons propagating in the nuclear medium, where chiral symmetry in flavor space is expected to be partially restored.
The spectral function of η ′ may provide essential information on how spontaneous symmetry breaking
takes place in connection with axial U (1) anomaly and whether an η ′ -nucleus bound state exists or not.
For this purpose, an electromagnetic calorimeter, BGOegg, is employed to detect η ′ → γγ decay inside a

nucleus with a small but detectable probability. The η ′ → π 0 π 0 η decay process may provide another pos-sibility to find a visible effect of chiral symmetry restoration in the nucleus. BGOegg consisting of 1320
BGO crystals exhibits an excellent calorimeter performance both in the energy and mass resolutions.

§ 1. Introduction

Incorporating quantum electro-weak dynamics and quantum chromodynamics (QCD), the standard

model describes nature very well. However, Two big questions remain unsolved in the QCD sector, on

104
the confinement of quarks and mass generation of hadrons, which have to be solved in the frameworkof the standard model. These questions arise from the non-perturbative regime of QCD, which is still
not well-understood because of a complicated situation brought about by the gauge boson gluon, which
carries color charges by itself.
In such a hard environment surrounding non-perturbative QCD, Nambu formulated a low energy
chiral effective theory [1] known as the Nambu–Jona-Lasinio (NJL) model that includes no gluon fields,
following his pioneering work on spontaneous symmetry breaking. The NJL model that respects chiralsymmetry in quark flavor space, originally in iso-spin space for the nucleon doublet, well explains how
the hadron mass is generated. It is now widely accepted way of understanding that chiral symmetry
is one of the most fundamental properties of QCD and is spontaneously broken in our real world due
to ⟨q̄q⟩ ≠ 0, the non-zero vacuum expectation value of quark-antiquark condensate. The ⟨q̄q⟩ value isthought to mainly determine the hadron mass. Surprisingly, the ⟨q̄q⟩ value accounts for about 99% of

the mass of ordinary matter surrounding us, according to many effective theories based on the Nambu
theory. (The contribution of Higgs fields to the mass generation of ordinary matter is merely the order of1%.) However, no clear experimental evidence has been found for this scenario, which has to be proved
experimentally in the framework of the standard model.

§ 2. Chiral symmetry and axial U (1) anomaly

Under SU (3) symmetry for three quark flavors,



 

m1
u
q1
0
0



 




 

m =  0 m2
=  q2  =  d  ,
0 



 

s
q3
0
0 m3

(m1 ≃ m2 ≃ m3 ),(1)

the q q̄ meson multiplets are classified into a singlet and an octet, 3 ⊗ 3̄ = 1 ⊕ 8, originally taking placealternatively. But there exists the flavor SU (3) symmetry-breaking interaction, which mixes the singlet

and octet states having the same quantum numbers I = Y = 0. It is, therefore, convenient to regard themeson multiplet as a nonet belonging to an irreducible representation of a U (3) group. In the low-lying
pseudoscalar meson multiplet, η(548) and η ′ (958) are the mixtures of the singlet η0 and the octet η8with η ′ mostly made up of η0 . The η ′ meson as a member of the nonet, however, cannot be associatedwith U (3) symmetry since the η ′ mass is considerably higher than the masses of the other members,
K ′ s, η, and π’s. This is the axial U (1) problem relating to the singlet η0 .
The simplest classical QCD Lagrangian for three quark flavors is given by
LQCD = ψ̄(iγ µ Dµ − m)ψ −1 a aµν
F F
,
4 µν

(2)

a
describing a physical system of free quarks ψ and gluons Aaµ included in the field strength tensors Fµν .

This Lagrangian originally satisfies U (3)L ⊗ U (3)R chiral symmetry, which decomposes into smaller
symmetry groups as

U (3)L ⊗ U (3)R ≃ U (1)V ⊗ U (1)A ⊗ SU (3)L ⊗ SU (3)RSU (3)L ⊗ SU (3)R ≃ SU (3)V ⊗ SU (3)A .

(3)
(4)

105
All Noether currents corresponding to the individual symmetries are conserved for classical fields in thechiral limit. But when we come to quantum fields, the singlet axial current, ψ̄γ µ γ5 ψ, caused by theaxial U (1) symmetry (U (1)A symmetry) is not conserved any more since the divergence of this current
is now given by∂µ (ψ̄γ µ γ5 ψ) = 2imj q̄j γ5 qj + 2NF

1 g 2 a aµν
F F̃
̸= 0,
8π 4π µν

(5)

where F̃ aµν is the dual tensor of F aµν . The first term on the right-hand side vanishes in the chiral limit,
while the second term is a non-zero quantity known as the charge density operator that originates fromthe quantum effect of gluon fields. The other currents remain conserved even for the quantum fields.
Thus the topological charge density operator gives rise to the axial U (1) anomaly.
The QCD Lagrangian (2) has now U (1)V ⊗ SU (3)L ⊗ SU (3)R symmetry in the chiral limit with bro-

ken axial U (1) symmetry. Then SU (3)L ⊗ SU (3)R chiral symmetry is spontaneously broken. To get theeffect of the axial U (1) anomaly into effective theories based on the NJL model, which keep possessing

axial U (1) symmetry, the Kobayashi-Maskawa-’t Hooft (KMT) six-quark interaction [2] is introduced tobreak axial U (1) symmetry. An extended NJL model importing the KMT interaction predicts a large inmedium mass reduction of the η ′ meson by about 150 MeV at the normal nuclear density [3]. According
to the prediction for three quark flavors, the η ′ mass goes down and gets degenerate with the η mass
when the nuclear density goes up if a density-independent coupling constant is employed for the KMTterm. Consequently a bound state of the η ′ and a nucleus might come about, depending on the strengthof the η ′ -nucleus potential, which shows an attractive force due to the in-medium η ′ mass reduction.
Although no exact predictions are given for the real and imaginary parts of the η ′ -nucleus optical potential, the logic described here might lead to an idea of axial U (1) symmetry restoration driven by chiralrestoration.
A simple question arises here. Does chiral symmetry restoration really affect axial U (1) symmetry?
The axial U (1) anomaly originates from the quantization of gluon fields. And the KMT term is introduced into effective theories just to break down axial U (1) symmetry. The relation between the topological charge of gluon fields and the KMT term is not straight forward. However, we may give an answer tothe question from the point of view of ”symmetry arguments [4].” The QCD Lagrangian for three quark
flavors has SU (3)L ⊗ SU (3)R chiral symmetry, which is basically equivalent to SU (3)V ⊗ SU (3)A sym-

metry and is, therefore, invariant under octet axial transformations generated by the octet axial charges
Qb5 corresponding to the SU (3)A symmetry. Then octet scalars S a in the q q̄ meson states transform as
θ5b [iQb5 , S a ] = −dabc θ5b P c −2 a
θ P0 ,
3 5(6)

being mixed with octet P c and singlet P0 pseudoscalars, where θ5b are transformation parameters anddabc denote the d-coefficients of anticommutation relations of SU (3) generators. As a consequence,
when the spontaneously broken chiral symmetry is restored, the octet S a scalars, the singlet η0 = P0
and octet η8 ∈ P c pseudoscalars must get degenerate in mass, irrespective of axial U (1) anomaly. Thisconsequence, however, does not necessarily mean axial U (1) symmetry restoration [4]. The σ(500) andf0 (980) would be mixtures of the singlet S0 and an octet S a scalar. The remaining octet scalars are three106
a0 (980)′ s and four κ(800)′ s [5] that are not well established.

§ 3. η ′ → γγ decay in the nuclear medium

We try to search for the effect of η ′ mass going down in the nuclear medium by measuring thespectral function defined as the imaginary part of the η ′ propagator in a nucleus. An appropriate decay
process taking place in the nucleus should be selected at first in this study to avoid undesirable distortion
effects from the residual nucleus. We focus on the η ′ → γγ process, which includes no strong interacting
particles in the final state and therefore may also be able to provide information on an η ′ −nucleus boundstate if it exists. The natural width of the η ′ meson is about 197 keV, which is too narrow, in general,
for whatever experiments detecting η ′ decay in a nucleus, unless η ′ is bounded. Assuming η ′ mesons
having a momentum of 400 MeV/c in free space, for example, we may observe the γγ decay events about
400 fm away from the η ′ created points with the branching ratio of 2.2% sinceβγτ0 ≃ 0.4

197 MeV · fm
= 400 fm,
197 keV(7)

where τ0 is the lifetime of the η ′ meson. The natural width of the η ′ meson Γ0 is given by the sum of all
the partial decay widths in free space,Γ0 (η ′ ) = Γγγ + Γ1 + Γ2 + · · · + Γππη = 197 keV,

(8)almost determined by the main decay channels, η ′ → ππη (65%) and η ′ → π + π − γ (29%). Each partial

width is determined by the invariant amplitude describing the decay process and the phase space volume
in the final state, being experimentally obtainable by measuring the total width and the branching ratio
to the process under consideration. The partial width of γγ decay Γγγ is then found to be 4.3 keV

corresponding to the known branching ratio of 2.2% to the γγ channel.
Using a nuclear target, we would have a hard time, therefore, finding the events decaying into γγ
inside the nucleus. But the decay events occurring within the nucleus are not absolutely undetectable.
The CBELSA/TAPS Collaboration recently provides the most relevant experimental result on the η ′ nucleus potential [6], the real part of which is found to be −(37 ± 10stat ± 10syst ) MeV, showing an

attractive force. The obtained potential also shows a small imaginary part of −(10 ± 2.5) MeV, whichcorresponds to the in-medium width of η ′ to be about 20 MeV at the normal nuclear density. Taking thisvalue for the total width ΓA of η ′ in the nuclear medium, we can estimate the rate of γγ decay inside tooutside the nucleus. We define here a decay length, L0 , corresponding to the total decay width Γ0 = 1/τ0
in free space for a fixed βγ ≈ 0.4 of η ′ ,L0 = βγτ0 ≃ 400 fm

for Γ0 ≃ 200 keV,(9)having another decay length, LA , corresponding to the total width ΓA = 1/τA in the nucleus,
LA = βγτA ≃ 4 fm

for ΓA ≃ 20 MeV,

(10)

where τA denotes the lifetime of η ′ in the nucleus. The fraction Rγγ (x < r) of η ′ → γγ decay inside thenucleus can be written by
Rγγ (x < r) =

Γγγ
ΓA

(

(
))
r
1 − exp −
,
LA

(11)

107
where r is the average distance from a η ′ created point to the boundary in the nucleus. The fraction
Rγγ (r < x) of γγ decay outside is then given by
)
(
Γγγ
r
.
exp −
Rγγ (r < x) =Γ0LAThus the rate of γγ decay inside to outside the nucleus is obtained as
[
(
)
]
Γ0
Rγγ (x < r)
r
=
exp
−1 ,
Rγγ (r < x)
ΓA
LA

(12)

(13)

which is independent of Γγγ . Provided that an average propagation length r of η ′ through the nucleus
is taken to be 2.7 fm, which is the same length of the carbon radius, and the total width ΓA of η ′ in the
nucleus to be 20 MeV, we have the rateRγγ (x < r)
≃ 1%
Rγγ (all)(14)for η ′ having a relative momentum of 400 MeV/c in the residual nucleus. This effect may be observed in
the spectral function of η ′ → γγ events. The rate is expected to go up if we use a heavier nucleus witha larger radius. In comparison, the similar estimation yields the rate of 6.8 × 10−3 for the case that the
total width of η ′ is unchanged in the nucleus.

Here is another decay process to be investigated to search for chiral restoration phenomena in
addition to the γγ decay channel. If the η ′ mass decreases by about 100 MeV in the nuclear medium,η ′ → π 0 π 0 η decay is strongly suppressed since the available momentum space becomes very limited forthis channel. This means the partial width of η ′ → π 0 π 0 η decay goes down and accordingly diminishes

the branching ratio to this channel. Thus we expect to haveΓ′ππη ≪ Γππη ,(15)where Γ′ππη and Γππη denote the partial decay widths in the nuclear medium and in free space, respectively. It does not matter to have strongly interacting hadrons in the final state in the measurement of
the branching ratio in this case. We measure the branching ratio to the π 0 π 0 η channel using a nuclear
target and a liquid hydrogen target to compare the results. Just the change of the branching ratio provides information on partial restoration of chiral symmetry, irrespective of distortion effects taking placeon the final-state hadrons in the nuclear medium.
It is useful to have better information on the fundamental properties of the η ′ meson in free spacein the study of η ′ in the nuclear medium. Precise measurements have recently been made at COSY
for the total width of η ′ [7] and the η ′ -nucleon scattering length [8], which may yield information on η ′scattering processes in the nuclear medium.

§ 4. BGOegg Experiments at SPring-8/LEPS2

A series of experiments has been conducted at the LEPS2 beamline [9] in SPring-8 to find the effectof partial restoration of chiral symmetry in the nuclear medium. A 2.4 GeV laser-electron-photon beam
is utilized with a typical intensity of 106 tagged photons/s. The common experimental layout for theseexperiments is illustrated in Fig. 1. An electromagnetic calorimeter, BGOegg, was installed as the main

108
detector assembly equipped with a cylindrical drift chamber (CDC) and an inner scintillator hodoscope.
Forward-going charged particles can be detected with a time-of -flight (TOF) hodoscope made of resistive

Resistive Plate
Chamber (RPC)

BGOeggTarget(LH2 , C)

Charge Veto
Counter

6.8 ｏ

21ｏ

2m(V) x 3.2m(H)

1.28m

21ｏ

Cylindrical
Drift Chamber (CDC)
Inner Plastic Scintillator (IPS)
0

6.8 ｏ

E949 solenoid
magnetDrift Chamber (DC)
1.6

12.5 zm

Fig.1. Plan view of the common experimental setup for BGOegg experiments.
plate chambers (RPC) placed 12.5 m downstream of the target. The TOF resolution is found to be 80
ps, which corresponds to the energy resolution of ∼20 MeV for 2 GeV/c protons. A big solenoid magnet

shown in Fig. 1 is not used in the current BGOegg experiments.

The BGOegg calorimeter is an egg-shaped assembly of 1320 BGO crystals covering polar angles
from 24◦ to 144◦ with a good segmentation of ∼ 6◦ both in the polar and azimuthal directions. Eachcrystal has a sufficient thickness of 220 mm corresponding to 20 radiation lengths. BGOegg has a selfsupporting structure, like a Roman arch bridge, to hold the whole crystals of ∼2t in weight, having noinsensitive area in between adjacent crystals. Consequently, BGOegg provides one of the world’s bestenergy resolutions of 1.3% for 1 GeV photons. This resolution is not the maximum instantaneous value
but is obtainable everywhere in BGOegg, except for the edge regions because of extra electromagnetic
shower leakage at the boundary.
4.1 The η ′ → γγ channel

The energy calibration of BGOegg is one of the most important jobs [10] in the BGOegg experiments.

