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arXiv · 2507.00420

Analysis of spectral modification of $ϕ$ mesons at finite density using a transport approach in the 12 GeV pA reactions

PS E325 Collaboration·Masaya Ichikawa·Philipp Gubler·Junsei Chiba·Hideto En'yo·Yoshinori Fukao·Haruhiko Funahashi·Hideki Hamagaki·Masaharu Ieiri·Masaya Ishino·Hiroki Kanda·Masaaki Kitaguchi·Satoshi Mihara·Koji Miwa·Takuya Miyashita·Tetsuya Murakami·Ryotaro Muto·Terunao Nakura·Megumi Naruki·Kyoichiro Ozawa·Fuminori Sakuma·Osamu Sasaki·Michiko Sekimoto·Tsuguchika Tabaru·Kazuhiro Tanaka·Manabu Togawa·Satoru Yamada·Satoshi Yokkaichi·Yoshio Yoshimura
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Abstract

The hadron spectrum at finite density is an important observable for exploring the origin of hadron masses. In the KEK-PS E325 experiment, the di-electron decays of phi mesons inside and outside nuclei were measured using 12 GeV pA reactions. In the previous analysis, a significant excess was observed on the low-mass side of the phi meson peak in the data for slow-moving phi mesons ($βγ=p_ϕ/m_ϕ<1.25$) with the Cu target, and in-medium vector meson spectral modification was verified. We newly employed the PHSD transport approach to take into account the time evolution of spatial density distribution of the target nuclei. Consistent with the previous analysis, a significant excess was observed in the present analysis as well. It was found that incorporating momentum dependence into the spectral modification leads to better agreement with the experimental results. For the slow-moving $ϕ$ mesons with the Cu target, the newly obtained modification parameters are consistent with those from the previous analysis within the uncertainties.

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PS E325 Collaboration, Masaya Ichikawa, Philipp Gubler, Junsei Chiba, Hideto En'yo, Yoshinori Fukao, Haruhiko Funahashi, Hideki Hamagaki, Masaharu Ieiri, Masaya Ishino, Hiroki Kanda, Masaaki Kitaguchi, Satoshi Mihara, Koji Miwa, Takuya Miyashita, Tetsuya Murakami, Ryotaro Muto, Terunao Nakura, Megumi Naruki, Kyoichiro Ozawa, Fuminori Sakuma, Osamu Sasaki, Michiko Sekimoto, Tsuguchika Tabaru, Kazuhiro Tanaka, Manabu Togawa, Satoru Yamada, Satoshi Yokkaichi, Yoshio Yoshimura. 2025-07-01. Analysis of spectral modification of $ϕ$ mesons at finite density using a transport approach in the 12 GeV pA reactions. https://doi.org/10.1093/ptep%2Fptaf108

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