Research Group for Hadron Nuclear Physics
Group Leader : Hirokazu Tamura
Members : Hiroyuki Sako, Toshiki Maruyama, Shoichi Hasegawa, Kiyoshi Tanida, Susumu Sato,Yudai Ichikawa, Megumi Naruki, Yasuo Miake, Philipp Gubler, Tadashi Hashimoto, Takeshi
Yamamoto, Takayasu Sekihara, Junya Yoshida, Hiroyuki Ekawa, Shuhei Hayakawa, Takayuki
Ezoe, Sachio Iwasaki, Takuya Nanamura, Kazuki Suzuki, Youta Hino, Sakiko Ashikaga, Kazuki
Kuwata, Hyun-Chul Kim, 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 partonic/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 investigate many-body problems of quarks andhadrons in relation to Quantum Chromo Dynamics (QCD).
Hadron experimental studies at J-PARC
We made progress in the data analysis for the J-PARC E07
experiment to search for double hypernuclei and found 22
double hypernuclei, among which we uniquely identified a ΛΛBe[1], as shown in Fig. 1 (Also see the research highlight of ourgroup).
The Stage-2 request to the Program Advisory Committee(PAC) of J-PARC for the baryon spectroscopy experiment withπNππN reactions (J-PARC E45) was officially approved inJuly 2018. In preparation for the Hyperon spectrometer for E42(H-dibaryon search), E45, and E72 (search for a new Λresonance), a high-rate beam tests up to 1 MHz at HIMAC wasperformed. As a result, a good efficiency, position resolution,and track reconstruction performance were achieved. We alsoachieved 140 ps timing resolution of a prototype TPC
Hodoscope and constructed a liquid hydrogen target system.
These achievements were followed by the successful
performance of a 24-hour test of the superconducting dipole
magnet in the summer period.

“MINO event”

10µm
Fig.1 An event of double Λ hypernuclei (MINO event) in emulsion at JPARC E07.

Theoretical studies on exotic hadrons
Throughout 2018, we performed various theoretical studies forexotic hadrons and nuclei with strangeness and charm, such as anucleon-Omega dibaryon [2], production of η’d bound state inγdηd [3], properties of vector mesons in hot matter, andcharmonium spectra at finite temperature [4]. As the Theoretical
Physics Institute, we held 10 seminars and one of the lectureseries (by Y. Utsuno) on theoretical and experimental hadron
nuclear physics. In Apr. 2019, we started a new theoreticalresearch group in ASRC involving diverse fields, such as hadron,nuclear, and condensed matter physics.
Other research activities
At Belle, we were able to observe an Omega excited state forthe first time [5] and two Press Releases were published on theobservation. One for the discovery of the nucleus with K- mesonand two protons in Jan. 2019, and the other is for the discoveryof MINO event [1] in Feb. 2019.
We proposed the future heavy-ion program at J-PARC called
J-PARC-HI to Japanese Nuclear Physics Community and theReimei Workshop “Physics of dense matter and strangeness atJ-PARC-HI” was held to discuss the proposal. In Nuclear
Physics Committee Meeting of Dec. 2018, large nuclear physics
projects including J-PARC-HI were discussed and thecommittee endorsed J-PARC-HI with a high priority. We
submitted the proposal for Master Plan of Science Council ofJapan in Mar. 2019.
Reimei research programs
In the Reimei research program “New Aspects of Hadron
Spectroscopy and Exploration of Dense Nuclear Matter at JPARC”, we studied baryon excited states and dense nuclear
matter at J-PARC with Prof. Ken Hicks (Ohio Univ.) as
principal investigator (PI). We held the workshop “Physics ofdense matter and strangeness at J-PARC-HI” in Dec. 2018 as
described above and “Experimental and Theoretical Hadron
Physics: Recent Exciting Developments on Hadronic
Resonances and Dense Nuclear Matter” in Jan. 2019. The latterhad 50 participants including 12 foreign participants, where we
discussed hadron physics and heavy-ion physics related to JPARC.
In another Reimei research program “Universal physics inMany-Body Quantum Systems – From Atoms to Quarks –”, wemade cross-disciplinary studies of many body quantum systems
with Prof. Hans-Werner Hammer (TU Darmstadt) as PI. Inaddition, we held the Reimei Workshop “Universal physics inMany-Body Quantum Systems - From Atoms to Quarks -” inDec. 2018 with 54 participants including 8 foreign participants.
References[1] H. Ekawa, Prog. Theor. Exp. Phys. 2019, 021D02 (2019).
[2] T. Sekihara, Y. Kamiya and T. Hyodo, Phys. Rev. C98,015205[3] T. Sekihara, H. Fujioka and T. Ishikawa, Phys. Rev. C97,045202.
[4] K-J. Araki, K. Suzuki, P. Gubler, M. Oka, Phys. Lett. B 780,
48 (2018).
[5] J. Yelton, K.Tanida, et al. (Belle Collaboration), Observationof an excited Ω- baryon, Phys. Rev. Lett. 121, 052003 (2018).