By employing a huge number of π 0 → γγ events obtained in the experiments, the calibration was madeso as to get the π 0 mass to be the same as the PDG value. We achieved a very beautiful calibration so far

as shown in Fig. 2 for a carbon target with a thickness of 20 mm. This is a kind of overall calibration withno particular momentum-selection for γγ pairs. Nevertheless, the η and η ′ peaks are observed just on
the right places as depicted in Fig. 2. In this calibration we have 548.6±0.1 MeV (PDG: 547.86 MeV) and
959 ± 1 MeV (PDG: 957.78 MeV) for the η and η ′ masses, respectively. The overall γγ mass resolutions

are preliminarily found to be 5.8, 12.9, and 19 MeV for π 0 , η, and η ′ , respectively. Thus BGOegg exhibits
the excellent γγ mass resolutions ever made in meson photoproduction experiments in the world. The

109
10 5

C target (20mmt )π0m(η'): 959(1) MeV
PDG: 957.78
σ(η'): 19(1)

η
10

3

100

m(π0): 134.98(1) MeVη'

PDG: 134.98
5.78
σ(π0):
10 2

counts/5MeV

counts/MeV

10 4m(η): 548.6(1) MeV
PDG: 547.86
σ(η): 12.9(1)

10

80
60
40
20

1
0

200

400

600

800

0
800

900

1000

1100

1200

2γ invariant mass (MeV)

Fig.2. Preliminary results of γγ invariant mass spectra obtained in energy calibration of the
BGOegg calorimeter. Several times of iteration have been made in the calibration so thatthe π 0 mass becomes what it should be.
obtained mass resolutions depend on the target thickness because of no vertex information for γγ events.
We have no way to know the exact vertex point of each event on the macroscopic target, if outgoingparticles are all neutral. We assumed all the events were generated at the center of the target. It is
expected, therefore, to have better γγ mass resolutions with a thinner target.
4.2 The η ′ → π 0 π 0 η channel

The BGOegg calorimeter is one of the most suitable detectors for the measurement of the η ′ →π 0 π 0 η process, being able to detect π 0 π 0 η events by measuring 6γ’s with a good mass-resolution. A
450
400
m

counts/4MeV

350
300
250
200
150
100
50
0
600

700

800

900
0 0

1000

1100

1200

1300

1400

π π η invariant mass (MeV)

Fig.3. A π 0 π 0 η invariant mass spectrum obtained in the γC → π 0 π 0 ηX reaction.
conceivable change of the decay partial width may be detectable by comparing the branching ratio of

110
the π 0 π 0 η channel measured using a nuclear target with that using a hydrogen target. This might be
one of the most promising studies to find chiral restoration phenomena. We reconstruct π 0 π 0 η eventsfrom a bunch of three 2γ events of η ′ → π 0 π 0 η → 6γ. By employing a kinematical fit to π 0 and η
masses, a π 0 π 0 η invariant-mass spectrum is obtained for a carbon target. As shown in Fig. 3, the η ′peak is observed at 958.6 ± 0.3 MeV with a fairy good mass-resolution of σm /m(η ′ ) ≃ 0.67% (σm =6.4 ± 0.3 MeV), which is probably the world best resolution obtained for π 0 π 0 η invariant mass. Theπ 0 π 0 η invariant mass spectrum reveals a clear peak corresponding to the iso-scalar axial vector meson
f1 (1285), the main decay channel of which is known to be f1 → π 0 π 0 η.

§ 5. SummaryThe η ′ meson is a good candidate being able to provide information on the relation between chiralsymmetry restoration and axial U (1) anomaly in the nuclear medium. A small but detectable change
including the effect of a bound state of η ′ is expected to come about in the spectral function of η ′ obtained
through the η ′ → γγ decay process. The experimental data are accumulated for two years with a carbon
and a liquid hydrogen target. The energy calibration has been made successfully, yielding overall γγ

invariant mass resolutions of 5.8 MeV, 12.9 MeV, and 19MeV for π 0 , η, and η ′ mesons, respectively, fora 20 mm thick carbon target. An excellent π 0 π 0 η mass resolution of σm = 6.4 ± 0.3 MeV is obtained at

η ′ mass so far. The data analysis is underway, following a heavy work imposed by ourselves to calibrate
1320 BGO crystals mounted on the electromagnetic calorimeter BGOegg.

Acknowledgment
This work was supported in part by MEXT (Grant No. 19002003), and by JSPS (No. 24244022).

References[1]

Y. Nambu and G. Jona-Lasinio: Phys. Rev. 122 (1961) 345; 124 (1961) 246.

[2]

M. Kobayashi and T. Maskawa, Prog. Theor. Phys. 44 (1970) 1422;
M. Kobayashi, H. Kondo and T. Maskawa, Prog. Theor. Phys. 45 (1971) 1955;
G. ’t Hooft, Phys. Rev. Lett. 37 (1976) 8; Phys. Rev. D14 (1976) 3432.

[3]

H. Nagahiro, M. Takizawa, S. Hirenzaki, Phys. Rev. C74 (2006) 045203;
H. Nagahiro et al., Phys. Rev. C87 (20013) 045201.

[4]

D. Jido, H. Nagahiro, S. Hirenzaki, Phys. Rev. C85 (2012) 032201(R).

[5]

S.H. Hwang et al., Phys. Rev. Lett. 108 (2012) 092001.

[6]

M. Nanova et al., Phys. Lett. B727 (2013) 417; Phys. Lett. B710 (2012) 600.

[7]E. Czerwiński et al., Phys. Rev. Lett. 105 (2010) 122001.

[8]

E. Czerwiński et al., Phys. Rev. Lett. 113 (2014) 062004.

[9]

H. Shimizu, N. Muramatsu, Nuclear Physics News (2017) 27:1, 19.

[10] Y. Matsumura et al., ELPH Annual Report (2014) 95.

ELPH Annual Report, Tohoku University (2017)

111(ELPH Experiment : #2775, #2839)

光量子放射化分析のための光核反応収率の測定
大浦泰嗣 1 , 寺岬仁志 2 , 山口優貴 2 , 原司 2 , 金子純也 2 , 黒岩憲明 2 , 遠藤勇 2 ,三浦義隆 1
1 首都大学東京大学院理工学研究科分子物質化学専攻 （192-0397 東京都八王子市南大沢 1-1）
2 首都大学東京都市教養学部理工学系化学コース（192-0397 東京都八王子市南大沢 1-1）

Radiochemical measurement of photonuclear reaction
yields for photon activation analysis
Yasuji Oura1 , Hitoshi terasaki2 , Yuki Yamaguchi2 , Tsukasa Hara2 ,Jyunya Kaneko2 , Noriaki Kuroiwa2 , Isamu Endo2 , and Yoshitaka Miura1
1

Department of Chemistry, Tokyo Metropolitan University, Hachioji, 192-0397

2

Department of Chemistry, Tokyo Metropolitan University, Hachioji, 192-0397

Relative reaction yields of ( γ, n) reaction induced by bremsstrahlung of maximum end-point energy(E0) of 20 MeV, 25 MeV, and 30 MeV were measured for the target nuclides with mass number from 12
to 204. Relative yields were systematically increased with an increase of target mass number (At ), that
is, a good linear correlation was obtained in double logarithmic plot. Yields for (γ, n) reactions producing
isomers, however, were smaller than the systematic yield. Relative yields for E0 = 25 MeV and 30 MeV
are almost consistent. At At ≥ 80, however, relative yields for E0 = 20 MeV were slightly higher thanthose for E0 = 30 MeV. And relative yield of 12 C for E0 = 20 MeV was about 10 times lower than one for

E0 = 25 MeV or 30 MeV. Using our relative reaction yields, elemental contents can be determined by asingle comparator method without standard samples used for a comparison method.

§ 1 . はじめに
機器放射化分析法は，高感度な非破壊多元素同時分析法の一つで，核反応により安定核種を放射性核種に変換し，これから放出されるγ線を測定して定量を行なう．原子炉中性子による核反応，主として (n, γ) 反
応により生じた放射性核種を利用する中性子放射化分析法 (NAA) が，多くの分野で広く利用されている．
一方，光量子放射化分析法 (PAA) は，電子加速器で発生させた制動放射線による (γ, n) 反応を利用する放射化分析法で，NAA とは異なる核反応を利用するため，NAA では困難な元素の定量も行なうことができ，相補的な関係にある．PAA は NAA と同様に非破壊多元素同時分析法であるが，NAA ほど利用されていな
いのが現状である．この理由はいろいろあると思うが，PAA を利用する上で不便な点の一つは，NAA の様にユーザーが利用しやすいまとまった核反応収率データがそろっていないことであろう．単色光子に対する
核反応断面積 (励起関数) はデータライブラリー (例えば，[1, 2]) があるが，制動放射線での照射にはそのまま利用できないし，元素が限られている．また，光核反応の教科書や総説で良く引用される Kato et al.

112[3]の反応収率曲線は，収率の単位が mole−1 R−1 であり，利用しずらい. そのため，どれくらいの誘導放射能が生成するかの推定が難しい．Segabade et al. [4]は 1983 年に PAA の教科書を著しているが，この書籍に付属している表がもっともよく整備されている PAA のための反応収率に関するデータの一つであると思われる．この表では，58 Ni(γ, n)57 Ni 反応を基準として，最大エネルギー (E0 ) 30 MeV の制動放射線で

1 時間照射したときの誘導放射能比が与えられている. そこで，本研究では，E0 = 30 MeV での 58 Ni(γ,n)57 Ni 反応に対する光核反応収率比をもとめ，Segabade et al. の値を確認すると共に，掲載されていない
E0 = 25 MeV と 20 MeV の制動放射線を照射した時の核反応収率比も測定した．
放射化分析法での元素の定量は，通常，比較法により行なわれる．すなわち，元素質量既知の試料 (比較標準試料と呼ぶ) を未知試料と制動放射線 (または中性子) で同時に照射し，式 (1) で計数率比から定量を行
なう (照射終了直後に減衰補正した計数率は，元素質量に比例する.PAA では，試料をスタック状に並べて照射するので，光子束の補正が必須．)

Nu ϕ
mu ϕ
au
=
=
as
Ns ϕs
ms ϕ s(1)

ここで，a は照射終了直後の計数率，N は核種数，ϕ は光子束，m は定量元素の質量，添え字の u と s はそれ
ぞれ未知試料と比較標準試料を示し，au と as は同じ放射性核種の同じエネルギーのガンマ線計数率である.
通常，未知試料と比較標準試料に含まれる元素の同位体組成は等しいと仮定できるので，N/Ns = m/msとなる．比較法は，あらかじめ定量対象元素を計画し，それらの元素を含む比較標準試料を同時に照射する必要がある. つまり，計画外の元素は，未知試料でそれから生成した放射性核種が検出されても，定量は不可能である. そのため，ある一つの元素の比較標準試料をもちいて，すべての元素を定量することができる
単一コンパレータ法が考案されている. その定量の原理を式 (2) に示す.

Nx ϕx Yx (1 − e−λx t )rx ϵx
ax=
ac
Nc ϕc Yc (1 − e−λc t )rc ϵc(2)

ここで，a は計数率，N は核種数，ϕ は光子束，Y は反応収率，λ は壊変定数，t は照射時間，r はガンマ線放出率，ϵ は検出器の計数効率，添え字の x と c はそれぞれ定量元素と比較標準元素を示す. 既知量 (Nc )の元素 c を未知 (Nx ) 試料と一緒に照射すると，ax /ac ，ϕx /ϕc と ϵx /ϵc は，実験で決めることができるので，あらかじめ，すべての元素で Yx /Yc を求めておけば， Nx を定量できる. 本研究で測定した反応収率比
は，Yx /Yc (c はニッケル) に相当する．NAA では，単一コンパレータ法を汎用化した k0 標準化法 [5, 6]が開発され，ヨーロッパを中心に広く利用されている. 本研究は単一コンパレータ法への適用も視野に入れて，反応収率比の測定を行なった.
本年報では (γ, n) 反応の収率比について報告する.

§ 2 . 実験方法
炭素から鉛までの 41 元素を対象とし，それらの単体，酸化物，あるいは塩化物の試薬約 50 mg を Al 箔
で包み，直径 10 ｍｍのペレット状の照射試料を作った．5～10 個のこの試薬試料を同じ直径の Ni 箔 (厚さ0.04 mm) とともにスタック状に石英管に封入し，東北大学電子光理学研究センターの電子線形加速器にてE0 が 20 MeV，25 MeV，ならびに 30 MeV の制動放射線を 5 分間または 10 分間照射した．各元素の試
薬試料は石英管内での位置や，同時に照射する試料をかえて，複数回照射した．照射後，適度な時間をおいて，試料をそのまま Ge 半導体検出器で複数回測定した．炭素，フッ素試薬，チタン試薬などの一部の試料

113
は，粉末試料を取り出し，新しい Al 箔で包み直してから測定を行なった. また，炭素とフッ素試料は，厚さ 1 mm の銅板ではさみ，測定用試料とした. 試料は，サム効果が無視できるように，検出器から 10 cm
以上離れた位置において，測定した.
定量した誘導放射能から各標的核種の光核反応収率を 58 Ni(γ, n)57 Ni 反応収率との収率比として求めた．

§ 3 . 結果と考察
限られた時間で，なるべく多くの元素に対しての反応収率比を得るために，複数の異なる試薬を同時に照射した. 複数の試料を同時に制動放射線で照射する際は，ビーム軸にそって試料を並べて照射するため，
ビーム上流から下流に向かって，光子束は減少する. そのため，Ni 箔を適当な間隔で並べ，58 Ni(γ, n) 反応で生成した 57 Ni の比放射能により，各試料間の光子束を補正する．一例として，第 1 図に E0 = 30 MeVの制動放射線を 5 分間照射したときの石英管内での 57 Ni の比放射能の変化を積算質量 [7]に対して示す. 正
確に反応収率比を得るには，57 Ni の比放射能の減少率が，各試薬試料中での光核反応生成物の比放射能の減少率と等しい必要がある. そこで，複数個の C 単体，Cr 単体，SrCl2 ，CsCl，Au 箔，PbCl2 ，ならびに Ni 箔を同時に照射し，(γ, n) 反応で生成した 11 C，51 Cr，85 Sr，132 Cs，196 Au，203 Pb，57 Ni の比放射能の変化を調べた. 積算質量に対する各比放射能と 57 Ni 比放射能との比の変化を第 2 図に示す. ここで
57 Ni 比放射能には，積算質量に対する指数関数的変化より各試薬試料の位置へ内挿した値を用いた. いずれの E0 でも，11 C/57 Ni は積算質量とともにわずかに増加し，最下流の試料での比放射能の比は，最上流の試料の約 1.1 倍であった. 炭素以外の試料では，比放射能の比は積載質量に対してほぼ一定で，11 C/57 Ni も含めてほとんどの比放射能の比のばらつきは相対標準偏差で数 %であり，最大で 10%(E0 = 25 MeV での
11 C/57 Ni) であった．

第1図

試料スタック内での 57 Ni 比放射能の変化．

58 Ni(γ, n)57 Ni 反応との反応収率比は，(1) 式から N /N が既知として得られる.
xc

理想的には，対象元

素とニッケルとの化合物，あるいは，対象元素とニッケルの混合試料を照射するのが望ましい (ϕx /ϕc = 1となる) が，ニッケルとの化合物はほとんど存在しないし，均一な混合試料を正確に調製するのは難しい.
そのため，複数枚の既知量のニッケル箔を適当な間隔で試薬試料の間に挟んで照射した．Ni 箔で生成した
57 Ni の比放射能は，第 1 図に示すように試料の積算質量に対して，指数関数的に減少する. 最小自乗法で得た指数関数より，石英管内での各試薬試料位置における 57 Ni 比放射能を計算し，対象核種の比放射能から，反応収率比 Yx /YN i を求めた. この方法 (Ni 箔法と呼ぶ) で得られた反応収率比の確からしさを検討するた

114

第2図

試料スタック内での比放射能の比の変化．(a) E0 =20 MeV．(b)E0 =25 MeV． (c)E0 =30
MeV．

めに，元素は限られるが，塩化物試薬を照射して，35 Cl(γ, n)34m Cl 反応を基準とした反応収率比，Yx /YClも求めた (塩化物法と呼ぶ)．塩化物試薬を用いることにより，試薬の秤量とフラックス補正の実験的不確かさを排除することができ，より確からしい反応収率比が得られると期待される．Yx /YN i は，NiCl2 試薬を照射して得た YN i /YCl から次式により得た.

