ACTA

Towards the Measurement of the Mass Modifications of Vector Mesons in a Finite Density Matter

K. Ozawa^{a, b, c}, K. Aoki^a, D. Arimizu^d, S. Ashikaga^e, W.C. Chang^f, T. Chujo^b, K. Ebata^d, H. En'yo^g, S. Esumi^b, H. Hamagaki^h, R. Honda^a, M. Ichikawa^{d, i, j}, S. Kajikawa^k, K. Kanno^g, Y. Kimura^l, A. Kiyomichi^m, T.K. Kondoⁿ, S. Kyan^b, C.H. Lin^f, C.S. Lin^f, Y. Morino^a, H. Murakami^o, T.N. Murakami^{c, i}, R. Muto^a, W. Nakai^a, S. Nakasuga^{d, j}, M. Naruki^{d, j}, T. Nonaka^b, H. Noumi^{a, e}, T. Sakaguchi^p, H. Sako^j, F. Sakuma^g, S. Sato^j, S. Sawada^a, M. Sekimoto^a, K. Shigakiⁿ, K. Shirotori^e, H. Sugimura^a, T.N. Takahashi^g, Y. Takaura^d, R. Tatsumi^l, K. Tsukui^b, P.H. Wang^f, K. Yahiro^d, K.H. Yamaguchi^d, S. Yokkaichi^g
^aInstitute of Partile and Nuclear Studies, KEK, 1-1 Oho, Tsukuba, Ibaraki 305-0801, Japan
^bCenter for Integrated Research in Fundamental Science and Engineering, University of Tsukuba, Tsukuba, Ibaraki 305-8577, Japan
^cDepartment of physics, University of Tokyo, 7-3-1 Hongo, Tokyo 113-0033, Japan
^dDepartment of Physics, Kyoto University, Kitashirakawa Sakyo-ku, Kyoto 606-8502, Japan
^eResearch Center for Nuclear Physics (RCNP), Osaka University, 10-1 Mihogaoka, Ibaraki, Osaka 567-0047, Japan
^fInstitute of Physics, Academia Sinica, Taipei 11529, Taiwan
^gRIKEN Nishina Center for Accelerator-Based Science, RIKEN, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan
^hInstitute for Innovative Science and Technology, Nagasaki Institute of Applied Science, 3-1 Shuku-machi, Nagasaki 851-0121, Japan
ⁱRIKEN Cluster for Pioneering Research, RIKEN, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan
^jAdvanced Science Research Center, Japan Atomic Energy Agency, 2-4 Shirakata, Tokai, Ibaraki 319-1195, Japan
^kDepartment of Physics, Tohoku University, Sendai 980-8578, Japan
^lInstitute of Physics, Osaka University, Toyonaka, Osaka 560-0043, Japan
^mJapan Synchrotron Radiation Research Institute (JASRI), 1-1-1 Koto, Sayo, Hyogo 679-5198, Japan
ⁿGraduate School of Science, Hiroshima University, 1-3-1 Kagamiyama, Higashi-Hiroshima 739-8526, Japan
^oCenter for Nuclear Study, Graduate School of Science, University of Tokyo, 7-3-1 Hongo, Bunkyo, Tokyo 113-0033, Japan
^pBrookhaven National Laboratory, Upton, NY 11973-5000, USA

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An experiment is being carried out at J-PARC - Japan Proton Accelerator Research Complex - to study the origin of hadron mass and the partial restoration of chiral symmetry of quantum chromodynamics in a finite density matter. The experiment, which is called the J-PARC E16 experiment, aims to measure the mass spectra of vector mesons in nuclei due to finite density effects. Previous measurements were performed at KEK-PS proton synchrotron and showed mass modifications of vector mesons in nuclei. A new experiment aims to confirm the results of KEK-PS with larger statistics to have a detailed study. Mass spectra of vector mesons are measured using electron-positron decays in proton-nucleus reactions. A new beam line is built to provide a high-intensity proton beam for the experiment, and decayed electrons and positrons are detected and identified by a newly constructed spectrometer. The experiment started the acquisition of pilot data to evaluate the performances of the beam line and the spectrometer in 2020 and 2021. The spectrometer worked well, and physics data taking will start in 2023.

DOI:10.12693/APhysPolA.142.399
topics: hadron mass, chiral symmetry, vector mesons, finite density matter