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
Department of Physics, Kyoto University, Kitashirakawa Sakyo-ku, Kyoto 606-8502, Japan.
Phys Rev Lett. 2007 Apr 13;98(15):152302. doi: 10.1103/PhysRevLett.98.152302.
The invariant mass spectra of phi-->K+K- are measured in 12 GeV p+A reactions in order to search for the in-medium modification of phi mesons. The observed K+K- spectra are well reproduced by the relativistic Breit-Wigner function with a combinatorial background shape in three betagamma 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 sigma(A)=sigma0Aalpha and obtain alphaphi-->K+K- -alphaphi-->e+e- to be 0.14+/-0.12. Limits are obtained for the partial decay widths of the phi mesons in nuclear matter.
在12 GeV质子与原子核（p+A）反应中测量了φ介子衰变到K⁺K⁻的不变质量谱，以探寻φ介子在介质中的修正情况。在1.0至3.5的三个βγ区域内，相对论性布赖特-维格纳函数与组合背景形状能很好地再现观测到的K⁺K⁻谱。将K⁺K⁻衰变道产额的核质量数依赖性与同时测量的碳和铜靶的e⁺e⁻衰变道进行了比较。我们将产额参数化为σ(A)=σ₀A^α，得出α(φ→K⁺K⁻) - α(φ→e⁺e⁻)为0.14±0.12。得到了φ介子在核物质中的部分衰变宽度的限制。