Yx
YN i
Yx
=
÷
YN i
YCl
YCl

(3)

第 1 表に塩化物法と Ni 箔法のそれぞれで得られた反応収率比を示す. 複数の定量値がある場合は，それらの荷重平均を示した. ほとんどの反応で，30 MeV と 25 MeV での照射共に，塩化物法による反応収率比と Ni 箔法による反応収率比の値は不確かさの範囲内で一致しており，値の比は± 10%の範囲内であった.
斜体で示した値は，Ni 箔法での値と塩化物法での値の比が± 10%～± 20%異なっており，再検討が必要であるが，本研究で Ni 箔法による得られた反応収率比は充分に確からしいと判断できる.
第 1表
標的核種
Cl-35
Na-23
Rb-85
Rb-87
Sr-88
Sr-86
Sr-86
Sr-84
Cs-133Ba-132
Ba-134Ba-136
Pb-204生成核種
Cl-34m
Na-22
Rb-84
Rb-86
Sr-87m
Sr-85m
Sr-85
Sr-83
Cs-132
Ba-131
Ba-133m
Ba-135m
Pb-203

異なる方法で定量した反応収率比の比較

30 MeV塩化物法
Ni 箔法
0.168 ± 0.008 0.175 ± 0.003
0.360 ± 0.035 0.379 ± 0.013
6.59 ± 0.34
5.99 ± 0.55
5.92 ± 0.32
6.19 ± 0.57
3.87 ± 0.09
4.14 ± 0.89
3.62 ± 0.1
3.73 ± 0.81
5.41 ± 0.13
5.91 ± 1.31
4.59 ± 0.16
6.33 ± 2.21
12.4 ± 0.3
11.5 ± 1.1
12.0 ± 0.8
11.1 ± 1.1
2.49 ± 0.12
2.53 ± 0.23
2.86 ± 0.13
2.67 ± 0.24
未測定40.8 ± 1.4

25 MeV塩化物法
Ni 箔法
0.167 ± 0.007 0.182 ± 0.011
0.339 ± 0.03 0.364 ± 0.016
6.68 ± 0.62
6.80 ± 0.64
6.95 ± 0.64
7.08 ± 0.67
4.7 ± 0.36
4.19 ± 0.11
4.47 ± 0.38
3.84 ± 0.13
6.84 ± 0.64
5.87 ± 0.17
5.77 ± 0.46
5.10 ± 0.19
13.1 ± 1.2
16.0 ± 0.5
12.6 ± 1.2
12.8 ± 1.1
2.75 ± 0.23
2.78 ± 0.2
2.88 ± 0.24
2.92 ± 0.2
41.3 ± 3.5
42.7 ± 1.2

最大エネルギーが 20，25，ならびに 30 MeV の制動放射線で照射したときの (γ, n) 反応の反応収率比(複数の測定値の加重平均) を第 3 図にそれぞれ示す. 核異性体などの親核種が存在する場合は，放射平衡115状態での放射能から反応収率を求めた. いずれのエネルギーにおいても，多くの反応収率比は標的核質量数(At ) の増加と共に累乗関数的に増加した．○で示した核異性体を生成する反応収率比は，●の基底状態核よりも反応収率比が一般的に小さく，これらは相対的に生成しにくいことがわかった．E0 が 25 MeV での反応収率比と 30 MeV での反応収率比は全 At 領域で類似した値であるが，20 MeV での値は，At が約 80より大きい領域では，25 MeV または 30 MeV の値より大きく (最大で約 3 倍)，また，12 C の値は約 10 倍小さい. 原子核での光子による巨大共鳴が生じるエネルギーは At が小さいほど高い．12 C では約 24 MeV[1]であり，E0 = 20 MeV ではこのエネルギーに達しず，かつ，12 C(γ, n)11 C 反応のしきいエネルギーが18.7 MeV と高いため，収率が小さくなったと考えられる. 第 2 表で本研究で得られた E0 = 30 MeV での反応収率比を文献値 [4, 8]と比較した. Segebate et al. の値は，比較できるように彼らの 1 時間照射時の放射能比の値から反応収率比を計算した値である. それぞれの核反応で本研究での値を含め 3 つの定量値があるが，これらの値が 3 つとも等しい反応は一つもなく，どれか一つが他と異なっている. 89 Y，90 Zr，
204 Pb 以外は，本研究での定量値は，2 つの文献値のどちらかと一致した．第 2 表を含めて本研究で定量したすべての反応では，本研究での定量値は Segebade et al. の値よりも小さく，多くは Segebade et al. の値の 1/2 倍から 1 倍の値であった. 一部の反応では，100 倍以上，あるいは 1/100 倍以下異なる値もあった．値が一致しない原因は現在のところ不明である.

第3図

58 Ni(γ, n)57 Ni 反応を基準とした (γ, n) 反応の反応収率比．(a) E =20 MeV．(b)E =250
0
MeV． (c)E0 =30 MeV．グラフ内の点線は傾向を表す目安．

§4 . ま と め
炭素から鉛までの 41 元素で，最大エネルギーが 20 MeV，25 MeV，30 MeV の制動放射線を照射した
ときの (γ, n) 反応の反応収率比を 58 N i(γ, n)57 N i 反応を基準にして求めた. 反応収率比は，標的核質量に対して系統的に変化した. 今後，58 N i(γ, n)57 N i 反応の絶対反応収率を得ることで，絶対収率に変換可能である. 本研究で求めた値は Segabade et al. の値よりも全体的に低い値であった. 単一コンパレータ法による標準試料の光量子放射化分析を行ない，定量値からどちらの値がより正確か判断するとともに，異なった原因を解明していく予定である. また，(γ, 2n) 反応や (γ, pxn) 反応による生成核種も検出されているので，これらの反応収率比も求め，報告する予定である．

116

標的核
C-12
Na-23
Ti-46
Ca-48
Cr-52
Mn-55
Ni-58
Co-59
Cu-65
Y-89
Zr-90
Hg-198Tl-203
Pb-204

謝

生成核
C-11
Na-22
Ti-45
Ca-47
Cr-51
Mn-54
Ni-57
Co-58
Cu-64
Y-88
Zr-89
Hg-197
Tl-202
Pb-203

第 2表

反応収率比の文献値との比較

本研究
0.132 ± 0.003
0.379 ± 0.013
1.43 ± 0.13
2.54 ± 0.14
2.53 ± 0.07
2.80 ± 0.12
1
3.47 ± 0.16
5.13 ± 0.24
6.46 ± 0.23
5.74 ± 0.22
未測定
23.1 ± 1.3
40.8 ± 1.4

Masumoto et al. (1978) [8]
0.12
0.368
1.54
9.76
2.89
3.56
1
3.24
4.96
8.56
7.18
24.6
33.6
32.9

Segebade et al. (1983) [4]
未測定
0.51
1.9
2.8
5.2
2.7
1
4.5
6.7
8.1
7.2
5.9
28
35

辞

制動放射線照射では，菊永英寿准教授と塚田暁助教をはじめ，電子光理学研究センタースタッフの方々に大変お世話になりました．この場を借りて深く御礼申し上げます．

参

考

文

献

[1]

IAEA-TECDOC-1178 (2000) 72.

[2]

N. Iwamoto et al.: JAEA-Conf 2016-004 (2016) 53.

[3]

Kato : J. Radioanal. Chem. (1973) 307.

[4]

C. Segabade et al.: ”Photon Activation Analysis” de Gryter (1983).

[5]

A. Simonits et al.:J. Radioanal. Chem. 24 (1975) 31.

[6]

米沢，松江: ぶんせき No.2 (2004) 75.

[7]

大浦他: 核理研報告 32 (1999) 42.

[8]

K. Masumoto et al.: Nucl. Instr. Meth.157 (1978) 99.

ELPH Annual Report, Tohoku University (2017)117(ELPH Experiment : #2885)

Identification of Elemental Composition and Preparation ofRadio-tracer for Recovery of Rare Metals in Household
Garbage Incineration Slag by Photon Activation Method.
K. Akiyama1,∗ , K. Ito1 , S. Kubuki1 , and H. Kikunaga2
1

Department of Chemistry, Tokyo Metropolitan University, Hachioji, Tokyo 192-0397

2

Research Center for Electron Photon Science, Tohoku University, Sendai, 982-0826

Chemical composition of household garbage incineration slag supplied in September, October, andNovember, 2017 from Tamagawa incineration plant were determined by Photon Activation Analysis under the conditions of maximum electron beam energy of 20 MeV with 0.1 mA beam current at ResearchCenter for Electron Photon Science (ELPH) of Tohoku University. Amount of determined elements were
almost same as each other and almost consistent with the abundance in Earth ’s crust except for Ca, Cr,and some undetermined elements. In conclusion, it is necessary to investigate the element compositionof incineration slag continuously in the future.

§ 1. Introduction

Amount of burnable garbage emitted from households is estimated to be about 650 million tons

annually in OECD member countries, and also in japan it is estimated to be about 50 million tons per
year [1]. Although these garbage are usually incinerated and then buried as incineration ashes, there
are same problems, such as securing the site for the burial disposal, because the emissions of theseincineration ashes are enormous. In Tokyo, it is attempted for the improvement of the site problems to
reduce of volume by melting and vitrifying of incineration ash and also to reuse these vitrified ash as
the roadbed materials, the concrete aggregate, and the agent for the soil improvement. [2]Kubuki and co-workers reported the chemical composition of vitrified ash of incinerated household
garbage (incinerated slag) by induced coupled plasma optical emission spectroscopy (ICP-OES) measurements of their nitric acid solution and also the similarity of their composition with aluminosilicate
including iron [3]. It is known that the vitrified solids of aluminosilicate indicate the decomposing abilityof organic materials under the light irradiation [4]. If the incinerated slag of similar chemical composition with aluminosilicate indicates the decomposing ability of organic materials, it is possible to use theincinerated slag for the environmental purification, such as water purification, it could be expected as
the new effective way to use of incinerated slag. However, incinerated slag contains many impurities,
unlike aluminosilicate glass synthesized from the reagents. Since the impurities in incinerated slag include valuable metal elements such as cobalt and manganese, if it is possible to recover these elements∗

Correspondence Address: Department of Chemistry, Tokyo Metropolitan University, Hachioji, Tokyo
192-0397

118
by chemical separation, it will lead to effective use of waste so called ”Urban mine” and also to a solution
to the universal theme in the contemporary society.
In this study, we aim to recover valuable metal elements from incinerated slag and to develop therecovery method by chemical separation. In this paper, we report the validity of chemical composition in
incinerated slag per collecting month quantified by photon activation method.

§ 2. Experimental

Approximately 100 mg of incinerated slag collected in September, October, and November, 2017,

were powdered with a handy agate mill. These powdered slag were wrapped in high purity aluminum
foil, and then sealed under reduced pressure in a quartz tube for the irradiation with bremsstrahlung.
we used JB-1a, whose elemental composition is quantitatively well assigned in National Institute ofAdvanced Industrial Science and Technology (AIST) Geological Survey of Japan, as the comparative
standard for the photon activation analysis. Irradiation with Bremsstrahlung was carried out at Tohoku
University, Research Center for Electron Photon Science (ELPH) under the conditions of maximum
electron beam energy of 20 MeV, 0.1 mA. After that, γ ray emitted from samples were measured with ahigh purity Ge semiconductor detector (SEIKO EG&G).

§ 3. Results and Discussion

Figure 1 shows the γ ray spectra of slag samples collected in September (Slag09), October (Slag10),

and November (Slag11), 2017, respectively. These spectra were obtained after about 2 weeks from theend of bombardment. It is presumed that the compositions of elements with high sensitivity in thephoton activation are qualitatively very similar because these three spectra are closely similar to eachother.

Fig.1. γ ray spectra of a) Slag09, b) Slag10, and c) Slag11 samples.

Table 1 indicates the elemental concentration determined by γ-ray analysis for each slag sample.

119
Almost all of determined elements in a slag are consistent with each other so that the variation ofelemental composition in studied slag samples is found to be little. In addition, it could be seen that theelemental composition of these slags are not so much different from the element abundance in Earth’s
crust, except for calcium and chromium.
Table 1. Preliminary Concentration of Slag Sample Determined from γ-ray Measurements.
Element
Ca
Fe
Al
Mg
Ti
Na
Mn
Cr
Sr
Zr
Ni
Rb
Co
Nb
Zn
Y
Sc
As
Ce
Se
Au

Abundancein Earth’s Crust
5.0%
6.3%
8.2%
2.9%
0.70%
2.3%
0.11%
140 ppm
360 ppm
130 ppm
90 ppm60 ppm30 ppm17 ppm79 ppm29 ppm26 ppm
2.1 ppm
60 ppm50 ppb
3.1 ppb

Slag09Slag10

Slag1119.3±2.5%
6.2±0.18%
2.73±0.21%
1.869±0.011%
1.68±0.13%
1.244±0.032%
0.1924±0.0011%
1159±11 ppm
700±180 ppm
127±16 ppm
56±34 ppm
45±13 ppm
38.72±0.57 ppm
18.77±0.87 ppm
16±11 ppm
13.12±0.50 ppm
5.0±1.0 ppm
1.15±0.29 ppm
0.34±0.24 ppm
10.5±2.7 ppb
0.44±0.12 ppb

22.81±0.99%
6.12±0.13%
2.96±0.13%
1.96±0.28%
1.62±0.10%
2.397±0.036%
0.2444±0.0023%
1221±24 ppm

22.4±1.0%
7.62±0.18%
3.17±0.12%
2.10±0.29%
1.511±0.076%
2.436±0.032%
0.2525±0.0022%
1314±25 ppm

154±15 ppm
78.4±8.4 ppm
11.02±0.80 ppm
27.0±2.4 ppm
22.74±1.2 ppm
32±10 ppm
16.1±1.0 ppm

143±17 ppm
128±10 ppm
10.9±1.2 ppm
36.1±1.8 ppm
25.4±1.5 ppm
28.1±9.0 ppm
15.56±0.65 ppm

0.419±0.028 ppm

0.474±0.027 ppm

Table 2 is list of the elements which could not be determined because γ-ray peaks were able to beobserved in slag samples but γ-ray peak in JB-1a used for a comparative standard could not be observed
because of their low concentration or low sensitivity. It is expected that these elements show sufficiently
higher concentrations than the element concentrations in JB1a and the Earth’s crust, and it can beconsidered that these elements should be noted in the study of the recovery of valuable metal elementsin the future work. In conclusion, it is necessary to investigate such variation in element composition
continuously in the future.

Acknowledgment
We deeply thank to the facility staffs of research center for electron photon science at Tohoku University for supplying the high-quality electron beam. And also we thank to Doctor Kyo Tsukada for
helping us in the sample irradiation. This work was partly supported by Tokyo Metropolitan Goverment(Advanced research program).

120
Table 2. Undetermined Elements Observed in Slag samples.
Element
Ag
Ba
Cs
Cu
Nd
Pt
Sb
Te

Abundancein Earth’s Crust
80 ppb340 ppm
1.9 ppm
68 ppm33 ppm3.7 ppb
0.2 ppm
1 ppb

JB-1a
Concentration
41.0 ppb
504 ppm
1.31 ppm
56.7 ppm
26.0 ppm
1.60 ppb
0.25 ppm
NA

Observed Sample
<
<
<
<
<
<
<
<

Slag09Slag09, Slag10, Slag11
Slag09Slag09Slag10, Slag11
Slag09Slag09, Slag10, Slag11
Slag09, Slag10, Slag11

References[1]OECD, “ Municipal Waste ”, in OECD Factbook 2015-2016: Economic, Environmental and Social
Statistics, OECD Publishing. DOI: 10.1787/factbook-2015-en (2016).

[2]

Waste Report ed. Clean Authority of Tokyo, (2018) vol. 23, p. 7.

[3]

S. Ishikawa, B. Kobzi, K. Sunakawa, S. Nemeth, A. Lengyel, E. Kuzmann, Z. Homonnay, T.
Nishida, S. Kubuki, Pure Appl. Chem., 89, 535 (2017).

[4]

Y. Iida, K. Akiyama, B. Kobzi, K. Sinkó, Z. Homonnay, E. Kuzmann, M. Ristić, S. Krehula, T.
Nishida, S. Kubuki, J. Alloys Compd., 645, 1 (2015).

