Nuclear-Matter Modification of Decay Widths in the {phi}{yields}e{sup +}e{sup -} and {phi}{yields}K{sup +}K{sup -} Channels

• Published in: Physical review letters 2007-04, Vol.98 (15)
• Main Authors: Sakuma, F., Fukao, Y., Funahashi, H., Ishino, M., Kanda, H., Kitaguchi, M., Mihara, S., Miwa, K., Miyashita, T., Murakami, T., Nakura, T., Togawa, M., Yamada, S., Yoshimura, Y., Chiba, J., Ieiri, M., Sasaki, O., Sekimoto, M., Tanaka, K. H., En'yo, H.
• Format: Article
• Language: English
• Subjects: BREIT-WIGNER FORMULA; CARBON; COPPER; ELECTRON-POSITRON INTERACTIONS; ELECTRONS; GEV RANGE 10-100; KAONS MINUS; KAONS PLUS; MASS NUMBER; MASS SPECTRA; MODIFICATIONS; NUCLEAR MATTER; PAIR PRODUCTION; PARTICLE DECAY; PHI MESONS; PHYSICS OF ELEMENTARY PARTICLES AND FIELDS; POSITRONS; RELATIVISTIC RANGE
• ISSN: 0031-9007; 1079-7114
• DOI: 10.1103/PHYSREVLETT.98.152302

The invariant mass spectra of {phi}{yields}K{sup +}K{sup -} are measured in 12 GeV p+A reactions in order to search for the in-medium modification of {phi} mesons. The observed K{sup +}K{sup -} spectra are well reproduced by the relativistic Breit-Wigner function with a combinatorial background shape in three {beta}{gamma} regions between 1.0 and 3.5. The nuclear mass number dependence of the yields of the K{sup +}K{sup -} decay channel is compared to the simultaneously measured e{sup +}e{sup -} decay channel for carbon and copper targets. We parameterize the production yields as {sigma}(A)={sigma}{sub 0}A{sup {alpha}} and obtain {alpha}{sub {phi}}{sub {yields}}{sub K{sup +}}{sub K{sup -}}-{alpha}{sub {phi}}{sub {yields}}{sub e{sup +}}{sub e{sup -}} to be 0.14{+-}0.12. Limits are obtained for the partial decay widths of the {phi} mesons in nuclear matter.