Forward coherent ϕ-meson photoproduction from deuterons near threshold
/ Authors
We-Fu Chang, K. Horie, Suguru Shimizu, M. Miyabe, D. S. Ahn, D. S. Ahn, J. Ahn, H. Akimune, Y. Asano, S. Daté
and 56 more authors
H. Ejiri, S. Fukui, H. Fujimura, H. Fujimura, M. Fujiwara, M. Fujiwara, S. Hasegawa, K. Hicks, T. Hotta, K. Imai, T. Ishikawa, T. Iwata, Y. Kato, H. Kawai, Z. Kim, K. Kino, H. Kohri, N. Kumagai, P. Lin, S. Makino, T. Matsuda, T. Matsumura, N. Matsuoka, T. Mibe, Y. Miyachi, M. Morita, N. Muramatsu, N. Muramatsu, T. Nakano, M. Niiyama, M. Nomachi, Y. Ohashi, H. Ohkuma, T. Ooba, D. Oshuev, C. Rangacharyulu, A. Sakaguchi, T. Sasaki, P. Shagin, Y. Shiino, A. Shimizu, H. Shimizu, Y. Sugaya, M. Sumihama, M. Sumihama, Y. Toi, H. Toyokawa, A. Wakai, C. Wang, S. C. Wang, K. Yonehara, T. Yorita, M. Yoshimura, M. Yosoi, M. Yosoi, R. Zegers
/ Abstract
Abstract Differential cross sections and decay asymmetries for coherent ϕ -meson photoproduction from deuterons were measured for the first time at forward angles using linearly polarized photons at E γ = 1.5 – 2.4 GeV . This reaction offers a unique way to directly access natural-parity pomeron dynamics and gluon exchange at low energies. The cross sections at zero degrees increase with increasing photon energy. The decay asymmetries demonstrate a complete dominance of natural-parity exchange processes, showing that isovector unnatural-parity π -meson exchange is small. Nevertheless the deduced cross sections of ϕ -mesons from nucleons contributed by isoscalar t -channel exchange processes are not well described by the conventional pomeron model.
Journal: Physics Letters B