ELPH Annual Report, Tohoku University (2017)

121(ELPH Experiment: #2887)

Radioactive phantom productions for PET and β-ray imaging system
T Fukuchi1, H. Haba2, and H. Kikunaga3
RIKEN Center for Biosystems Dynamics Research, Kobe, 650-0047 JapanRIKEN Nishina Center for Accelerator-Based Science, Wako, 351-0198 Japan
3
Research Center for Electron Photon Science, Tohoku University, Sendai, 982-0826 Japan1

2

We have been developing imaging systems for nuclear medicine. In order to test theperformance of developing imaging systems, we have produced radioactive phantoms using the photodissociation reactions. Produced phantoms were a volumetric 44Ti/44Sc phantom for a PET imaging
and thin 22Na phantoms for a β-ray imaging system. We performed imaging experiments using thesephantoms and assessed the basic performance of the developing systems.
§1. Introduction
We have been developing the next-generation nuclear medicine imaging systems. One is amultiple-isotope PET (positron emission tomography), and the other is a β-ray imaging system. Bothsystems are designed to make coincidence with γ-ray using the additional detectors. Therefore, using
β-decay nuclide, which promptly emits de-excitation γ-ray emission (so-called positron-γ emitter or
β-γ emitter) as a tracer, the γ-ray coincidence enables identification of nuclide or improvement of theimaging qualities.
Figure 1 (a) shows a photographof our developed PET system. Thissystem is composed of a PET
system and additional γ-ray
detectors. The PET system consistsofpixelized
gadolinium
orthosilicate (GSO) scintillation
detectors and has a ring geometry
with 95 mm in inner diameter and37.5-mm width. The additional
detectors are eight bismuth
germanium
oxide
(BGO)
scintillation detectors, each ofwhich has size of 50 × 50 × 30
mm3, arranged in two rings
mounted on each side of the PET
ring [1].

Fig. 1. (a) Our developing PET system with additional γ-ray
detectors. (b) Produced 44Ti/44Sc phantom for PET imaging.
(c) An example of reconstructed image of the 44Ti/44Sc
phantom.

Figure 2 (a) shows a photographof the developed β-ray imaging
system. The system consists of aposition sensitive β-ray detector and a large volume γ-ray detector. These detectors were mounted on

122

the flexible frames and can locate on the arbitrary positional relations. A 35×35×1 mm3 La-GPS(Ce)scintillator pixelized in 300-µm pitch by a grooving process [2] was employed for the β-ray detection.
A bismuth germanium oxide (BGO)
scintillator with a size of 50×43×16
mm3 coupled to a photomultiplier tube
was used as a γ-ray detector.
In order to evaluate the performancesof our developed systems, it is necessary
to perform the phantom imaging
experiment, which visualize the alreadyknown radio-tracer distributions.
Therefore, we carried out experiments to
produce the 44Ti and 22Na phantoms.
Titanium-44 decays to the 44Sc with59.1 years physical half-life and 44Sc is apositron-γ emitter with a half-life of 3.95
hours. Sodium-22 is also a positron-γ
emitter with a half-life of 2.6 years andemits a prompt γ-ray with energy of 1275
keV. Therefore, both nuclides are usefulfor performance test of our developed
systems.

Fig. 2. (a) Our developing β-ray imaging system withadditional γ-ray detector. (b) Produced 22Na phantoms
and experimental setup. (c) An example of reconstructed
image of the 22Na phantoms.

§2. Experiments
2.1 44Ti/44Sc phantom
Since PET can provide 3-dimensional distribution of a tracer, the phantom should have 3dimensional distribution for the performance test. Accordingly, we prepared a natural Ti target of acylindrical shape with 8 mm in diameter and 5-mm thickness (Fig. 1 (b)). A natural existing ratio of
46Ti is 8%, and 44Ti was produced using a photo-dissociation reaction of 46Ti(γ,2n)44Ti. The production
experiments were performed at Research Center for Electron Photon Science (ELPH) in Tohoku
University. The enclosed target was placed in the back of a platinum converter and cooled with running
tap water. The accelerator was operated for 3 hours irradiation at an electron energy of 50 MeV witha mean current around 100 µA.
2.2 22Na phantoms
Owing to the short flight range of β-ray in a material, the β-ray imaging is restricted to imaging
for a 2-dimensional object. Therefore, we prepared the 5 thin disk shape targets for the test of the βray imaging system. These targets were made of natural Mg (24Mg isotope ratio: 79%) and has 8 mm
in diameters and 0.21-mm thicknesses with alphabetic characters “RIKEN” of 1 mm width mortising.
The 3 hours irradiation was performed by the ELPH accelerator in a similar manner with 44Ti
production using 24Mg(γ,pn)22Na reaction with electron energy of 50 MeV.
§3. Results
3.1 PET imaging
The produced radioactivity in a 44Ti cylindrical phantom was 38 Bq. An imaging experiment for
44Ti/44Sc cylindrical rod using our developed PET system were performed for 12 hours. From the123reconstructed image of a 44Ti/44Sc phantom as shown in Fig. 1 (c), we confirmed that our developed
PET system has ability to visualize the tracer distribution with low activity by a long hour ofmeasurement. This result indicates our developed system is useful for not only a nuclear medicine but
also an activation analysis or non-destructive test in the industrial field.
3.2 Beta-ray imaging
The produced total radioactivity of 22Na phantoms is 3.4 kBq. For these phantoms, ameasurement using our developed β-ray imaging system was performed for 10 min. Figure 2 (b) shows
photograph of experimental setup. Five phantoms were measured at the same time. From thereconstructed image shown in Fig. 2 (c), the alphabetic characters on phantoms can be easily
recognized and we find that our developed β-ray system had about 0.5 mm imaging resolution.
Acknowledgements
The authors thank to the facility staffs of ELPH in Tohoku University for supplying the highquality electron beam. The authors thank Prof. Yamamoto for the development of the imaging devices.
This work was supported by JSPS KAKENHI Grant Number JP15H04770.
References[1] T. Fukuchi et al.: Medical Physics 44 (6) (2017) 2257.
[2] S. Yamamoto et al.: Journal of Instrumentation 13 (2018) P05028.
[3] National Nuclear Data Center, Brookhaven National Laboratory. http://www.nndc.bnl.gov/.

124

III. Status ReportELPH Annual Report, Tohoku University (2017)

125

Status of Accelerator Facilities in FY2017
Accelerator groupResearch Center for Electron Photon Science, Tohoku University, Sendai, 982-0826

The electron accelerator complex: high intensity 60 MeV linac, 90 MeV injector linac and 1.3 GeV
BST (booster-storage ring), had been regularly operated for user time in FY 2017 and the total operatingtime exceeded 2000 hours including the operation of the test accelerator t-ACTS. A large-scale replacement and renovation work in the indoor electrical substation were conducted in the end of FY2017. In
the same time, the Experimental Hall No. 1 was also renovated in order to secure the safety in handlingthe non-sealed RI material, and thus all the machine time was suspended for more than three months.
In this report, machine status and some improvements are reported.

§ 1. Machine operation
1.1 High intensity linac

For the high intensity linac, the operating beam time in FY 2017 reached 240 hours. The electron
beam with the energy ranging from 10 to 60 MeV was supplied depending on a requirement of individualmachine user. The typical beam current was 120 µA for 50 MeV operation. Although the machine time
was performed almost as scheduled, there were some minor troubles in the linac. Those troubles weremainly caused by an aging phenomenon of the machine components, such as the degradation of a signal
cable for the current monitor and a breakdown of power supply for NIM crate, etc. A high-voltage control
for the electron gun has also trips sometimes due to the failure of the inverter power supply; however
the detailed cause is still under investigation. The other minor trouble is so-called “vacuum explosion”,
in which the vacuum pressure of beam line suddenly increases and finally results in a suspension of themachine operation because of the trip of ion pumps. Since the deterioration of the ion pumps themselves
was presumed, some ion pumps in the downstream part of the accelerating structure were replaced
partially.
1.2 Injector linac
The injector linac has stably supplied electron beam with the energy of 90 MeV to BST ring. In
these years, however, the thermionic rf gun had a problem that discharges at the cathode cell in the
gun have been frequently observed due to deposition of carbon-like matter between the cathode and thecavity wall. Such discharges has begun to occur at around one year after the installation of new cathode.
Although the reason for the deposition is still under investigation, currently we have coped with thisproblem by replacing the cathode once a year. As the other minor troubles, there are failures in cooling126
water system which trip the rf modulator. The malfunction of the flow switches is suspected, so that itis planned to replace these suspicious switches.
1.3 BST ring
1.3 GeV BST ring has also well operated to generate high energy gamma rays via bremsstrahlung
from internal target wire inserted to the electron beam orbit. Generated gamma rays are not only
utilized to the experiment for quark/hadron physics, but also supplied to the test beam line for testingof detectors used in high energy experiments. There were two major troubles in FY2017; one was a
breakdown of movable tuner installed in an rf cavity and the other one was a trouble in a power supply
of a bump magnet. For both troubles it took more than half a day to restart the user time. Some otherminor troubles in BST operation have also occurred and those sources are mainly recognized to be anaged deterioration similar to the high intensity linac. Especially, the aging phenomenon in the klystronpower supply for the rf cavity is serious, and thus a project to replace the old klystron to a new rf source
based on the solid-state amplifiers is under consideration.

§ 2. Facility improvements

2.1 Replacement and renovation work in indoor electrical substation
So far, updates of aged electric facilities have been carried out over the past three times. Startingwith the renewal of the gas circuit breaker of the extra-high voltage substation in FY2007, in FY2009
the transformers of the substation and an emergency power generator in the indoor substation wererenewed, and in FY2013 and FY2014, control panel and some transformers in the indoor substation were
updated. Then all remained transformers and low voltage switchboard in the indoor substation were
finally updated at the end of FY2017. Also, as a countermeasure against rain leakage due to the agingof buildings, roofs and exterior walls were also refurbished. It took more than three months to complete
these replacement and renovation works. Figure 1 shows the inside of the indoor substation before
and after the update. Transformers and switchboards, where dangerous high voltage terminals were
exposed, were replaced by safe and compact modular equipment. Moreover, in addition to updating theold transformers which had somewhat of losses, the connection of the load equipment was also adjusted
so that the load during operation is balanced. Due to this update, the maximum power consumption
during accelerator operation is also slightly reduced.
2.2 Renovation of the Experimental Hall No.1
For RI production and research on nuclear and radiochemistry, the electron beam from the highintensity linac is transported to the Experimental Hall No. 1 and then irradiated to various targets
arranged in the irradiation apparatus placed just before the beam dump. In response to the new guidance of the Nuclear Regulatory Agency on the handling of unsealed RI sources (limited use under theencapsulated condition) an extensive renovation was carried out at the end of FY2017 in conjunction
with renovation of the indoor electrical substation. The main contents of this work are floor and wall

127

Fig.1.

Transformers and switchboards in the indoor substation before (upper picture) and after
the replacement (lower). The renovation of the indoor substation was also performed.

treatment to prevent infiltration of the radioactive material, and renovation of the drainage route. In
the renovation of the floor surface, concrete was filled in all the piping pits provided on the floor, andthe floor surface was also ground and smoothed. After that, painting and coating treatment with 2 mm
thickness was applied using epoxy resin with radiation resistance capability. The wall surface was also
treated using the same epoxy resin type material with 0.2mm thickness. The inside of the Experimental
Hall before and after renovation work is shown in Fig. 2.

§ 3. Construction plan of new beam line

In the coming shut down period, it is planned to construct a new beam line to conduct an experiment

for electron scattering with extremely low energy transfer, which is aiming to solve the “Proton Radius
Puzzle” [1, 2]. This experiment requires high quality electron beam with very small energy spread ofless than 0.1 % and variable beam energy of about 20 to 60 MeV. The new beam line and a spectrometerfor the experiment will be placed in the Experimental Hall No. 1, and share the beam from the highintensity linac with the present RI beam line. At present, a lattice modification of the transport linefrom the linac, installation of additional beam monitor and beam slit, etc. are under preparation inadvance of the construction of the new beam line.

128

Fig.2.

Renovation of wall and floor in the Exp. Hall No.1. Upper picture shows an end part ofthe beam line in the experimental hall before the renovation. Lower picture shows thereconstructed shield blocks after the renovation.

References[1]

Randolf Pohl et al., Nature vol. 466, 213 (2010)[2]

Aldo Antognini et al., Science vol. 339 , 417 (2013)

ELPH Annual Report, Tohoku University (2017)

129

User Support Office Report in FY2017
M. Miyabe1 and The user support office1
1

Research Center for Electron Photon Science, Tohoku University, Sendai, 982-0826, JapanThe User Support Office coordinate across the users and our facility for management of the beamtime. In 2017 financial year, we had provided the electron, photon and positron beam without apparent
problems except for Photon beamline I. From Jan to Mar 2018, we couldn’t provide any user beam-time
because of the repairing work of electric room.

§ 1. Introduction

ELPH has three accelerators for Joint Usage/Research. Our facility could provide several beams

with following three beam lines,• 70 MeV electron linear accelerator (linac) at the first irradiation lab (For Radiochemistry)• Tagged photon beam from 1.3 GeV electron synchrotron called BST ring with 90 MeV injector at
the second irradiation lab (For Hadron Physics, Photon beamline I)• Tagged photon beam at the GeV-γ irradiation room (For Hadron Physics, Photon beamline II)

In addition, positron/electron beam line for testing detectors is located at the GeV-γ irradiation room.
The 70 MeV electron linear accelerator was utilized for the Radiochemistry experiments by photonuclear reactions. It could produce radio active source with its high intensity. Both tagged photon
beam line was used for Hadron physics experiments. NKS2 and FOREST/BLC experiment have bean
held in recent years.

§ 2. Beamtime operated

The total radiation time was 239 hours for the RI linac operation and 1658 hours for the BST

operation, and it was 1898 hours in total. The beam provided time (user beamtime) was 1629 hours for
the BST operations. Table 1 summarizes the radiation times, and user beam times in fiscal.
Many experiments for testing detectors were made by positron beam line. Positron beam was produced by bremsstrahlung photon beams from the synchrotron. Total 35 shift experiments are performed
using this positron beam in this financial year.
A Next generation FOREST experiments (FOREST/BLC) was started by GeV-γ group in ELPH.
New bending magnet was installed on the downstream of FOREST detectors and it covers the most forward angle. These new experimental setup enable the zero degree proton detection for the γd → pηnreaction at Eγ ∼ 0.9 GeV. This reaction gives the zero relative momentum between the η and n. This sit-uation will enable to determine the ηn scattering length. In this financial year, New spectrometers were130
installed in the downstream of BLC magnet, and the pilot experiment of FOREST/BLC was performed.
In Photon beam line I, The photon beam was recovered after the repairs for the radiator driving
system, NKS2 experiment will carry out in next financial year.
one experiment was carried out for the undergraduate students. this experiment (#2884: N. Muramatsu, ELPH, Tohoku University) is for the education of the undergraduate students in ELPH.
Table 1. Radiation times, and user beamtimes in financial year 2017. They are given by the sumof the times that the beam is coming to the beamline, and that the beam is provided tothe users.
RI Linuac
BST RingMonthradiation (h) radiation (h) user (h)
April
2
253
256
May
16
238
234
Jun
29
222
229
July
8
12
13
August000September
14
20
October
69
84
81
November
27
626
592
December
74
222
218
January000
February
0
0
0
March
0
0
0
Sum
239
1658
1629

§ 3. ELPH workshops and ELPH seminars

In this fiscal year, ELPH supported four ELPH workshops. The first one is hadron physics (C020:

H. Kanda, Kyoto University), the second one is hadron physics (C019: T. Ishikawa, ELPH Tohoku University), the thirds is SNP school 2017 (C017: S. N. Nakamura, Tohoku University), the fourth one isaccelerator physics (C018: H. Zen, Kyoto University).
17 ELPH seminars were held in this fiscal year. Seminars title and talker are listed below.
• Shuo Wang, Shandong University, China JinPing underground Laboratory for Nuclear Astrophysics”• T. Ishikawa, ELPH, ”η photoproduction on the deuteron at Eγ <1.2 GeV”

• Y. Tsuchikawa, Nagoya University, ”Experimental study for the “ neutron anomaly ”via neutralkaon photoproduction at ELPH”• KIM, Hyun-Chul, Inha University, ”Structure of the N ∗ (1685) resonance”• N. Tsukamoto, Tohoku University, ”陽子形状因子の解析と電荷半径及びその不定性”• T. Iijima, KMI Nagoya University ”Heavy Flavor Hadron Physics at SuperKEKB/Belle II”• M. Kando, QST, ”高強度レーザーを用いた電子加速の研究の進展と高強度場科学”• K. Ishida Riken ”ミュオン水素原子の超微細構造エネルギー測定による陽子 Zemach 半径決定”• H. Sakai KEK ”EURO-XFEL の建設に携わって（DESY １年間滞在中の EURO-XFEL の超伝導空洞の量産化試験と XFEL 発振に至るまで）”

