APS » PROLA » Phys. Rev. Lett. » Volume 86 » Issue 22

Phys. Rev. Lett. 86, 5019 - 5022 (2001)

Observation of ρ/ω Meson Modification in Nuclear Matter
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K. Ozawa *, H. En'yo, H. Funahashi, M. Kitaguchi, M. Ishino †, H. Kanda ‡, S. Mihara §, T. Miyashita **, T. Murakami, R. Muto, M. Naruki, F. Sakuma, H. D. Sato, T. Tabaru, S. Yamada, S. Yokkaichi ††, and Y. Yoshimura ‡‡
Department of Physics, Kyoto University, Kitashirakawa Sakyo-Ku, Kyoto 606-8502, Japan

J. Chiba, M. Ieiri, M. Nomachi , O. Sasaki, M. Sekimoto, and K. H. Tanaka
Institute of Particle and Nuclear Studies, KEK, 1-1 Oho, Tsukuba, Ibaraki 305-0801, Japan

H. Hamagaki
Center for Nuclear Study, Graduate School of Science, University of Tokyo, 7-3-1 Hongo, Tokyo 113-0033, Japan

Received 14 November 2000

We measured the invariant mass spectra of electron-positron pairs in the target rapidity region of 12-GeV p+A reactions. We have observed a significant difference in the mass spectra below the ω meson between p+C and p+Cu interactions. This difference indicates that the spectral shape of mesons is modified at normal nuclear-matter density.


©2001 The American Physical Society

URL: http://link.aps.org/abstract/PRL/v86/p5019
DOI: 10.1103/PhysRevLett.86.5019
PACS: 25.40.Ve, 14.40.Aq, 21.65.+f, 24.85.+p

* Present address: Center for Nuclear Study, Graduate School of Science, University of Tokyo, 7-3-1 Hongo, Tokyo 113-0033, Japan.Email address: ozawa@cns.s.u-tokyo.ac.jp
† Present address: ICEPP, University of Tokyo, 7-3-1 Hongo, Tokyo 113-0033, Japan.
‡ Present address: Physics Department, Graduate School of Science, Tohoku University, Sendai 980-8578, Japan.
§
** Present address: Fujitsu Corporation, 4-1-1, Kamikodanaka, Nakahara, Kawasaki, Kanagawa 211-8588, Japan.
†† Present address: RIKEN, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan.
‡‡ Present address: Xaxon Corporation, 1-3-19, Tanimachi, Chu-ou, Osaka, Japan.
Present address: Department of Physics, Osaka University, 1-1 Machikaneyama, Toyonaka, Osaka 560-0043, Japan.

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