Observation of <span class="aps-inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>ρ</mi><mi>/</mi><mi>ω</mi></math></span> Meson Modification in Nuclear Matter

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; Y. Yoshimura; J. Chiba; M. Ieiri; M. Nomachi; O. Sasaki; M. Sekimoto; K. H. Tanaka; H. Hamagaki

doi:10.1103/PhysRevLett.86.5019

Observation of $ρ / ω$ Meson Modification in Nuclear Matter

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, Y. Yoshimura, J. Chiba, M. Ieiri, M. Nomachi, O. Sasaki, M. Sekimoto, K. H. Tanaka, and H. Hamagaki

Phys. Rev. Lett. 86, 5019 – Published 28 May 2001

Abstract

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.

Received 14 November 2000

DOI:https://doi.org/10.1103/PhysRevLett.86.5019

Authors & Affiliations

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

^*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.