First measurement of coherent ϕ-meson photoproduction from 4He near thresholdстатья
Статья опубликована в высокорейтинговом журнале
Информация о цитировании статьи получена из
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Статья опубликована в журнале из списка Web of Science и/или Scopus
Дата последнего поиска статьи во внешних источниках: 10 августа 2018 г.
Аннотация:The differential cross sections and decay angular distributions for coherent ϕ-meson photoproduction from helium-4 are measured for the first time at forward angles with linearly polarized photons in the energy range Eγ=1.685–2.385GeV. Thanks to the target with spin-parity JP=0+, unnatural-parity exchanges are absent, and thus natural-parity exchanges can be investigated clearly. The decay asymmetry with respect to photon polarization is shown to be very close to the maximal value. This ensures the strong dominance (>94%) of natural-parity exchanges in this reaction. To evaluate the contribution from natural-parity exchanges to the forward cross section (θ=0∘) for the γp→ϕp reaction near threshold, the energy dependence of the forward cross section (θ=0∘) for the γ4He→ϕ4He reaction is analyzed. The comparison to γp→ϕp data suggests that enhancement of the forward cross section arising from natural-parity exchanges and/or destructive interference between natural-parity and unnatural-parity exchanges is needed in the γp→ϕp reaction near threshold.