Partial decay widths of the φ into e+e- and K+K- pairs in 12 GeV p + a reactions at KEK-PS E325

F. Sakuma, 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, R. Muto, T. Nakura, M. Naruki, K. Ozawa, O. Sasaki, M. SekimotoT. Tabaru, K. H. Tanaka, M. Togawa, S. Yamada, S. Yokkaichi, Y. Yoshimura

Research output: Contribution to journalArticlepeer-review


The experiment KEK-PS E325 measured e+e- and K +K- pairs produced in 12 GeV p + A reactions, in order to search for in-medium modification of vector mesons. In the e+e - spectra, a significant excess on the low-mass side of the φ-meson peak is observed in the very low βγ (= p/m) region of the copper target data. On the other hand when the velocity of φ mesons is higher or a smaller target, carbon, is employed, the observed φ-meson shapes are consistent with the expected shape in vacuum, both in the e +e- and K+K- spectra. We have also compared the nuclear mass number dependence of φ-meson production between the e+e- and K+K- decay channels. Using these results, the first experimental limits are obtained for in-medium broadening of the partial decay widths.

Original languageEnglish
Pages (from-to)2401-2404
Number of pages4
JournalModern Physics Letters A
Issue number27-30
Publication statusPublished - 2008 Sep 30
Externally publishedYes


  • KK decay
  • ee decay
  • φ-meson

ASJC Scopus subject areas

  • Nuclear and High Energy Physics
  • Astronomy and Astrophysics
  • Physics and Astronomy(all)


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