First observation of ϕ-meson mass modification in nuclear medium

R. Muto, J. Chiba, H. En'yo, Y. Fukao, H. Funahashi, H. Hamagaki, M. Ieiri, M. Ishino, H. Kanda, M. Kitaguchi, S. Mihara, K. Miwa, T. Miyashita, T. Murakami, T. Nakura, M. Naruki, M. Nomachi, K. Ozawa, F. Sakuma, O. SasakiH. D. Sato, M. Sekimoto, T. Tabaru, K. H. Tanaka, M. Togawa, S. Yamada, S. Yokkaichi, Y. Yoshimura

研究成果: Article査読

5 被引用数 (Scopus)


We have measured e+ e- invariant mass spectra in 12 GeV p + A interactions at the KEK Proton-Synchrotron. The aim of the experiment is to detect possible in-medium modification of vector mesons at normal nuclear density. We used carbon and copper targets to study the nuclear size dependence of the e+ e- invariant mass spectra. A significant enhancement on the low-mass side of the φ{symbol} meson peak was observed in the low βγ region (β γφ{symbol} < 1.25) in the copper data. On the other hand, in the higher βγ region (β γφ{symbol} > 1.25), both the spectral shapes obtained from carbon and copper targets were consistent with the expected one from the simulation. This observation is consistent with a picture of the φ{symbol} modification in a nucleus, i.e. normal nuclear density, because such an effect should be visible only for slowly moving mesons produced in a larger nucleus.

ジャーナルNuclear Physics A
出版ステータスPublished - 2006 8月 7

ASJC Scopus subject areas

  • 核物理学および高エネルギー物理学


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