Research Group for Hadron Nuclear Physics
Group Leader : Makoto Oka
Members : Hiroyuki Sako, Toshiki Maruyama, Shoichi Hasegawa, Susumu Sato, Kiyoshi Tanida,Sanghoon Hwang, Kenji Hosomi, Hitoshi Sugimura, Yudai Ichikawa, Hiroyuki Ekawa, Shuhei
Hayakawa, Shinji Kinbara, Shoji Nagamiya, Atsushi Hosaka, Emiko Hiyama

The research objectives of our group are 1) experimental
studies of exotic hadrons and nuclei with strangeness and charm,and high-density matter at J-PARC and BNL-RHIC, 2)
theoretical study of nuclear matter at low and high densities andthe role of strangeness and charm in nuclear matter and neutronstars. Through these topics, we study many-body problems ofquarks and hadrons in relation with Quantum Chromo
Dynamics (QCD).
Hadron physics experiments at J-PARC
We measured the gamma ray emitted by the first excited statein 4He. The excitation energy of this state is found to differ
from that of the mirror nucleus, 4H, by 320 keV, indicating alarge charge-symmetry breaking effect [1]. Details are shown in
the research highlight of this Annual Report.
We conducted pilot runs of experiments E05 (search for hypernucleus with a spectrometer) and E07 (search for a doublehypernucleus in emulsion) in October and November, 2015.
For E05, we took preliminary data for the 12C(K-,K+) reaction tosearch for  hypernuclei. For E07, we tested the marking of thebeam position on an emulsion with pbar and K- beams.
We also took 12C(K-,p) reaction data in the E05 pilot run to___study the K -nucleus interaction. A previous study of the samereaction (KEK-E548) had an experimental bias by requiring achaged particle in a decay detector. Our experiment measured
unbiased events successfully and the analysis is underway.
We have completed the construction of the superconducting
Helmholtz magnet for E42 (H-dibaryon search in (K-,K+)
reaction) and E45 (baryon resonance spectroscopy in ,2)
reactions) experiments in March 2016. We tested the Time
Projection Chamber (TPC) for these experiments withradioactive sources and a UV laser. We developed a dataacquisition system and performed readout tests of the TPC using
GET (General Electronics for TPC). Our request for the secondstage approval of E42 was reviewd by the J-PARC PAC inJanuary 2016. We were given homework on the magnet and theTPC and progress is underway to solve all remaining issues.
High energy heavy-ion physics at RHIC and J-PARC
The RHIC-PHENIX experiment aims at studies of quarkgluon plasma. In 2015, we studied the reactions p+p, p+Au, andp+Al at nucleon-nucleon center-of-mass energy of 200 GeV.
The J-PARC Heavy-Ion project (J-PARC-HI) aims to explore
QCD phase structures at extremely high baryon density with theworld’s most intense heavy-ion beams. In the Master Plan of theScience Council of Japan, R&D for the project has been
included. Design of the heavy-ion acceleration scheme with a
new heavy-ion linac and a heavy-ion booster ring with existing
3-GeV RCS and 50-GeV MR has been established. Detailed
simulation studies for dilepton spectra were done with a large
acceptance toroidal spectrometer [2]. The white paper of JPARC-HI has been completed in May 2016.

Hadron Theory Research and Theoretical Physics InstituteThe J-PARC experimental programs are quite competitive andhighly regarded internationally, and they rely on strong
theoretical support. Our theorists benefit from working closelywith experimentalists and have established collaborative
research in multi-strange hadron/nuclear physics, charm hadron
physics, and properties of dense hadronic matter. Much effort
has been devoted to build a theory group to support J-PARCexperiments. We started the Theoretical Physics Institute (TPI)
as a (virtual) theory group at ASRC, aiming to host crossdisciplinary collaborations among the theorists in ASRC. The
TPI activities include the Kick-off Meeting in August, and aseries of TPI Lectures, for which we invited several guest
speakers covering hadron, nuclear and condensed-matterphysics.
The Reimei Program and International Collaborations
A Reimei Program on "Hadron Physics in Extreme Conditions
at J-PARC" was successfully carried out with Hyun-Chul Kim(Inha Univ., Korea) as the PI. We had a fruitful researchcollaboration, publishing papers on heavy quark hadrons [3].
We held the 31st Reimei workshop on Hadron Physics inExtreme Conditions at J-PARC at ASRC in January 2016, with72 participants (24 from abroad). The program consisted of akeynote talk by W. Weise (Munchen), and invited talks on thesubjects of heavy quark hadrons, hypernuclear physics, hadrons
in medium, exotic hadrons and heavy-ion physics.
We established international research exchange agreementswith the Inha University and the European Centre for
Theoretical Studies in Nuclear Physics and Related Areas (Italy),
from which we invited researchers to the Reimei workshop.

Fig. 1: Predicted missing mass spectrum of charmed baryons [3].

References[1] T.O. Yamamoto, H. Ekawa, H. Hasegawa, H. Hosomi, Y.
Ichikawa, H. Sako, S. Sato, H. Sugimura, K. Tanida, et al.
Phys. Rev. Lett. 115, 222501 (2015) 5.
[2] Future heavy-ion program at J-PARC, H. Sako, JPS Conf.
Proc. 8 (2015) 022010.
[3] Productions and decays of charmed baryons, A. Hosaka, E.
Hiyama, S.H. Kim, H.-C. Kim, H. Nagahiro, H. Noumi, M.
Oka, K. Shirotori, T. Yoshida, S. Yasui, Nucl. Phys. A 954(2016) 341.