131• T. Ohtsuki, Sophia University, ”深層学習を用いたランダム電子系の量子相転移の研究”• G. Mitsuka, Riken ”200GeV pp/pA 衝突における前方中性子の横偏極単スピン非対称と ultra-peripheral
collision を用いた解釈”• H. Tanida, JAEA ”Λc 崩壊と Kp → Λη 反応における新しい Λ 共鳴の可能性”• H. Nohmi, RCNP, ”重いクォークを含むバリオンの分光研究：J-PARC の実験からわかること”• Steven Karataglidis, University Johannesburg, ”Exploring exotic nuclei within the MCAS framework”• Carlo Barbieri, University Surrey, ”Self-Consistent Green’s Function Studies of Medium Mass Isotopes”• S. Narita, Iwate University ”凝縮系核科学の概要と最近の状況”• Carlos Bertulani, Texas A&M, ”Electromagnetic Probes of Exotic Nuclei”• Oleg Denisov, INFN-Torino and CERN, ”Future QCD facility at SPS (CERN) extracted beams”

132

ELPH Annual Report, Tohoku University (2017)

Radiation Safety Report 2017
Radiation Safety Office

放射線安全管理室より、㻞㻜㻝㻣 年度（平成 㻞㻥 年 㻠 月～平成 㻟㻜 年 㻟 月）の報告を以下の通り行う。㻌

§㻝．㻌 許認可申請
㻴㻞㻥 年㻌 㻠 月㻌 㻟 日㻌 㻌 放射線取扱主任者㻌 選任㻌 石川貴嗣㻌（㻴㻞㻡 年 㻢 月 㻝 日㻌 選任㻌 菊永英寿（正）、武藤俊哉）㻌
㻴㻞㻥 年㻌 㻣 月 㻝㻝 日㻌 㻌 定期検査・定期確認（㻴㻞㻥 年 㻣 月 㻞㻡 日㻌 合格・適合）㻌
㻴㻞㻥 年㻌 㻤 月㻌 㻥 日㻌 㻌 変更承認申請㻌
㻴㻞㻥 年 㻝㻜 月㻌 㻠 日㻌 㻌 承認㻌
（変更の内容）㻌
㻝．非密封同位元素使用施設の変更（作業室，汚染検査室の追加）
㻞．非密封同位元素使用核種および数量の変更㻌
㻟．下限数量以下の非密封放射性同位元素の管理区域外使用の核種の㻌追加㻌
㻠．㻣㻜㻌㻹㼑㼂㻌 電子線形加速装置のビームライン変更（㻟㻚㻡㻌㼙㻌 延長）㻌㻡．㻡㻜㻌㻹㼑㼂㻌 電子線形加速装置の使用時間の変更㻌
㻢．インターロック動作の変更㻌
㻣．放射化物保管容器の変更㻌
㻤．使用施設の変更（作業室，汚染検査室の材質の変更）㻌
㻥．排水経路の変更（使用施設，クライストロン室入口の流しの追加）㻌

§㻞．㻌 個人管理㻞㻚㻝㻌 放射線業務従事者登録
㻞㻜㻥 人（㻌 東北大㻌 㻢㻤 人㻌 学外㻌 㻣㻣 人㻌 研究者以外㻌 㻢㻠 人）㻌

㻞㻚㻞㻌 個人被ばく管理㻌㻝 年間の個人被ばく線量㻌 㻌 㻡㻌㼙㻿㼢㻌 以下㻌 㻞㻜㻥 人㻌133㻞㻚㻟㻌 教育訓練㻌
定期講習㻌
平成 㻞㻥 年 㻣 月 㻝㻥 日㻌 登録前教育 㻝㻜 人㻌 再教育 㻢㻥 人㻌
特別講演の内容：㻌
青森県エネルギー総合対策局量子科学センター開設準備室㻌 一戸㻌 浩二㻌 氏㻌
「青森県量子科学センターの概要」㻌
不定期の講習㻌
再教育㻌 㻝㻥 回㻌 㻞㻤 人㻌
登録前教育（新規教育）㻌 㻞㻠 回㻌 㻝㻜㻟 人㻌§㻟．自主点検年 㻞 回実施㻌 㻌 平成 㻞㻥 年 㻥 月 㻞㻥 日、平成 㻟㻜 年 㻟 月 㻝㻠 日

§㻠．放射性同位元素製造記録
㻞㻜㻝㻣 年度に本加速器施設で製造され，共同研究に使用された放射性同位元素は次の通りである。
核種㻌

数量㻌 㻔㼗㻮㼝㻕㻌㻹㼚㻙㻡㻠㻌

㻠㻭㼡㻙㻝㻥㻢㻌

㻝㻘㻣㻜㻜㻹㼛㻙㻥㻥㻌

㻞㻘㻢㻥㻠㻘㻣㻜㻜㻯㻙㻝㻝㻝㻞㻘㻣㻜㻜

㻺㼍㻙㻞㻞㻌

㻟㻜㻜㻯㼑㻙㻝㻟㻥㻌

㻝㻜㻺㼕㻙㻡㻣㻌

㻢㻘㻣㻜㻜㻯㼛㻙㻡㻢㻌

㻡㻜㻜㻼㼙㻙㻝㻠㻟㻌

㻟㻜㻜㻯㼛㻙㻡㻣㻌

㻝㻘㻝㻜㻣㻾㼎㻙㻤㻠㻌

㻞㻯㼛㻙㻡㻤㻌

㻤㻜㻜㻾㼎㻙㻤㻢㻌

㻡㻜㻜㻯㼛㻙㻢㻜㻌

㻟㻜㻜㻿㼎㻙㻝㻞㻠㻌

㻡㻜㻜㻯㼞㻙㻡㻝㻌

㻝㻜㻜㻿㼏㻙㻠㻢㻌

㻡㻘㻞㻜㻜㻯㼟㻙㻝㻟㻞㻌

㻞㻜㻜㻿㼞㻙㻤㻡㻌

㻢㻯㼟㻙㻝㻟㻢㻌

㻞㻘㻜㻜㻜㼀㼍㻙㻝㻤㻞㻌

㻡㻜㻜㻯㼡㻙㻢㻠㻌

㻝㻝㻜㻘㻜㻜㻜

㼀㼕㻙㻠㻠㻌

㻝㻯㼡㻙㻢㻣㻌

㻠㻘㻜㻜㻜

㼂㻙㻠㻤

㻟㻜㻜

㻲㻙㻝㻤

㻡㻘㻜㻜㻜

㼅㻙㻤㻤

㻠㻜

㻵㻙㻝㻞㻢

㻡㻜㻜

㼆㼚㻙㻢㻡㻌

㻠㻘㻝㻜㻜

㻷㻙㻠㻞

㻢㻘㻠㻜㻜

㼆㼞㻙㻥㻡㻌

㻞㻷㻙㻠㻟㻠㻞㻘㻜㻜㻜

全 㻟㻞 核種㻌

計 㻞㻘㻥㻜㻜㻘㻠㻣㻞㻌㼗㻮㼝㻌

134

IV. List of Publication

135

ELPH Annual Report, Tohoku University (2017)

List of Publication (論文リスト) (2017)

Papers Published in Refereed Journals
Demonstration of Coherent Radiation Generation up to 3THz from Femtosecond Electron Pulses
H. Hama, T. Abe, S. Kashiwagi, F. Hinode, T. Muto, H. Saito, K. Nanbu, K. Takahashi,
I. Nagasawa, K. Kanomata, H Saito, and Y. Saito
Int J Opt Photonics Eng, 2:004 (2017).
Study of Cherenkov Radiation from Thin Silica Aerogel
K. Nanbu, S. Kashiwagi, F. Hinode, T. Muto, I. Nagasawa, K. Takahashi, K. Kanomata,H. Saito, T. Abe, Y. Saito and H. Hama
Int J Opt Photonics Eng, 3:007 (2017).
Construction and commissioning of the compact energy-recovery linac at KEK
Mitsuo Akemoto, Dai Arakawa, Seiji Asaoka, Enrico Cenni, Masato Egi, Kazuhiro Enami,
Kuninori Endo, Shigeki Fukuda, Takaaki Furuya, Kaiichi Haga, Ryoichi Hajima,
Kazufumi Hara,

KentaroHarada,Tohru

Honda,

YosukeHonda,Teruya

Honma,

Kenji Hosoyama, Eiji Kako, Hiroaki Katagiri, Hiroshi Kawata, Yukinori Kobayashi,
Yuuji Kojima,

Yoshinari

Hiroshi Matsumura,

Kondou,HidekiOlga

Matsushita,

Tanaka,Tatsuya

Shinichiro

Kume,

Michizono,

Masao

Kuriki,TakakoMiura,

Tsukasa Miyajima, Shinya Nagahashi, Ryoji Nagai, Hirotaka Nakai, Hiromitsu Nakajima,
Norio

Nakamura,

Kota

Nakanishi,

Kazuyuki

Nigorikawa,Nobuyuki

Nishimori,Takashi Nogami, Shuichi Noguchi, Takashi Obina, Feng Qiu, Hidenori Sagehashi,
Hiroshi Sakai, Shogo Sakanaka, Shinichi Sasaki, Kotaro Satoh, Masaru Sawamura,
Miho Shimada, Kenji Shinoe, Toshio Shishido, Mikito Tadano, Takeshi Takahashi, Ryota Takai,Tateru Takenaka, Yasunori Tanimoto, Takashi Uchiyama, Akira Ueda, Kensei Umemori,
Ken Watanabe, Masahiro Yamamoto
Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers,
Detectors and Associated Equipment, 877 (2018), 197-219.
核理研から電子光センター、50 年の歩み
日出富士雄、濱 広幸
加速器、Vol. 14, No. 2 (2017) 74 – 80
ILC の多角的活用
岩下芳久、山本樹、河村成肇、牧村俊助、野村大輔、下村浩一郎、山崎高幸、柏木茂、

136

兵頭俊夫、三島賢二、早川岳人、嶋達志
加速器、Vol. 14, No.4 (2017) 236-242.
Prospoects for Electron Scattering on Unstable, Exotic Nuclei (Review paper)
T. Suda and H. Simon
Progress of Particle and Nuclear Physics, 96 (2017) 1-31.
First Elastic Electron Scattering from 132Xe at the SCRIT Facility
K. Tsukada, A. Enokizono, T. Ohnishi, K. Adachi, T. Fujita, M. Hara, M. Hori, T. Hori,
S. Ichikawa, K. Kurita, K. Matsuda, T. Suda, T. Tamae, M. Togasaki, M. Wakasugi,
M. Watanabe, and K. Yamada
Phys. Rev. Lett. 118 (2017) 262501.
陽子電荷半径パズル
須田利美
パリティー 33 (2018) 57-59.
極低運動量領域での電子・陽子弾性散乱による陽子荷電半径の精密決定
須田利美、塚田暁
原子核研究 61(2017) 87-98.
Use of different surface covering materials to enhance removal of radiocaesium in plants and upper soil
from orchards in Fukushima prefecture.
M. Sato, H. Akai, Y. Saito, T. Takase, H. Kikunaga,N. Sekiya, T. Ohtsuki, and K. Yamaguchi
Journal of Environmental Radioactivity (in press).
Neutral Kaon Spectrometer 2
M. Kaneta, B. Beckford, T. Fujii, Y. Fujii, K. Futatsukawa, Y.C. Han, O. Hashimoto, K. Hirose,
T. Ishikawa, H. Kanda, C. Kimura, K. Maeda, S.N. Nakamura, K. Suzuki, K. Tsukada,F. Yamamoto, H. Yamazaki
Nucl. Instrum. Meth. A886 (2018) 88-103
Beam helicity asymmetries in K+Λ electroproduction off the proton at low Q 2
P. Achenbach , C. Ayerbe Gayoso, R. Böhm, O. Borodina, D. Bosnar, V. Bozkurt, P. Bydžovský,L. Debenjak, M.O. Distler, A. Esser, I. Friščić, Y. Fujii, T. Gogami, M. Gómez Rodríguez,
O. Hashimoto, S. Hirose, H. Kanda, M. Kaneta, E. Kim, A. Margaryan, H. Merkel, U. Müller,
S. Nagao, S.N. Nakamura, J. Pochodzalla, C. Rappold, J. Reinhold, T.R. Saito,
A. Sanchez Lorente, S. Sánchez Majos, B.S. Schlimme, M. Schoth, F. Schulz, C. Sfienti,
S. Širca, D. Skoupil, L. Tang, M. Thiel, K. Tsukada
Eur. Phys. J. A53 (2017) no,10, 198
Spectroscopy of pionic atoms in 122Sn(d,3He) reaction and angular dependence of the formation crosssections

137

T. Nishi, K. Itahashi, G.P.A. Berg, H. Fujioka, N. Fukuda, N. Fukunishi, H. Geissel,
R.S. Hayano, S. Hirenzaki, K. Ichikawa, N. Ikeno, N. Inabe, S. Itoh, M. Iwasaki, D. Kameda,
S. Kawase, T. Kubo, K. Kusaka, H. Matsubara, S. Michimasa, K. Miki, G. Mishima, H. Miya,
H. Nagahiro, M. Nakamura, S. Noji, K. Okochi, S. Ota, N. Sakamoto, K. Suzuki, H. Takeda,
Y.K. Tanaka, K. Todoroki, K. Tsukada, T. Uesaka, Y.N. Watanabe, H. Weick, H. Yamakami,
K. Yoshida
Phys. Rev. Lett. Accepted
Oxygen-15 labeled CO2, O2, and CO PET in small animals: evaluation using a 3D-mode microPET
scanner and impact of reconstruction algorithms
Genki Horitsugi, Tadashi Watabe, Yasukazu Kanai, Hayato Ikeda, Hiroki Kato, Sadahiro Naka,
Mana Ishibashi, Keiko Matsunaga, Kayako Isohashi, Eku Shimosegawa, Jun Hatazawa
EJNMMI Research 7, (2017) 91.
First demonstration of multi-color 3-D in vivo imaging using ultra-compact Compton camera
Aya Kishimoto, Jun Kataoka, Takanori Taya, Leo Tagawa, Saku Mochizuki, Shinji Ohsuka,
Yuto Nagao, Keisuke Kurita, Mitsutaka Yamaguchi, Naoki Kawachi, Keiko Matsunaga,
Hayato Ikeda, Eku Shimosegawa, and Jun Hatazawa
Scientific Reports 7 (2017) 2110.
Practical calculation method to estimate the absolute boron concentration in tissues using 18F-FBPA PET
Tadashi Watabe; Kohei Hanaoka; Sadahiro Naka; Yasukazu Kanai; Hayato Ikeda;
Masanao Aoki; Eku Shimosegawa; Mitsunori Kirihata; Jun Hatazawa
Annals of Nuclear Medicine 31 (2017) 481–485.
Charge-to-time converting leading-edge discriminator for plastic-scintillator signals.
T. Ishikawa, Y. Takeda, Y. Honda, Y. Inoue, H. Kanda, S. Kido, Y. Matsumura, M. Miyabe,
I. Nagasawa, H. Shimizu, T. Takeda, A.O. Tokiyasu, Y. Tsuchikawa, H. Yamazaki
Nuclear Instruments and Methods in Physics Research Section A, 875(2017) 193-200
First measurement of coherent double neutral-pion photoproduction on the deuteron at incident energies
below 0.9 GeV.
T. Ishikawa, H. Fujimura, H. Fukasawa, R. Hashimoto, Q. He, Y. Honda, T. Iwata, S. Kaida,
H. Kanda, J. Kasagi, A. Kawano, S. Kuwasaki, K. Maeda, S. Masumoto, M. Miyabe,
F. Miyahara, K. Mochizuki, N. Muramatsu, A. Nakamura, K. Nawa, S. Ogushi, Y. Okada,K. Okamura, Y. Onodera, K. Ozawa, Y. Sakamoto, M. Sato, H. Shimizu, H. Sugai, K. Suzuki,
Y. Tajima, Y. Taniguchi, Y. Tsuchikawa, H. Yamazaki, R. Yamazaki, and H.Y. Yoshida
Physics Letters B, 772(2017) 398-402.
First Determination of the Level Structure of an sd-Shell Hypernucleus, 19ΛF
S.B. Yang et al.,Phys. Rev. Lett. 120 (2018) 132505(1-5)

