Measurement of Spin-Density Matrix Elements for ϕ-Meson Photoproduction from Protons and Deuterons Near Threshold
Chang, W. C. · Ahn, D. S. · Ahn, J. K. · Akimune, H. · Asano, Y. · Daté, S. · Ejiri, H. · Fujimura, H. · Fujiwara, M. · Fukui, S. · Hasegawa, H. · Hicks, K. · Horie, K. · Hotta, T. · Imai, K. · Ishikawa, T. · Iwata, T. · Kato, Y. · Kawai, H. · Kino, K. · Kohri, H. · Kumagai, N. · Lin, P. J. · Makino, S. · Matsuda, T. · Matsumura, T. · Matsuoka, N. · Mibe, T. · Miyabe, M. · Miyachi, Y. · Muramatsu, N. · Nakano, T. · Niiyama, M. · Nomachi, M. · Ohashi, Y. · Ohkuma, H. · Ooba, T. · Oshuev, D. S. · Rangacharyulu, C. · Sakaguchi, A. · Shagin, P. M. · Shiino, Y. · Shimizu, H. · Sugaya, Y. · Sumihama, M. · Toi, Y. · Toyokawa, H. · Uchida, M. · Wakai, A. · Wang, C. W. · Wang, S. C. · Yonehara, K. · Yorita, T. · Yoshimura, M. · Yosoi, M. · Zegers, R. G. T.
الأصل · EN
The LEPS/SPring-8 experiment made a comprehensive measurement of the spin-density matrix elements for γp → ϕp, γd → ϕp n and γd → ϕd at forward production angles. A linearly polarized photon beam at Eγ=1.6-2.4 GeV was used for the production of ϕ mesons. The natural-parity Pomeron exchange processes remains dominant nearthreshold. The unnatural-parity processes of pseudoscalar exchange is visible in the production from nucleons but is greatly reduced in the coherent production from deuterons. There is no strong Eγ-dependence, but 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.
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