DEMONSTRATION OF REDUCTION METHODFOR TL-208 BACKGROUNDS USINGTOPOLOGICAL INFORMATION OFCHERENKOV LIGHT FOR ZICOS EXPERIMENT
Exploration of Particle Physics and Cosmology with Neutrinos
Workshop2020

22nd December, 2020
Grant-in-Aid for Scientific Research on Innovative Areas 19H05093
Miyagi University of Education

Y. Fukuda, Narengerile, A. Obata,Y. Kamei, D. Anzai

Kamioka Observatory, ICRR, Univ. of Tokyo S. Moriyama, K. Hiraide
Fukui University I. Ogawa
Tokyo University of Science

T. Gunji, S. Tsukada, R. Hayami

Institute for Materials Research, Tohoku University S. Kurosawa

Neutrinoless double beta decay[T1/20ν(0+ ->0+)]-1 =G0ν(E0,Z)|M0ν|2<mν>2 /me2
T1/2~a(Mt/∆E・B)1/2

a: abundance

M: target masst: measuring time ∆E: energy resolution B: BG rate

Requirement : Low BG, Large target mass, High E-resolution
Exploration of Particle Physics and Cosmology with Neutrinos workshop 2020

Dec 22nd, 20202

Conceptual design of ZICOS detector
Phys.Rev.Lett. 117 (2016) 082503

0𝜈𝜈
NEMO3 : 𝑇𝑇1/2> 9.1 × 1021 yrs

96Zr : 45kg (nat.) → 865kg(50% enrich)→1/20 BG0𝜈𝜈𝑇𝑇1/2> 4 × 1025 yrs → 2 × 1026 yrs → ~1 ×1027yrs

Exploration of Particle Physics and Cosmology with Neutrinos

Dec 22nd, 20203

Liquid Scintillator solving Zr(iPrac)4Zr(CH3COCHCOOCH(CH3)2)4= Zr(iPrac)4
mw : 663.87Zr(iprac)4 2242mg, PPO
999mg and POPOP 10mg
solved in 20mL Anisole> 70g/L of Zirconium could be solved in anisole.
Exploration of Particle Physics and Cosmology with Neutrinos workshop 2020

Dec 22nd, 2020

4

Measurement for energy resolution by 20%
photo coverage

σ/E=7.0%@982
keV&20%photocoverage
2.2%@3.35MeV&60% photo
coverage
Exploration of Particle Physics and Cosmology with Neutrinos workshop 2020

Dec 22nd, 2020

5Discrimination of signal and BG
0νββ event
e-Reconstructed vertex byescintillation light

β decay
2.6MeV γ
Reconstructed vertex
by Cherenkov light
Balloon or
surface ofdetector
Exploration of Particle Physics and Cosmology with Neutrinos workshop 2020

e-Dec 22nd, 20206

Topological info. : averaged angle
Average directione- = Σ didi θi

Averagedangle= Σ θi
Nhit

Average angle with respect to averaged direction
for single electron seems to have a peak at 48
degree which is almost same as Cherenkov angle.
Exploration of Particle Physics and Cosmology with Neutrinos workshop 2020

Dec 22nd, 2020

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BG reduction using topological information
Simulated by EGS5

Simulated by EGS5

78%
remainVertex position
Double beta decay event sample
Simulated by EGS5

93%
cut

Topological information from
PMT position which received
PMT hit pattern of 208Tl BG and Cherenkov lights could be
used for reduction of 208Tl BG.
0νββ signal
Vertex position

Exploration of Particle Physics and Cosmology with Neutrinos workshop 2020

Dec 22nd, 20208

Measurement of pulse shape difference
FADC digitizer: CAEN V1751
 10 bit 2 GS/s (interleaved) – 1 GS/s ADC
 4-8 channel
 FPGA for real time Digital Pulse Processing: Pulse Shape Discrimination (DPP-PSD)
 Zero Length Encoding (DPP-ZLEplus)
 0.2 or 1 Vpp input dynamics single ended or 1 Vpp differential
 16-bit programmable DC offset adjustment: ±0.5 V / ±0.1 V
 Trigger Time stamps
 Memory buffer: up to 14.4 MS/ch (28.8 MS/ch @2 GS/s)
 Programmable event size and pre-post trigger adjustment
 Analog Sum/Majority and digital over/under threshold flags for
Global Trigger logic
 Front panel clock In/Out available for multiboard synchronisation(direct feed through or PLL based synthesis)
 16 programmable LVDS I/Os
 Optical Link interface (CAEN proprietary protocol)
 VME64X compliant interface A2818(PCI) / A3818 (PCIe) Controller available for handling up to
8/32 modules Daisy chained via Optical Lin Firmware upgradeable via VME/Optical Link
 Libraries, Demos (C and LabView) and Software tools for Windows andLinuxDec 22nd, 2020
Exploration of Particle Physics and Cosmology with Neutrinos workshop 20209

Measurement of pulse shape difference
Photomultiplier : Hamamatsu H2431-50 (R2083)

