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.
|ジャーナル||Modern Physics Letters A|
|出版ステータス||Published - 2008 9月 30|
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