138

Reopening of Research Activities on Strangeness Nuclear Physics at J-PARC
Kazuhiro Tanaka, Hirokazu Tamura,
Nucl. Phys. News 27 (2017) 21-27.
Missing-mass spectroscopy with the 6Li(π−,K+)X reaction to search for 6ΛH
R. Honda et al..
Phys. Rev. C96 (2017) 014005(1-23) (Editors’ Suggestion).
Identification of regions responsible for the function of the plant K+ channels KAT1 and AKT2 in
Saccharomyces cerevisiae and Xenopus laevis oocytes
Saito, S., Hoshi, N., Zulkifli, L., Widyastutib, S, Goshima, S., Dreyer, I. and Uozumi,
N. Channels, 510-516, 11 (6) (2017)
Dimerization of GTR1 regulates their plasmamembrane localization.
Ishimaru, Y., Washiyama, K. Oikawa, T. Hamamoto, S. Uozumi, N. and Ueda, M.
Plant Signal. Behav. e1334749, 12, (6) (2017)
Probing native metal ion association sites through quenching of fluorophores in the nucleotide binding
domains of the ABC transporter MsbA.
Tatsumi, D., Nanatani, K., Koike, Y., Kamagata, K., Takahashi, S., Konno, A., Furuta, T.,
Sakurai, M. and Uozumi, N.
Biochem. J. 474, 1993-2007 (2017)
Kup-mediated Cs+ uptake and Kdp-driven K+ uptake coordinate to promote cell growth during excess
Cs+ conditions in Escherichia coli
Tanudjaja, Ellen, Hoshi, N., Su, Y-S., Hamamoto, S. and Uozumi, N.
Sci. Rep. 7, 2122 (2017)
GTR1 is a jasmonic acid and jasmonoyl-l-isoleucine transporter in Arabidopsis thaliana.
Ishimaru, Y., Oikawa, T., Suzuki, T., Takeishi, S., Matsuura, H., Takahashi, K., Hamamoto, S.,
Uozumi, N., Shimizu, T., Seo, M., Ohta, H., and Ueda, M.
Biosci. Biotech. Biochem. 81, 249-255 (2017)
Gene expression analyses of the small intestine of pigs in the ex-evacuation zone of the Fukushima
Daiichi Nuclear Power Plant
Motoko Morimoto, Ayaka Kato, Jin Kobayashi, Kei Okuda, Yoshikazu Kuwahara,
Yasushi Kino, Yasuyuki Abe, Tsutomu Sekine, Tomokazu Fukuda, Emiko Isogai, Manabu
Fukumoto
BMC Veterinary Research, 13 (2017) 337.
Bound and resonance states of positronic copper atoms.
Takuma Yamashita, Muhammad Umair, Yasushi Kino
Journal of Physics B: Atomic, Molecular and Optical Physics 50 (2017) 205002.
Fusion hindrance for the positive Q-value system 12C+30Si

139

G. Montagnoli, A.M. Stefanini, C.L. Jiang, K. Hagino, F. Galtarossa, G. Colucci, S. Bottoni,
C. Broggini, A. Caciolli, P. Colovic, L. Corradi, S. Courtin, R. Depalo, E. Fioretto, G.Fruet,
A. Gal, A. Goasdu, M. Heine, S.P. Hu, M. Kaur, T. Mijatovic, M. Mazzocco, D. Montanari,
F. Scarlassara, E. Strano, S. Szilner, and G.X. Zhang,Phys. Rev. C, in press.
Determination of fusion barrier distributions from quasielastic scattering crosssections towards
superheavy nuclei synthesis
T. Tanaka, Y. Narikiyo, K. Morita, K. Fujita, D. Kaji, K. Morimoto, S. Yamaki,
Y. Wakabayashi, K. Tanaka, M. Takeyama, A. Yoneda, H. Haba, Y. Komori, S. Yanou,
B.J.-P. Gall, Z. Asfari, H. Faure, H. Hasebe, M. Huang, J. Kanaya, M. Murakami, A. Yoshida,
T. Yamaguchi, F. Tokanai, T. Yoshida, S. Yamamoto, Y. Yamano, K. Watanabe, S. Ishizawa,
M. Asai, R. Aono, S. Goto, K. Katori, and K. Hagino,
J. Phys. Soc. Jpn. 87 (2018) 014201/1-9.
Role of deformation in odd-even staggering in reaction cross sections for 30,31,32Ne and 36,37,38Mg isotopes
Y. Urata, K. Hagino, and H. Sagawa,Phys. Rev. C96 (2017) 064311/1-6.
Transition from vibrational to rotational characters in low-lying states of hypernuclei
H. Mei, K. Hagino, J.M. Yao, and T. Motoba,
Phys. Rev. C96 (2017) 014308/1-9.
Applicability of the Wong formula for fusion cross sections from light to heavy systems
N. W. Lwin, N. N. Htike, and K. Hagino,
Phys. Rev. C95 (2017) 064601/1-4.
New and efficient method for solving the eigenvalue problem for the two-center shell model with finite
depth potentials
K. Hagino and T. Ichikawa,Phys. Rev. C95 (2017) 054620/1-7.
Quantum tunneling with friction
M. Tokieda and K. Hagino,
Phys. Rev. C95 (2017) 054604/1-9.
書評量子散乱理論への招待；フェムトの世界を見る物理
萩野浩一
日本物理学会誌73(2018) 118-119.
 photoproduction on the proton at E=1.5-2.9 GeV
K. Mizutani, M. Niiyama, T. Nakano, M. Yosoi, Y. Nozawa, D.S. Ahn, J. K. Ahn, W.C. Chang,
J. Y. Chen, S. Daté, W. Gohn, H. Hamano, T. Hashimoto, K. Hicks, T. Hiraiwa, T. Hotta,
S.H. Hwang, T. Ishikawa, K. Joo, W.S. Jung, Y. Kato, H. Katsuragawa, M H. Kim, S.H. Kim,

140

H. Kohri, Y. Kon, H. S. Lee, Y. Maeda, Y. Matsumura, T. Mibe, M. Miyabe, Y. Morino,
N. Muramatsu, Y. Nakatsugawa, H. Noumi, Y. Ohashi, T. Ohta, M. Oka, J.B. Park, J.D. Parker,
C. Rangacharyulu, S. Y. Ryu, Y. Sada, T. Sawada, T. Shibukawa, S. H. Shiu, Y. Sugaya,
M. Sumihama, S. Tanaka, A.O. Tokiyasu, N. Tomida, H. N. Tran, T. Tsunemi, M. Uchida,
M. Ungaro, and Y. Yanai (LEPS Collaboration)
Physical Review C 96 (2017) 062201(R).
Differential cross section and photon-beam asymmetry for the p→+n reaction at forward + angles at
E=1.5-2.95 GeV
H. Kohri, S. Y. Wang, S.H. Shiu, W.C. Chang, Y. Yanai, D.S. Ahn, J.K. Ahn, J.Y. Chen,
S. Daté, H. Ejiri, H. Fujimura, M. Fujiwara, S. Fukui, W. Gohn, K. Hicks, A. Hosaka, T. Hotta,
S.H. Hwang, K. Imai, T. Ishikawa, K. Joo, Y. Kato, S.H. Kim, Y. Kon, H.S. Lee, Y. Maeda,
T. Mibe, M. Miyabe, Y. Morino, N. Muramatsu, T. Nakano, Y. Nakatsugawa, M. Niiyama,
H. Noumi, Y. Ohashi, T. Ohta, M. Oka, J. D. Parker, C. Rangacharyulu, S.Y. Ryu, T. Sawada,
H. Shimizu, Y. Sugaya, M. Sumihama, T. Tsunemi, M. Uchida, M. Ungaro, and M. Yosoi(LEPSCollaboration)
Physical Review C 97 (2018) 015205.
Photoproduction of  and 0 hyperons with linearly polarized photons at E=1.5-3.0 GeV
S.H. Shiu, H. Kohri, W.C. Chang, D.S. Ahn, J.K. Ahn, J.Y. Chen, S. Daté, H. Ejiri,
H. Fujimura, M. Fujiwara, S. Fukui, W. Gohn, K. Hicks, T. Hotta, S.H. Hwang, K. Imai,
T. Ishikawa, K. Joo, Y. Kato, Y. Kon, H.S. Lee, Y. Maeda, T. Mibe, M. Miyabe, K. Mizutani,
Y. Morino, N. Muramatsu, T. Nakano, Y. Nakatsugawa, M. Niiyama, H. Noumi, Y. Ohashi,
T. Ohta, M. Oka, J.D. Parker, C. Rangacharyulu, S.Y. Ryu, T. Sawada, H. Shimizu, Y. Sugaya,
M. Sumihama, T. Tsunemi, M. Uchida, M. Ungaro, and M. Yosoi (LEPS Collaboration)
Physical Review C 97 (2018) 015208.
A study of event mixing for two-pion Bose-Einstein correlations in the p→00p㻌 reaction
Q. He, J. Ai, T. Ishikawa, T. Li, L. Ma, J. Ma, M. Miyabe, N. Muramatsu, H. Shimizu,
Y. Tsuchikawa, Y. Xiang, H. Yamazaki, Y. Zhang
Progress of Theoretical and Experimental Physics 2017-3 (2017) 033D02.
Low-energy eta-nucleon interaction studied with eta photoproduction off the deuteron
S.X. Nakamura, H. Kamano, T. Ishikawa
Physical Review C 96, 042201 (R) (2017).
ダークマターの正体に迫る
協力 森山茂栄／小川 泉／時安敦史／鳥居祥二／浅井祥仁
執筆 福田伊佐央（編集部）
Newton 10 月号 解説記事
Design and performance of the spin asymmetries of the nucleon experiment

141

J.D.Maxwell et al. (SANE collaboration), (SNN 80 of 105),
Nucl. Inst. and Meth. A 885 (2018) 145-159.
Virtual Institute for Quark Nuclear Physics at SPring-8/LEPS2
H. Shimizu and N. Muramatsu,
Nuclear Physics News 27:1 (2017) 19-22.
Replication Experiments at Tohoku University on Anomalous Heat Generation Using Nickel-Based
Binary Nanocomposites and Hydrogen Isotope Gas
Y. Iwamura, T. Itoh, J. Kasagi, A. Kitamura, A. Takahashi and K. Takahashi
J. Condensed Matter Nucl. Sci. 24 (2017) 191–201.
Anomalous Excess Heat Generated by the Interaction between Nano-structured Pd/Ni surface and D2/H2
gas
T. Itoh, Y. Iwamura, J. Kasagi and H. Shishido
J. Condensed Matter Nucl. Sci. 24 (2017) 179–190.
Collaborative Examination on Anomalous Heat Effect Using Nickel-based Binary Nanocomposites
Supported by Zirconia
A. Kitamura, A. Takahashi, K. Takahashi, R. Seto, Y. Matsuda, Y. Iwamura, T. Itoh, J. Kasagi,
M. Nakamura, M. Uchimura, H. Takahashi, T. Hioki, T. Motohiro, Y. Furuyama andM. Kishida
J. Condensed Matter Nucl. Sci. 24 (2017) 202–213.
【クローズアップ】凝縮系核反応の現状と今後の発展
岩村康弘
パリティ, Vol32, No.05, p.44-49, 2017.

Papers Published in International Conference Proceedings
Observation of Coherent Undulator Radiation in THz Region
S. Kashiwagi, H. Saito, F. Hinode, K. Kanomata, S. Miura, T. Muto, I. Nagasawa, N. Nishimori,K. Nanbu, Y. Saito, K. Takahashi and H. Hama
Infrared Physics and Tech. (in press).
Numerical Study of Cherenkov Radiation from Thin Silica Aerogel
H. Hama, K. Nanbu, H. Saito, Y. Saito
Proc. 38th Int. Free Electron Laser Conf., Santa Fe, NM, 471 – 473 (2017).
Measurement of Pionic 121Sn atoms at the RI beam factory
Kenta Itahashi, Georg P.A. Berg, Hiroyuki Fujioka, Hans Geissel, Ryugo S. Hayano,
Satoru Hirenzaki,

NatsumiIkeno,

NaohitoInabe,

SatoshiItoh,

Daisuke

Kameda,Toshiyuki Kubo, Hiroaki Matsubara, Shinichiro Michimasa, Kenjiro Miki, Hiroyuki Miya,

142

Masaki Nakamura, Takahiro Nishi, Shumpei Noji, Shinsuke Ota, Ken Suzuki, Hiroyuki Takeda,
Koichi Todoroki, Kyo Tsukada, Tomohiro Uesaka, Helmut Weick, Koichi Yoshida
Proceedings, 4th International Conference on Exotic Atoms and Related Topics (EXA 2011) :Vienna, Austria, September 5-9, 2011
Spectroscopic Study of Hyperon Resonance Below KbarN Threshold via the d(K −,n) Reaction
K. Inoue, S. Ajimura, G. Beer, H. Bhang, M. Bragadireanu, P. Buehler, L. Busso, M. Cargnelli,
S. Choi, C. Curceanu, S. Enomoto, D. Faso, H. Fujioka,Y. Fujiwara, T. Fukuda, C. Guaraldo,
T. Hashimoto, R. S. Hayano, T. Hiraiwa, M. Iio, M. Iliescu, Y. Ishiguro, T. Ishikawa,
S. Ishimoto, T. Ishiwatari, K. Itahashi, M. Iwai, M. Iwasaki, Y. Kato, S. Kawasaki, P. Kienle,
H. Kou, Y. Ma, J. Marton, Y. Matsuda, Y. Mizoi O. Morra, T. Nagae, H, Noumi,H. Ohnishi,
S. Okada, H. Outa, K. Piscicchia, M. Poli Lener, A. Romero Vidal, Y. Sada, A. Sakaguchi,
F. Sakuma, M. Sato, A. Scorde, M. Sekimoto, H. Shi, K. Shirotori, D. Sirghi, F. Sirghi,
K. Suzuki, S. Suzuki, T. Suzuki, K. Tanida, H. Tatsuno, M. Tokuda, D. Tomono, A. Toyoda,
K. Tsukada, O. Vazquez Doce, E. Widmann, B. K. Wuenschek, T. Yamaga, T. Yamazaki,
H. Yim, Q. Zhang, and J. Zmeskal
JPS Conf.Proc. 17 (2017) 072003
High-Resolution Decay-Pion Spectroscopy of 4ΛH Hypernuclei
P. Achenbach, F. Schulz, S. Nagao, S. Aulenbacher, J. Beričič, S. Bleser, R. Böhm, D. Bosnar,
L. Correa, M. O. Distler, A. Esser, H. Fonvieille, I. Friščić, Y. Fujii, M. Fujita, T. Gogami,
H. Kanda, M. Kaneta, S. Kegel, Y. Kohl, W. Kusaka, A. Margaryan, H. Merkel,
M. Mihovilovič, U. Müller, S. N. Nakamura, J. Pochodzalla, A. Sanchez Lorente,
B. S. Schlimme, M. Schoth, C. Sfienti, S. Širca, M. Steinen, Y. Takahashi, L. Tang, M. Thiel,
K. Tsukada, A. Tyukin, and A. Weber
JPS Conf. Proc. 17, 011001 (2017).
The Recent Results of Strangeness Photoproduction in the Threshold Region at ELPH-Tohoku
Hiroki Kanda, Brian Beckford, Petr Bydžovský, Takeji Fujibayashi, Takao Fujii, Yu Fujii,
Kenta Futatsukawa, Toshiyuki Gogami, Yun-Cheng Han, Osamu Hashimoto, Kentaro Hirose,
Kenji Hosomi, Ryotaro Honda, Alan Iguchi, Takatsugu Ishikawa, Masashi Kaneta,
Yusuke Kaneko, Yuma Kasai, Taito Kawasaki, Chigusa Kimura, Shogo Kiyokawa,Takeshi Koike, Kazushige Maeda, Nayuta Maruyama, Masao Matsubara, Koji Miwa,
Yohei Miyagi, Sho Nagao, Satoshi N. Nakamura, Takashi Nishizawa, Akira Okuyama,
Miloslav Sotona, Tadaaki Tamae, Hirokazu Tamura, Kyo Tsukada, Nobu Terada, Mifuyu Ukai,
Tie-Shan Wang, Fumiya Yamamoto, Takeshi O. Yamamoto, and Hirohito Yamazaki
JPS Conf. Proc. 17 (2017) 062006(1-4)
The Performance Of The Scrit Detectors For Electron-RI Scattering Experiment