 Spectral response ：４００K QE: 25% at peak Dynode structure : linear focused/8 dinodes
 High voltage ：３０００V
 Gain：2.5×106 dark current :100nA (H6410:10nA)
 Time response ：0.37ns(TTS) 0.7ns（rise time）
Exploration of Particle Physics and Cosmology with Neutrinos workshop 2020

Dec 22nd, 202010

Pulse shape of Cherenkov and scintillation• Pulse shape of 90Sr usingH2431-50 measured by
V1751 with DES mode(2GS/s)• Decay time of scintillation :4.57ns and 8.38ns• Rise time of scintillation :1.45ns• Rise time of Cherenkov :0.75nsUse the charge ratio Qtime/Qtotal. Here, Qtimeis FADC
value in each time, and Qtotalis sum of FADC value
between 55ns and 80ns.
Exploration of Particle Physics and Cosmology with Neutrinos workshop 2020

Dec 22nd, 202011

Qtotal distribution for γ sources••••

60Co (1.17MeV/1.33MeV)

Compton edge： 1.04MeV
137Cs (662keV)
Compton edge： 478keV
133Ba (356keV)
Compton edge： 207keV
57Co (122keV)
Under Cherenkov threshold(169kev)

Pulse shape with charge
ratio in each FADC time.
Exploration of Particle Physics and Cosmology with Neutrinos workshop 2020

Dec 22nd, 2020

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Charge ratio in rise time using ZICOS LS•

There is difference ofshape between t=57ns
and 58ns
Charge ratio looks
depend on the energy
For t>58.5ns, all shapes
were almost same.

••Cherenkov looks dominant
between 57ns and 58ns.

Template waveform ofscintillation between 57.0ns
and 58.0ns for 57Co.
Exploration of Particle Physics and Cosmology with Neutrinos workshop 2020

Dec 22nd, 202013χ2distribution using 57Co template• Most of backgrounds
have lower χ2 than 1.0• Most of backgrounds
have lower energy than
Cherenkov threshold,then only scintillation
was seen.

It seems to events with
Cherenkov lights shouldhave large χ2 value.
Exploration of Particle Physics and Cosmology with Neutrinos workshop 2020

Dec 22nd, 202014

Measured by fixed energy fixed direction events

χ2>0.1：22events/28events=78.6%

BG events=3evets

Fixed energy : 835keV
ADC ch~3400cn
If the events with χ2>0.1
should have Cherenkov
lights, is this inefficiency
21.4±9.6% correct?

Exploration of Particle Physics and Cosmology with Neutrinos workshop 2020

Dec 22nd, 202015

Measured by Compton edge event and BG sample

χ2 ＜0.1(scintillation like)
403/3970 = 10.4±0.5% forCompton edge event

1772/3606=49.1±1.4% for
BG sample
Inefficiency value between
Compton edge and BG
sample differs with 2.86σ.
Topology of Cherenkov
lights for O(1)MeV ewas confirmed.

Exploration of Particle Physics and Cosmology with Neutrinos workshop 2020

Dec 22nd, 202016

Measurement of topological information(averaged angle) using HUNI-ZICOS

Exploration of Particle Physics and Cosmology with Neutrinos workshop 2020

Dec 22nd, 202017

3/8” photomultiplier H3164-12(R1635)

 Sensitivity：４００K
 Dynode type : Line focus/8dynode Applied voltage：125０V
 Gain：1.0×106 Dark current:50nA
 Time characteristics：0.5ns(TTS) 0.8ns（rise time）
Exploration of Particle Physics and Cosmology with Neutrinos workshop 2020

Dec 22nd, 202018

Pulse shape measurement by H3164-12

Cherenkov dominant

Scintillation dominant
Exploration of Particle Physics and Cosmology with Neutrinos workshop 2020

Dec 22nd, 202019

Pulse Shape Discrimination using H3164-12

Possible but need tuning. 20

Exploration of Particle Physics and Cosmology with Neutrinos workshop 2020

Dec 22nd, 2020

Hemisphere flask and PMT fixing jig for HUNIZICOS

Exploration of Particle Physics and Cosmology with Neutrinos workshop 2020

Dec 22nd, 202021

Flash ADC V1742 and PMT HV system

HV system worked well, butFADC was not checked yet,because the delivery wasdelayed due to COVID19.
Exploration of Particle Physics and Cosmology with Neutrinos workshop 2020

Dec 22nd, 202022Summary••

High Zr concentrated liquid scintillator is available.
Expected energy resolution 2.2％＠3.35ＭｅV+60% photocoverage→ need to confirm with real 60% Photo coverage• To establish background reduction technique for 208Tl decay→ topological information using Cherenkov lights is useful.
① Pulse shape discrimination for selection of PMT which
receives Cherenkov lights : almost done
② Confirmation of topological information : HUNI-ZICOS
will be ready to measure soon
③ Demonstration of βγ events reduction using topologicalinformation : UNI-ZICOS will do next year

