Experimental Signature of Medium Modifications for rho and omega Mesons in the 12 GeV p + A Reactions

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

Experimental Signature of Medium Modifications for rho and omega Mesons in the 12 GeV p + A Reactions

Authors

Description

The invariant mass spectra of e+e- pairs produced in 12-GeV proton-induced nuclear reactions are measured at the KEK Proton-Synchrotron. On the low-mass side of the omega meson peak, a significant enhancement over the known hadronic sources has been observed. The mass spectra, including the excess, are well reproduced by a model that takes into account the density dependence of the vector meson mass modification, as theoretically predicted.
4 pages, 3 figures, Version accepted for Physical Review Letter