143

Akitomo Enokizono, Kousuke Adachi, Takahiro Fujita, Masahiro Hara, Mitsuki Hori,
Toshitada Hori, Sin'Ichi Ichikawa, Keita Kasama, Kazuyoshi Kurita, Kazuki Namba,
Tatsuya Ohnishi, Shin-Nosuke Sasamura, Toshimi Suda, Tadaaki Tamae, Kyo Tsukada,
Mamoru Togasaki, Nobuaki Uchida, Masanori Wakasugi, Shou Wang, Masamitsu Watanabe,
Kouhei Yamada
Proceedings, 26th International Nuclear Physics Conference (INPC2016) :Adelaide, Australia,
September 11-16, 2016
The Scrit Electron Scattering Facility At Riken RI Beam Factory
Tetsuya Ohnishi, Masahiro Hara, Toshitada Hori, Shinichi Ichikawa, Masamitu Watanabe,
Masanori Wakasugi, Kosuke Adachi, Akitomo Enokizono, Takahiro Fujita, Mitsuki Hori,
Shinnosuke Sasamura, Mamoru Togasaki, Nobuaki Uchida, Kouhei Yamada, Kazuyoshi Kurita,
Keita Kasama, Kazuki Namba, Kyo Tsukada, Tadaaki Tamae, Toshimi Suda, Shuo Wang,
Takashi Kikuchi
Proceedings, 26th International Nuclear Physics Conference (INPC2016) : Adelaide, Australia,
September 11-16, 2016
First Result from Scrit Electron Scattering Facility : Charge Density Distribution Of 132Xe
Kyo Tsukada, Keita Kasama, Kazuki Namba, Toshimi Suda, Tadaaki Tamae, Masahiro Hara,
Shinnichi

Ichikawa,

TetsuyaOhnishi,

Masanori

Wakasugi,

Masamitsu

Watanabe,

Kousuke Adachi, Akitomo Enokizono, Toshihiro Fujita, Mitsuki Hori, Kazuyoshi Kurita,
Shinnosuke Sasamura, Mamoru Togasaki, Nobuaki Uchida, Kouhei Yamada
Proceedings, 26th International Nuclear Physics Conference (INPC2016) : Adelaide, Australia,
September 11-16, 2016
Low-energy Scattering Parameters Between the eta Meson and Nucleon from eta Photoproduction on theDeuteron
T. Ishikawa, K. Aoki, H. Fujioka, Y. Honda, T. Hotta, Y. Inoue, K. Itahashi, H. Kanda,
H. Kawai, K. Maeda, Y. Matsumura, M. Miyabe, S. Miyata, N. Muramatsu, T. Nishi,
H. Ohnishi, K. Ozawa, H. Shimizu, R. Shirai, M. Tabata, A.O. Tokiyasu, Y. Tsuchikawa, andH. Yamazaki
ACTA PHYSICA POLONICA B, 48(2017) 1801-1806.
Search For A Ξ Bound State In The 12C(K−,K+)X Reaction At 1.8 GeV/c in J-PARC
Tomofumi Nagae et al..
PoS INPC2016 (2017) 038-44
Spectroscopy of Nuclei with Multi-Strangeness by Using New S-2S Spectrometer at J-PARC
Toshiyuki Gogami et al..
JPS Conf. Proc. 18 (2017) 011031(1-6)
The First Gamma-ray Spectroscopic Study of sd-shell Hypernucleus, 19ΛF

144

S.B. Yang et al..
JPS Conf. Proc. 17 (2017) 012004(1-4)
High Statistics Σp Scattering Experiment Using High Intensity Pion Beams at J-PARC
K. Miwa et al..
JPS Conf. Proc. 17 (2017) 041002(1-6)
Search for Excited State of Σ Hypernucleus in the J-PARC E13 Experiment
M. Nakagawa et al..
JPS Conf. Proc. 17 (2017) 012009(1-4)
Gamma-ray Spectroscopy of Hypernuclei — Recent Results and Prospect at J-PARC —H. Tamura et al.,JPS Conf. Proc. 17 (2017) 011004(1-11)
Time course change of radiocesium concentration in wild mushrooms collected in Miyagi prefecture,
Japan from 2011 to 2014
A. Irisawa, Y. Kino,
Proceedings of the 4th International Conference on Environmental Radioactivity
ENVIRA2017, (2017) 29-32.
A coupled rearrangement channel analysis of positronium antihydride
Takuma Yamashita, Yasushi Kino, Emiko Hiyama, Svante Jonsell, Piotr Froelich,
Journal of Physics, Conference Series, 875 (2017) 052031
Degradation of electron-irradiated polyethylene studied by positron annihilation lifetime spectroscopy
Karin Onodera, Toshitaka Oka, Yasushi Kino, Tsutomu Sekine,
Journal of Physics: Conference Series, 791 (2017) 012026
Uptake of Radioactive Cesium by Intestinal and Probiotic Bacteria
K. Saito, K. Kuroda, T. Sekine, M. Fukumoto, Y. Kino, T. Fukuda, H. Yamashiro, H. Shinoda,
H. Isogai, J. Kobayashi, J. Nishimura, Y. Abe, N. Nishida, M. Kouno, E. Isogai,
Journal of Integrated Field Science, 14 (2017) 111.
Evolving theoretical descriptions of heavy-ion fusion: from phenomenological to microscopic approaches
K. Hagino
EPJ Web of Conf. 163 (2017) 00022/1-6.
Three-body model for nuclei near and beyond drip line
H. Sagawa and K. Hagino,
Acta Phys. Polon. Supp. 10 (2017) 211-224.
Description of multi-nucleon transfer and fusion reactions with the coupled-channel method
G. Scamps, D. Bourgin, F. Haas, K. Hagino, and S. Courtin,
PoS INPC2016 (2017) 213/1-7.
Beyond-mean-field approach to low-lying spectra of  hypernuclei

145

K. Hagino, H. Mei, J.M. Yao, and T. Motoba,
JPS Conf. Proc. 17 (2017) 012007/1-4.
Kaonic-Atom X-ray Spectroscopy with Superconducting Microcalorimeters
T. Hashimoto, M. Bazzi, D.A. Bennett, C. Berucci, D. Bosnar, C. Curceanu, W.B. Doriese,
J.W. Fowler, H. Fujioka, C. Guaraldo, F. Parnefjord Gustafsson, R.S. Hayano,
J.P. Hays-Wehle, G.C. Hilton, T. Hiraiwa, M. Iio, M. Iliescu, S. Ishimoto, K. Itahashi,
M. Iwasaki, Y. Ma, H. Noumi, G.C. O’Neil, H. Ohnishi, S. Okada, H. Outa, K. Piscicchia,
C.D. Reintsema, Y. Sada, F. Sakuma, M. Sato, D.R. Schmidt, A. Scordo, M. Sekimoto, H. Shi,
D. Sirghi, F. Sirghi, K. Suzuki, D.S. Swetz, K. Tanida, H. Tatsuno, M. Tokuda, J. Uhlig,
J.N. Ullom, S. Yamada, T. Yamazaki, and J. Zmeskal
JPS Conf. Proc. 17, 072001 (2017)
Probing Strong Interaction with Kaonic Atoms – from DANE to J-PARC
J. Zmeskal, M. Sato, M. Bazzi, G. Beer, C. Berucci, D. Bosnar, M. Bragadireanu, P. Buehler,
M. Cargnelli, A. Clozza, C. Curceanu, A. D'uffizi, L. Fabbietti, C. Fiorini, F. Ghio, R. Golser,
C. Guaraldo, T. Hashimoto, R.S. Hayano, M. Iliescu, K. Itahashi, M. Iwasaki, P. Levi Sandri,
J. Marton, P. Moskal, H. Ohnishi, S. Okada, H. Outa, D. Pietreanu, K. Piscicchia, . Poli Lener,
A. Romero Vidal, F. Sakuma, E. Sbardella, A. Scordo, H. Shi, D. Sirghi, F. Sirghi, K. Suzuki,
I. Tucakovic, O. Vazquez Doce, E. Widmann
JPS Conf.Proc. 17 (2017) 071001
Spectroscopic Experiment of (1405) via the In-flight d(K−, n) Reaction at J-PARC K1.8BR
S. Kawasaki, S. Ajimura, G. Beer, H. Bhang, M. Bragadireanu, P. Buehler, L. Busso,
M. Cargnelli, S. Choi, C. Curceanu, S. Enomoto, D. Faso, H. Fujioka, Y. Fujiwara, T. Fukuda,
C. Guaraldo, T. Hashimoto, R. Hayano, T. Hiraiwa, M. Iio, M. Iliescu, K. Inoue, T. Ishikawa,
S. Ishimoto, K. Itahashi, M. Iwai, M. Iwasaki, P. Kienlep, H. Kou, Y. Ma, J. Marton,Y. Matsuda, H. Mizoi, O. Morra, T. Nagae, H. Noumi, H. Ohnishi, S. Okada, H. Outa,
D. Pietreanu, Y. Sada, A. Sakaguchi, F. Sakuma, M. Sato, M. Sekimoto, H. Shi, K. Shirotori,
D. Sirghi, F. Sirghi, K. Suzuki, S. Suzuki, T. Suzuki, K. Tanida, H. Tatsuno, M. Tokuda,
M. Tomono, A. Toyoda, K. Tsukada, E. Widmann, T. Yamaga, K. Yoshida, T. Yamazaki,
H. Yim, Q. Zhang, J. Zmeskal
JPS Conf.Proc. 13 (2017) 020018
Study of non-strange dibaryon resonances via coherent double neutral-pion photoproduction on the
deuteron
Takatsugu Ishikawa, Hisako Fujimura, Ryo Hashimoto, Qinghua He, Shun Kaida,
Manabu Miyabe, Norihito Muramatsu, Hajime Shimizu, Koutaku Suzuki, Yusuke Tschikawa,
Hirohito Yamazaki, Shin'ichi Masumoto, Hiroki Kanda, Kazushige Maeda, Kyoichiro Ozawa.
PoS(Hadron2017)065 (2018).

146

Low-energy scattering parameters between the eta meson and nucleon from eta photoproduction on the
deuteron
T. Ishikawa, K. Aoki, H. Fujioka, Y. Honda, T. Hotta, Y. Inoue, K. Itahashi, H. Kanda,
H. Kawai, K. Maeda, Y. Matsumura, M. Miyabe, S. Miyata, N. Muramatsu, T. Nishi,
H. Ohnishi, K. Ozawa, H. Shimizu, R. Shirai, M. Tabata, A.O. Tokiyasu, Y. Tsuchikawa,
H. Yamazaki
Acta Physica Polonica B48, 1801 (2017).
Study of  Invariant Mass Spectrum in the d(,K+)X Reaction
Atsushi Tokiyasu for the LEPS collaboration
JPS Conf.Proc. 17 (2017) 082002
n Scattering Length from the d→pn Reaction at E0.9 GeV
Takatsugu Ishikawa, Hiroyuki Fujioka, Yuki Honda, Tomoaki Hotta, Yosuke Inoue,
Kenta Itahashi, Hiroki Kanda, Hideyuki Kawai, Kazushige Maeda, Manabu Miyabe,
Seiya Miyata, Yuji Matsumura, Norihito Muramatsu, Hiroaki Ohnishi, Kyoichiro Ozawa,
Mizuki Sasagawa, Hajime Shimizu, Ken'ichiro Shiraishi, Makoto Tabata, Atsushi O Tokiyasu,
Yusuke Tsuchikawa
JPS Conf.Proc. 13 (2017) 020031
Study of the d(γ,K+)ΣπN Reaction at LEPS
Atsushi Tokiyasu for the LEPS collaboration
JPS Conf.Proc. 13 (2017) 020017
Spectroscopic Study of Λ Hypernuclei with Electron Beams at Jefferson Lab
Satoshi N. Nakamura, Toshiyuki Gogami and Liguang Tang,JPS Conf. Proc. 17, 011002 (2017).
Study of −n Interaction via FSI in γ+d Reaction
Masashi Kaneta for the NKS2 collaboration
JPS Conference Proceedings 17 (2017) 062002-1 - 062002-4
Photoproduction of ' mesons at SPring-8/LEPS2
H. Shimizu
Acta Phys. Pol. B48 (2017) 1819-1824.
Anomalous Excess Heat Generated by the Interaction between Nano-structured Pd/Ni surface and D2 gas
T. Itoh, Y. Iwamura, J. Kasagi and H. Shisido
Proceedings of ICCF20,2-7 Oct 2016,Sendai, Japan, p.60-70
Observation of 141Pr by 40Ar Scattering (RBS) on Cs Implanted Pd/CaO multilayer foil with D2 Gas
Permeation
J. Kasagi, R. Tajima, Y. Honda, T. Itoh, Y. Iwamura, H. Kikunaga, and S. Tsuruga

147

Proceedings of the 20th International Conference on Condensed Matter Nuclear Science,
pp.160-165.

Invited Talk and Oral Presentations at International Conferences
SLiT-J, a project of high brilliant compact 3 GeV light source in Japan (Invited oral presentation)
Hiroyuki Hama
Diamond light source, Oxford, UK, Nov. 16, 2017.
SLiT-J, a project of high brilliant compact 3 GeV light source in Japan (Invited oral presentation)
Hiroyuki Hama
ALBA light source, Barcelona, Spain, Nov. 14, 2017.
Smith-Purcell FEL (Oral presentation)
Hiroyuki Hama
National Electronics and Computer Technology Center, Khlong Luang, Pathum Thani,
Thailand, Dec. 26, 2017.
ELPH present status (Oral presentation)
Hiroyuki Hama
Scandinova Systems, Uppsala, Sweden, Mar. 12, 2018.
Observation of coherent undulator radiation in THz region (Oral presentation)
S. Kashiwagi, H. Saito, F. Hinode, K. Kanomata, S. Miura, T. Muto, I. Nagasawa,
N. Nishimori, K. Nanbu, Y. Saito, K. Takahashi and H. Hama.
The 9th International Workshop on Infrared Microscopy and Spectroscopy with㻌 Accelerator
Based Sources, WIRMS 2017 25-28 September, 2017 Worcester College, Oxford UK
Coherent Undulator Radiation from Extremely Short Electron Bunches (Basic course) (Lecture)
Radioactive Isotope Production via Photo Nuclear Reaction using High Power Electron Linac(Application) (Lecture)
Shigeru Kashiwagi
日本インド加速器スクール (International School on Electron Accelerators, Free Electron
Laser and Application of electron beam/THz Radiation 2018), Inter University Accelerator
Centre (IUAC), New Delhi, India, 03-06 March 2018
Bunch length measurement system for ultra-short electron bunch using Cherenkov radiation (Oralpresentation)
Fujio Hinode
3rd International workshop on CSR and free electron lasers from ultra-short bunch㻌 electron
beam, Hefei, China, 3/13-14, 2018
Overview of SLiT-J Proposal – a high brilliant compact 3GeV light source project – (Oral presentation)
Nobuyuki Nishimori

