Nuclear-matter modification of decay widths in the $ϕ\to e^{+}e^{-}$ and $ϕ\to K^{+}K^{-}$ channels

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

Nuclear-matter modification of decay widths in the $ϕ\to e^{+}e^{-}$ and $ϕ\to K^{+}K^{-}$ channels

Authors

Description

The invariant mass spectra of $ϕ\to K^{+}K^{-}$ are measured in 12 GeV $p+A$ reactions in order to search for the in-medium modification of $ϕ$ mesons. The observed $K^{+}K^{-}$ spectra are well reproduced by the relativistic Breit-Wigner function with a combinatorial background shape in three $βγ$ regions between 1.0 and 3.5. The nuclear mass-number dependence of the yields of the $K^{+}K^{-}$ decay channel is compared to the simultaneously measured $e^{+}e^{-}$ decay channel for carbon and copper targets. We parameterize the production yields as $σ(A) = σ_0 \times A^α$ and obtain $α_{ϕ\to K^+K^-} - α_{ϕ\to e^+e^-}$ to be 0.14 $\pm$ 0.12. Limits are obtained for the partial decay widths of $ϕ$ mesons in nuclear matter.
5 pages, 4 figures