Research Group for Hadron Nuclear Physics

Group Leader : TAMURA Hirokazu
Members : SAKO Hiroyuki, HASEGAWA Shoichi, TANIDA Kiyoshi, SATO Susumu,ICHIKAWA Yudai, MARUYAMA Toshiki, NARUKI Megumi, MIAKE Yasuo, HASHIMOTO
Tadashi, YAMAMOTO Takeshi, Philipp GUBLER, YOSHIDA Junya, HAYAKAWA Shuhei,
SUZUKI Kei, NANAMURA Takuya, HINO Youta, ASHIKAGA Sakiko, SUZUKI Kazuki, IMAIKenIchi, NAGAMIYA Shoji, ESUMI ShinIchi, OYAMA Ken

The research objectives of the Hadron Nuclear Physics Groupare 1) experimental studies of exotic hadrons and nuclei withstrange and charm quarks, hot and dense partonic/hadronic matter
at J-PARC, BNL-RHIC, and Belle (II), and 2) theoretical studies
of exotic hadrons, nuclear matter, and neutron stars at low andhigh densities, including strangeness and charm quarks. Throughthese topics, we investigate many-body problems of quarks andhadrons in relation to Quantum Chromo Dynamics (QCD).
Hadron experimental studies at J-PARC
We found 35 double hypernuclei from 85 % of emulsion in JPARC E07 (studies of double Lambda hypernuclei) [1]. In−particular, the multiple hypernuclei events (Ξ + 14N→Ξ 15C)
that we identified will provide important information on theinteraction between Ξ and nucleons as shown in Fig. 1.
The proposal of J-PARC E72 (search for a new Λ resonance)
was officially approved by the Program Advisory Committee(PAC) of J-PARC in Dec. 2019 [2]. In preparation for theHyperon Spectrometer for E42 (H-dibaryon search), E45 (baryon
spectroscopy with πΝ→ππΝ reactions), and E72, a beam test of
the water Cherenkov counter was performed at ELPH, Tohoku
Univ. in Oct. 2019. As a result, the performance of the detector
was confirmed to be consistent with the simulation. Then, thewater Cherenkov counter prototype and the TPC of E42 weremoved to the K1.8 experimental area in Nov. 2019 to test themduring the E40 experiment in Feb. 2020. We also submitted aLetter-Of-Intent for a double K-nucleus K-K-pp to J-PARC PAC.

(Gaseous Electron Multiplier) Trackers on the E16 spectrometerfor electron measurements [3]. In addition, we developed andinstalled prototype detectors for charged hadron identification
with the time-of-flight measurement: a high-timing resolution
chamber (Multi-gap Resistive Plate Chamber), and start timing
counters. For J-PARC E03 (Ξ atom X-ray spectroscopy) which
will be performed late JFY2020, the maintenance work of Ge
detectors was completed in June 2019 and the tuning of
secondary kaon beamline was scheduled in Feb. 2020.
The beam time in Hadron Experimental Hall was postponed,
and the test of the E42 water Cherenkov counter and TPC, theE16 experiment, and the E03 beamline tuning were rescheduledin June 2020.
Other research activities
We proposed the future heavy-ion beam program at J-PARC
called J-PARC-HI to create dense baryonic matter to search forthe first order phase boundary and the QCD critical point in theQCD phase diagram [4]. J-PARC-HI was selected as one of thelarge research projects in Master Plan 2020 of Science Council ofJapan. We studied the beam transport of heavy-ion in the highmomentum beamline. and found that heavy-ion beam of 10
AGeV/c up to 108/spill can be transported in the current beamline
and radiation shields.
We are participating in Belle and Belle II experiments forstudies of hadrons with heavy quarks. Belle II is steadily taking
data and is expected to exceed the highest luminosity of Belle inearly JFY2020.
Reimei research programs
The Reimei research program “The Quark and Gluon Structureof Subatomic Particles” was proposed to advance research
discoveries in unfolding the quark and gluon structure of hadrons,
and develop plans for J-PARC-HI through an international
collaboration with Ken Hicks (Ohio Univ.). We held theworkshop “Synergies in Hadron Physics between J-PARC andJLab” in Nov. 2019 at Jefferson Lab., USA. Discussions in theworkshop included advanced plans for a new proposal to J-PARC
using the Drell-Yan method and the research preparations for theJ-PARC experiments E42, E45 and E72.

Fig.1: A hypernuclear event of Ξ- + 14N → Ξ15C.

J-PARC E16 aims at studying in-medium modification ofφ spectrum which decays into e+e- inside the nucleus. The firstbeam time of E16 was scheduled in Feb. 2020, with the proton
beam transported in the high-momentum beamline. We installed
the lead glass calorimeter, Hadron Blind Detectors, and GEM

References[1] J. Yoshida, et al, JPS Conf. Proc. 26 (2019) 023005.
[2] K. Tanida, AIP conf. Proc. 2130 (2019) 040019.
[3] S. Ashikaga, et al, JPS Conf. Proc. 26 (2019) 024005.
[4] H. Sako, Nucl. Phys. A982 (2019) 959-962.