Exploration of Particle Physics and Cosmology with Neutrinos workshop 2020

Dec 22nd, 202023

Demonstration of BG reduction of 208Tl• Direct reduction for βγ events by UNI-ZICOS

Exploration of Particle Physics and Cosmology with Neutrinos workshop 2020

Dec 22nd, 202024

Summary••

High Zr concentrated liquid scintillator is available.
Expected energy resolution 2.2％＠3.35ＭｅV&20% photocoverage→ need to confirm with real 60% Photo coverage• To establish background reduction technique for 208Th decay→ topological information using Cherenkov lights useful.
① Pulse shape discrimination for selection of PMT which
receives Cherenkov lights : almost done
② Confirmation of topological information : HUNI-ZICOS will
be ready to measure soon
③ Demonstration of βγ events reduction using topologicalinformation : UNI-ZICOS will do next year
• Physics program (96Zr 2νββ T1/2 measurement) with ZICOS-I
will start and get results within 5 years. Stay tuned!

Exploration of Particle Physics and Cosmology with Neutrinos workshop 2020

Dec 22nd, 202025

Measurement of T1/2 for 96Zr 2νββ using ZICOS-I• First physics program for confirmation of NEMO-3
・20cm diameter flask
using Ultra-pure quartz
and 30 low ＢＧ PMT
R3378-50・300g of Zr(iPrac)4
corresponds to 1g 96Zr
・According to NEMO-3results, could expect
200 2νββ events with 1year measurement
・location : Kamioka
mine
Exploration of Particle Physics and Cosmology with Neutrinos workshop 2020

Dec 22nd, 202026

Summary••

High Zr concentrated liquid scintillator is available.
Expected energy resolution 2.2％＠3.35ＭｅV&20% photo
coverage→ need to confirm with real 60% Photo coverage• To establish background reduction technique for 208Th decay→ topological information using Cherenkov lights useful.
① Pulse shape discrimination for selection of PMT which
receives Cherenkov lights : almost done
② Confirmation of topological information : HUNI-ZICOS will
be ready to measure soon
③ Demonstration of βγ events reduction using topologicalinformation : UNI-ZICOS will do next year
• Physics program (96Zr 2νββ T1/2 measurement) with ZICOS-I
will start and get results within 5 years. Stay tuned!
• 115In loaded LS for pp solar-ν will be evaluated by new tech.
using topological information from multi Compton.
Exploration of Particle Physics and Cosmology with Neutrinos workshop 2020

Dec 22nd, 202027

Evaluation of 115In loaded in liquid
scintillator for solar pp neutrino

本研究でO(1MeV)程度の電子から放射されるチェレンコフ光も位相幾何学情報を有していることが示唆されたことから、115Inのニュートリノ捕獲で遷移した115Sn*から放出する497keVのガンマ線が光電吸収や多重コンプトン散乱しても、その距離が20cm以内であり、散乱電子からチェレンコフ光を放射すれば、離れた場所で115Inの自然ベータ崩壊が同時に発生し、各々の電子がチェレンコフ光を放出する
場合とチェレンコフ光の位相幾何学的情報が異なるはずであり、In(iPrac)3含有の大型単相LS検出器でも、チェレンコフ光による平均角を用いれば、検出器を細分化することなくsolar ppνが観測できる可能性があることを着想した。
Exploration of Particle Physics and Cosmology with Neutrinos workshop 2020

Dec 22nd, 202028

Backup slides

Exploration of Particle Physics and Cosmology with Neutrinos workshop 2020

Dec 22nd, 2020

29

9ZICOSexperiment for neutrinoless double
beta decay using 96Zr
Liquid Scintillator：(1) 10 wt.% Zr(iprac)4 loaded in
Liquid Scintillator(2) 3~4% at 3.35MeV of energy
resolution with 64% photo
coverage and long attenuation
length.

3.5m

Pure water surrounding innerdetector in order to veto muons andexternal backgrounds.
Inner detector with ~64% photo
coverage 20” PMT including 1.7ton
Zirconium loaded 113 tons LS infiducial volume. (Total vol. : 180tons)
Exploration of Particle Physics and Cosmology with Neutrinos
workshop 2020

10m10mPurpose:① Direct measurement of 0νββ
② Confirm parameter of nuclear
matrix element modelDec 22nd, 202030

Performance of liquid scintillator
Measured at several conditions of PPO concentration

48.7±7.1% light yield tostandard cocktail was
obtained at 10wt.%
concentration.

13.0±2.0%√(64%/9.2%)X(3.35MeV/1.03MeV)= 2.7±0.4% at 3.35MeV

Exploration of Particle Physics and Cosmology with Neutrinos workshop 2020

Dec 22nd, 202031

Decay scheme of 208Tｌ

The vertex position reconstructedby scintillation might be within
fiducial volume due to gammas.
Exploration of Particle Physics and Cosmology with Neutrinos workshop 2020

Dec 22nd, 202032