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arXiv · 1006.4197

Measurement of Spin-Density Matrix Elements for $\phi$-Meson Photoproduction from Protons and Deuterons Near Threshold

W. C. Chang·D. S. Ahn·J. K. Ahn·H. Akimune·Y. Asano·S. Daté·H. Ejiri·H. Fujimura·M. Fujiwara·S. Fukui·H. Hasegawa·K. Hicks·K. Horie·T. Hotta·K. Imai·T. Ishikawa·T. Iwata·Y. Kato·H. Kawai·K. Kino·H. Kohri·N. Kumagai·P. J. 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. S. Oshuev·C. Rangacharyulu·A. Sakaguchi·P. M. Shagin·Y. Shiino·H. Shimizu·Y. Sugaya·M. Sumihama·Y. Toi·H. Toyokawa·M. Uchida·A. Wakai·C. W. Wang·S. C. Wang·K. Yonehara·T. Yorita·M. Yoshimura·M. Yosoi·R. G. T. Zegers
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Abstract

The LEPS/SPring-8 experiment made a comprehensive measurement of the spin-density matrix elements for $\gamma p \to \phi p$, $\gamma d \to \phi p n$ and $\gamma d \to \phi d$ at forward production angles. A linearly polarized photon beam at $E_{\gamma}$=1.6-2.4 GeV was used for the production of $\phi$ 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 $E_{\gamma}$-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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W. C. Chang, D. S. Ahn, J. K. Ahn, H. Akimune, Y. Asano, S. Daté, H. Ejiri, H. Fujimura, M. Fujiwara, S. Fukui, H. Hasegawa, K. Hicks, K. Horie, T. Hotta, K. Imai, T. Ishikawa, T. Iwata, Y. Kato, H. Kawai, K. Kino, H. Kohri, N. Kumagai, P. J. 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. S. Oshuev, C. Rangacharyulu, A. Sakaguchi, P. M. Shagin, Y. Shiino, H. Shimizu, Y. Sugaya, M. Sumihama, Y. Toi, H. Toyokawa, M. Uchida, A. Wakai, C. W. Wang, S. C. Wang, K. Yonehara, T. Yorita, M. Yoshimura, M. Yosoi, R. G. T. Zegers. 2010-06-22. Measurement of Spin-Density Matrix Elements for $\phi$-Meson Photoproduction from Protons and Deuterons Near Threshold. https://doi.org/10.1103/physrevc.82.015205

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