Research Group for Hadron Nuclear Physics
Group Leader : Makoto OkaMembers : Hiroyuki Sako, Toshiki Maruyama, Shoichi Hasegawa, Kiyoshi Tanida, Susumu Sato,Megumi Naruki, Philipp Gubler, Tadashi Hashimoto, Yudai Ichikawa, Takayasu Sekihara, Junya
Yoshida, Hiroyuki Ekawa, Shuhei Hayakawa, Sakiko Ashikaga, KenIchi Imai, Shoji Nagamiya,Atsushi Hosaka, Emiko Hiyama

The research objectives of the Hadron Nuclear Physics Groupare 1) experimental studies of exotic hadrons and nuclei withstrange and charm quarks, and hot and dense quark/hadronicmatter at J-PARC and BNL-RHIC, and 2) theoretical studies of
exotic hadrons, nuclear matter, and neutron stars at low and highdensities, including strangeness and charm quarks. Throughthese topics, we study many-body problems of quarks andhadrons in relation with Quantum Chromo Dynamics (QCD).
Hadron experimental studies at J-PARC
We performed the J-PARC E07 experiment to investigate
double hypernuclei in the K-pK+- reaction using the hybridemulsion method, where we associate tracks from Silicon Strip
Detectors with trajectories in emulsions. We irradiated 118
emulsion modules with a K- beam, which are expected toinclude 104 stopped - [1,2]. We have already found somecandidate events with a hypernucleus, as shown in Fig. 1.
The Stage-2 request to the Program Advisory Committee(PAC) of J-PARC for the H-dibaryon search experiment (JPARC E42) was officially approved in July 2017. In preparation
for the Hyperon spectrometer for the baryon spectroscopy
experiment with NN reactions (E45), in collaboration
with Research Fellow, Ken Hicks of Ohio University, weachieved 180 ps time resolution of a prototype TPC Hodoscope,
which is used for two-charged particle trigger. We also designed
a liquid hydrogen target system and made the TPC target holder
to accommodate the target. We wrote the technical design
review and undertook a review for our Stage-2 request to PAC
in Jan. 2018. The technical part of E45 has been mostly
approved, while we are asked for more detailed beam time
estimation with further physics consideration.
 track

10msingle  hypernuclei
Fig.1 An event of twin single  hypernuclei in emulsion at J-PARC E07.

Tanida and Hicks proposed a new experiment to search for anew (1670) resonance in the K-p reaction. A hint for thisresonance was previously observed at Belle and Crystal Ballexperiments. Since this resonance does not exist in quark
models, it could be an exotic hadron. The experiment (P72) wasreviewed in Jan. 2018, and approved for Stage-1 (for physicsimportance).

Theoretical studies on exotic hadrons
We performed various theoretical studies for exotic hadrons andnuclei with strangeness and charm, such as theoretical studies
for kaonic nuclei based on the J-PARC E15 experiment [3],properties of vector mesons in hot matter [4], and exotic hadrons
with charm [4,5]. As activities of the Theoretical Physics
Institute, we held 12 seminars, and a mini-workshop on
theoretical physics with various kinds of physics topics based on
the keyword of strong magnetic field. We are preparing to forma new theoretical research group in ASRC involving diverse
fields such as hadron and nuclear physics, and condensed matterphysics.
Other research activities
At RHIC, in p+Au collisions with polarized proton beams, wemeasured the left-right asymmetry of forward neutrons [6]. We
obtained striking results that the asymmetry has the opposite
sign to p+p data. The source of the difference has not been
understood.
We are developing the design for the future heavy-ion
program at J-PARC (J-PARC-HI). We are revising thespectrometer design based on a dipole magnet and Time
Projection Chamber for easier implementation. We have a newinternational collaboration with Vinca Institute of University ofBelgrade and University of Grenoble. We continue R&D for theproject on Time-of-Flight detector based on Multi-Resistive
Plate Chamber (MRPC), as well as a fast data acquisition
system with triggerless readout.
Reimei research “Collaborative studies on baryon
spectroscopy at J-PARC between theory and experiment”
In this Reimei research program, we studied baryon excitedstates and dense nuclear matter at J-PARC with Ken Hicks as PI.
We prepared for the E45 experiment, and we proposed the P72experiment. We held the Mini Workshop “Light baryon andhyperon spectroscopy at J-PARC” in June 2017, the and Reimei
Workshop on Hadronic Resonances and Dense Nuclear Matteron Dec. 2017. The latter had 74 participants including 28
foreign participants, where we discussed hadron physics andheavy-ion physics related to J-PARC. We also held a J-PARCHI collaboration meeting to discuss the project strategy.
References[1] H. Ekawa, JPS Conf. Proc. 17, 033002 (2017).
[2] S. Hayakawa, JPS Conf. Proc. 17, 033003 (2017).
[3] T. Sekihara, E. Oset and A. Ramos, Acta Phys. Polon. B48,1869 (2017).
[4] P. Gubler and D. Satow, Phys. Rev. D96, 114028 (2017).
[5] K. Ohtani, K-J. Araki, M. Oka, Phys. Rev. D96, 055208(2017).
[6] C. Aidala, K. Tanida, et al, Phys. Rev. Lett. 120, 022001(2017).