148

Meeting on TPS and SLiT-J Projects, NSRRC Hsinchu, Taiwan, Feb. 14, 2017.
Commission results of the compact ERL high voltage DC gun (Invited oral presentation)
Nobuyuki Nishimori
The 59th ICFA Advanced Beam Dynamics Workshop on Energy Recovery Linacs, CERN
Geneva, Switzerland, Jun. 21, 2017.
Development of a multialkali photocathode DC gun for high current operation (Oral presentation)
Nobuyuki Nishimori
The 59th ICFA Advanced Beam Dynamics Workshop on Energy Recovery Linacs, CERN
Geneva, Switzerland, Jun. 22, 2017.
Development of a multialkali photocathode DC gun for a Smith-Purcell THz FEL (Oral presentation)
Nobuyuki Nishimori
2nd International workshop on CSR and free electron lasers from ultra short bunch electron
beam, ELPH Sendai, Japan, Sep. 20, 2017.
A Study of Generation of Variable Polarized THz Superradiance Using a Crossed Undulator (Oralpresentation)
Hirotoshi Saito
2nd International workshop on CSR and free electron lasers from ultra short bunch electron
beam (ELPH, Tohoku University), 20 September 2017.
Sub-picosecond bunch length measurement using Cherenkov radiation from a thin silica-aerogel (Oralpresentation)
Yuki Saito
2nd International workshop on CSR and free electron lasers from ultra short bunch electron
beam (ELPH, Tohoku University), 20 September 2017.
Study on Generation of Variable Polarized Coherent THz Radiation Using a Crossed Undulator (Oralpresentation)
Hirotoshi Saito
International workshop on CSR and FELs from ultra-short bunch electron beams (NSRL,
Hefei), 13 March 2018.
Electron Scattering Activities in Japan (Oral presentation)
T. SudaRAON シンポジウム、Daejon、Korea 2017 年 3 月 7 日
Electron scattering for neutron-rich exotic nuclei (Invited oral presentation)
T. SudaECT*研究会 “Walk on the neutron-rich side”, Trento, Italy, ２０１７年４月１３日
Probing two-nucleon system in nuclei and electron scattering off exotic nuclei (Invited oral presentation)
T. Suda149

QFS workshop、ヨーク大学、イギリス 2917 年 7 月 24 日
The SCRIT Electron Scattering Facility (Invited oral presentation)
T. SudaISPUN 国際シンポジウム、ハーロン、ベトナム、2017 年 9 月 25 日―10 月 1 日
Proton Charge Radius by electron scattering under the lowest-ever momentum transfer (Invited oralpresentation)
T. SudaFPU 国際会議、名古屋大学、名古屋市、２０１８年１月８―９日
Proton Radius Measurement in ELPH (Invited oral presentation)
T. SudaInternational Symposium on Nucleon Structure, 山形大学、山形、2018 年 3 月 8 日
RI production at ELPH (Invited oral presentation)
H. Kikunaga
The 7th Yamada Workshop on RI Science Evolution 2018 (RISE18), Osaka, 3/16-17, 2018
First result from SCRIT electron scattering facility with 132Xe target (Invited oral presentation)
K. Tsukada
The 10th International Conference on Nuclear Physics at Storage Rings、
金沢２０１７年１１月１３日－１８日
Proton radius puzzle at ELPH (Oral presentation)
Y. Honda
The 15th g-2/EDM collaboration meeting, Kyushu University, 2017 年 12 月 11-14
Hadrons in medium (Invited oral presentation)
H. TamuraThe 21st Particle and Nuclei International Conference (PANIC2017), 2017.9.1～9.5, Beijing,
China.
Experimental studies of high density baryonic matter with and without strangeness (Invited oralpresentation)
H. Tamura
XVII International Conference on Hadron Spectroscopy and Structure (Hadron2017), 2017. 9.
25～9.29, Salamanca, Spain.
Prospect for Hypernuclear Studies at J-PARC K1.1 Beam Line (Prospect on S= −1 Hypernuclei) (Invitedoral presentation)
H. Tamura“Advances and open problems in low-energy nuclear and hadronic STRAngeness physics”
workshop 2017.10.23-10.27, Trento, Italy.
Hypernuclear physics with kaon (and pion) beams (Invited oral presentation)

150

H. TamuraThe 2nd EMMI workshop: Anti-matter, hyper-matter, and exotica production at the LHC,2017.11.6~10, Torino, Italy.
Nuclear Physics with Strangeness (Invited oral presentation)
H. Tamura
56th International Winter Meeting on Nuclear Physics, 2018.1.22 ~ 1.26, Bormio, Italy.
Properties and behavior of baryons in a nucleus studied from precise gamma-spectroscopy and weak
decays of Λ hypernuclei
H. TamuraInternational Workshop on the Project for the Extended hadron Experimental Facility at
J-PARC 2018.3.26~28, KEK Tokai Campus, Tokai, Japan.
Nuclear reaction in atomic collision under a screening effect from negatively charged massive particle(Invited oral presentation)
Y.Kino,13th International Conference of Computational Methods in Science and Engineering, April
21-25, 2017, Thessaloniki, Greece.
Time course change of radiocesium concentration in wild mushrooms collected in Miyagi prefecture,
Japan from 2011 to 2014 (Oral presentation)
Y. Kino,Proceedings of the 4th International Conference on Environmental Radioactivity
ENVIRA2017, May29-June 2, 2017.
Nuclear reaction in muon atomic collision (Oral presentation)
Yasushi Kino,
The 30th International Conference on Photonic, Electronic and Atomic Collisions (ICPEAC
XXX), Cairns, Australia, 2017/7/26-8/1.
Fusion barrier distributions for superheavy elements (Invited oral presentation)
K. Hagino.
International Symposium on Physics of Unstable Nuclei 2017 (ISPUN17), Halong City,
Vietnam, September 25-30, 2017.
Three-body approach to unbound nuclei (Invited oral presentation)
K. Hagino
IIRC Symposium on Perspectives of the physics of nuclear structure, Tokyo, Japan, November
1-4, 2017.
Capture barrier distributions and superheavy elements (Invited Oral Presentation)
K. Hagino151

International Symposium on RI beam physics in the 21st century: 10th anniversary of RIBF,
December 4-5, 2017.
Heavy-ion fusion reactions and superheavy elements (Invited oral presentation)
K. Hagino
YITP school on “Recent Progress of Nuclear Structure and Reaction Physics”, Yukawa
Institute for Theoretical Physics, Kyoto University, December 18-22, 2017.
Search for  meson bound states (Invited oral presentation)
H. Ohnishi
XVII INTERNATIONAL CONFERENCE ON HADRON SPECTROSCOPY AND
STRUCTURE (2017), Salamanca, Spain, September 25th-29th 2017.
Non-strange dibaryons from photoproduction experiments at ELPH (Invited oral presentation)
T. Ishikawa
2017 JAEA/ASRC Reimei Workshop: Hadronic Resonances and Dense Nuclear Matter,
Ibaraki Quantum Beam Research Center (IQBRC), Tokai, Japan, December 11-13, 2017.
Study of non-strange dibaryon resonances via coherent double neutral-pion photoproduction on the
deuteron (Oral presentation)
T. Ishikawa
XVII International Conference on Hadron Spectroscopy and Structure, Salamanca, Spain,
September 25-29, 2017.
Low-energy scattering parameters between the eta meson and nucleon from eta photoproduction on the
deuteron (Invited oral presentation)
T. Ishikawa
2nd Jagiellonian Symposium of Fundamental and Applied Subatomic Physics, Collegium
Maius, Jagiellonian University Kraków, Poland, 4-9 June, 2017.
Study of Hypernuclei with Electron Beams (Invited oral presentation)
S. Nakamura
Gordon Research Conference, Nuclear Chemistry, New London NH USA, 8-23 June 2017.
Results from the hypernuclear physics experiment at JLab and future perspectives (Invited oralpresentation)
S. Nakamura
XVII International Conference on Hadron Spectroscopy and Structure (HADRON2017),
Salamanca, Spain, 25th-29th Sep 2017.
An experimental approach to the hypertriton puzzle with hypernuclear (electro-)photo production (Oralpresentation)
S. Nagao and S.N. Nakamura

152

Advances and open problems in low-energy nuclear and hadronic STRAngeness physics(ASTRA), ECT*, Trento Italy, 23-27 Oct. 2017.
Electro-photo production of  hypernuclei and perspectives (Invited oral presentation)
S. Nakamura
2nd EMMI Workshop, Anti-matter, hyper-matter and exotica production at LHC, Turin Italy,
6-10 Nov. 2017
Photoproduction of ' mesons at SPring-8/LEPS2 (Invited oral presentation)
H. Shimizu
2nd Jagiellonian Symposium, Krakow, June 4-10, 2017.
Anomalous Heat Generation Experiments Using Metal Nanocomposites and Hydrogen Isotope Gas (Oralpresentation)
Y. Iwamura
12th International Workshop on Anomalies in Hydrogen Loaded Metals, Costigliole d'Asti(AT), Italy. 5-9 June 2017.
Anomalous Excess Heat Generation by the Interaction between Nano-structured Pd/Ni surface and D2/H2
gas (Oral presentation)
Y. Iwamura
12th International Workshop on Anomalies in Hydrogen Loaded Metals, Costigliole d'Asti(AT), Italy. 5-9 June 2017.
Recent Progress on Transmutation Experiments induced by D 2 gas permeation (Oral presentation)
T.Itoh, J. Kasagi, Y.Iwamura, S.Tsuruga
12th International Workshop on Anomalies in Hydrogen Loaded Metals, Asti, Italy, 5-9 June2017

学位論文（電子光理学研究センター所属）
修士論文「光生成反応による中間子核子間相互作用の決定精度の評価」
  笹川瑞貴平成  年度東北大学
修士論文「低屈折率シリカエアロゲル薄膜からのチェレンコフ光を用いたサブピコ秒バンチ長計測」
  齊藤悠樹平成  年度東北大学
修士論文「光生成による核子共鳴探索実験のための光子ビーム形状測定」
  白井凜太郎平成  年度東北大学

学位論文（他機関所属）
修士論文「G→G+−反応によるダイバリオンの探索」
  室井佑太平成  年度東北大学

153

修士論文「ハイパー核電磁分光実験のためのセプタム磁石の設計―11 相互作用のアイソス
ピン依存性の解明に向けて―」
  相田元気平成  年度東北大学
修士論文「Q 終状態相互作用研究に向けた 0XOWLJDSV5HVLVWLYH3ODWH&KDPEHU の開発」
  竹内大貴平成  年度東北大学
修士論文「シロイヌナズナの 1D 輸送体 $W+.7 の機能解析」
  竹林昂亮平成  年度東北大学

154

V. Members of Committees

155

Steering Committee
2017

Hiroyuki HAMA*

ELPH

Toshimi SUDA

ELPH

Hiroaki OHNISHI

ELPHFujio HINODE

ELPH

Shigeru KASHIWAGI

ELPHNorihito MURAMATSU

ELPH

Hidetoshi KIKUNAGA

ELPH

Hirokazu TAMURA

Graduate School of Science

Satoshi NAKAMURA

Graduate School of Science

Kouichi HAGINO

Graduate School of Science

Fuminori MISAIZU

Graduate School of Science

Yasushi KINO

Graduate School of Science

Nobuyuki UOZUMIGraduate School of Engineering

Atsuki TERAKAWA

Graduate School of Engineering

Masaki FUJITA

Institute for Materials Research

Yuji TAKAKUWA

Institute of Multidisciplinary Research for Advanced Materials

Takeo EJIMA

Institute of Multidisciplinary Research for Advanced Materials

Nobuyuki NISHIMORI

Institute of Multidisciplinary Research for Advanced Materials

Keiichi EDAMATSU

Research Institute of Electrical Communication

Masatoshi ITOH

Cyclotron and Radioisotope Center

Kenji TSUDA

Frontier Research Institute for Interdisciplinary Sciences* Chairperson

156

General Advisory Committee
2017

Hiroyuki HAMA*

ELPH, Tohoku University

Toshimi SUDA

ELPH, Tohoku University

Hiroaki OHNISHI

ELPH, Tohoku University

Hidetoshi KIKUNAGA

ELPH, Tohoku University

Hirokazu TAMURA

Graduate School of Science, Tohoku University

Yasushi KINO

Graduate School of Science, Tohoku University

Masatoshi ITOHCYRIC, Tohoku University

Kenji TSUDA

Frontier Research Institute for Interdisciplinary Sciences, Tohoku
University

Tomohiro UESAKARIKEN Nishina Center

Daisuke JIDO

Graduate School of Science and Engineering, Tokyo Metropolitan
University

Takashi NAKANORCNP, Osaka University

Tomohumi NAGAE

Graduate School of Science, Kyoto University

Ryukou KATO

Accelerator Laboratory, KEK

Hideaki OHGAKI

IAE, Kyoto University

Akihiko YOKOYAMA

College of Science and Engineering, Kanazawa University

Yasuji OURA

Graduate School of Science and Engineering, Tokyo Metropolitan
University* Chairperson

157

Program Advisory Committee
2017

Toshimi SUDA

ELPH, Tohoku University

Hiroaki OHNISHI

ELPH, Tohoku University

Shigeru KASHIWAGI

ELPH, Tohoku University

Hidetoshi KIKUNAGA

ELPH, Tohoku University

Satoshi NAKAMURA*

Graduate School of Science, Tohoku University

Asao YAMAMURA

Institute for Materials Research, Tohoku University

Kiyoshi TANIDA

ASRC, Japan Atomic Energy Agency

Megumi NARUKI

Graduate School of Science, Kyoto University

Masaru YOSOIRCNP, Osaka University

Yoshihiko SHOJILASTI, University of Hyogo

Yasuji OURA

Graduate School of Science and Engineering, Tokyo Metropolitan
University

Koichi TAKAMIYA

Research Reactor Institute, Kyoto University* Chairperson

158

VI. Approved Experiments

159

平成 㻞㻥 度前期採択課題一覧㻌

課題番号
2868
2869
2870
2871
2872
2873
2874
2875
2876

課

題

名

高エネルギー重イオン実験用 Si-W 電磁カロリメータ検出器(ALICE FoCal)および高時間分解能 MRPC-TOF の性能評価
放射性バナジウム V-48 を用いたバナジウム・レドックスフロ
ー電池の隔膜の研究
チャームバリオン分光実験(J-PARC E50)用シンチレーション
ファイバー検出器およびタイミング検出器のテスト実験
MPPC を用いた BGO 結晶カロリメーターの開発
Position Sensitive Scintillation Counter (PSSC)を用いたビーム形状診断装置の開発
BM4 ビームラインにおける実光子標識化装置の改善
d→K+n 反応での終状態相互作用を用いた Λn 相互作用測定
実験で用いる MRPC の性能評価
光子ビームを用いたハイパー核生成実験のための新 TOF 検出器の性能評価J-PARC KOTO 実験における undoped CsI 結晶両読みの性能評
価

申込責任者
中條 達也

白崎 謙次

白鳥 昂太郎
村松 憲仁
時安 敦史
金田 雅司
金田 雅司

永尾 翔

南條 創

160

平成 㻞㻥 度後期採択課題一覧㻌

課題番号
2877
2878
2879

課

題

名

ガンマ線と中性子の分別能力を高めた GAGG 電磁カロリメー
タの性能評価ハイパー核寿命測定に向けた大立体角検出器の性能評価
MPPC を用いたビーム位置検出器の開発と電子・陽電子ビー
ム形状の測定

申込責任者
外川 学
永尾 翔
宮部 学

2880

Multi-gap Resistive Plate Chamber のプレアンプ評価

金田 雅司

2881

d→d 反応を用いた'd 束縛状態の探索

藤岡 宏之

2882

FOREST 超前方荷電粒子検出で拓く物理

石川 貴嗣

2883

新光子標識化装置 TaggerⅡs の性能評価

田島 靖久

2884

エアロジェル・チェレンコフ検出器の基礎研究

村松 憲仁

2885
2886

家庭ごみ焼却スラグに含まれる希少金属元素の回収を目指した光量子放射化法による成分同定およびトレーサー作成
光量子放射化法によるプロメチウム（Pm）内包金属フラーレンの合成を目的とした RI 製造Ⅲ

秋山 和彦

秋山 和彦

2887

放射化イメージング分析用装置開発のための RI 製造

福地 知則

2888

光核反応収率の標準化とその利用に関する基礎研究

菊永 英寿

2889
2890
2891
（随時）

吸収体からの光を利用し高い精度を実現するサンプリング型
カロリメータの性能検証
Multi-gap Resistive Plate Chamber の時間分解能性能評価（国際共同大学院「宇宙創成物理学」高度実験）
短寿命 RI 供給プラットフォーム主催の RI 利用者研修会に用いる Co トレーサーの製造

竹下 徹

金田 雅司

池田 隼人

ELPH ANNUAL REPORT 2017
December 2018
Research Center for Electron Photon Science, Tohoku University
1-2-1, Mikamine, Taihaku, Sendai 982-0826, Japan

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