Measurement of spin-density matrix elements for φ-meson photoproduction from protons and deuterons near threshold
/ Authors
We-Fu Chang, D. S. Ahn, D. S. Ahn, J. Ahn, H. Akimune, Y. Asano, S. Dat'e, H. Ejiri, H. Fujimura, M. Fujiwara
and 48 more authors
M. Fujiwara, S. Fukui, S. Hasegawa, K. Hicks, K. Horie, T. Hotta, K. Imai, Takatsugu Ishikawa, Takahiro Iwata, Y. Kato, H. Kawai, K. Kino, H. Kohri, N. Kumagai, P. Lin, S. Makino, T. Matsuda, T. Matsumura, N. Matsuoka, T. Mibe, M. Miyabe, Y. Miyachi, N. Muramatsu, T. Nakano, M. Niiyama, M. Nomachi, Y. Ohashi, H. Ohkuma, T. Ooba, D. Oshuev, C. Rangacharyulu, A. Sakaguchi, P. Shagin, Y. Shiino, H. Shimizu, Y. Sugaya, M. Sumihama, Y. Toi, H. Toyokawa, M. Uchida, A. Wakai, Chun-Chieh Wang, S. C. Wang, K. Yonehara, T. Yorita, M. Yoshimura, M. Yosoi, R. Zegers
/ Abstract
The LEPS/SPring-8 experiment made a comprehensive measurement of the spin-density matrix elements for gammap->phip, gammad->phipn, and gammad->phid at forward production angles. A linearly polarized photon beam at E{sub g}amma=1.6-2.4 GeV was used for the production of phi mesons. The natural-parity Pomeron exchange processes remain dominant near threshold. The unnatural-parity processes of pseudoscalar exchange is visible in the production from the nucleons but is greatly reduced in the coherent production from deuterons. There is no strong E{sub g}amma dependence, but there is some dependence on momentum transfer. A small but finite value of the spin-density matrix elements reflecting helicity-nonconserving amplitudes in the t-channel is observed.
Journal: Physical Review C