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تسجيل مستخدم جديدPhotoproduction of $Lambda$ and $Sigma^{0}$ hyperons off protons with linearly polarized photons at $E_{gamma} = 1.5-3.0$ GeV
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We report the measurement of the $gamma p rightarrow K^{+}Lambda$ and $gamma p rightarrow K^{+}Sigma^{0}$ reactions at SPring-8. The differential cross sections and photon-beam asymmetries are measured at forward $K^{+}$ production angles using linearly polarized tagged-photon beams in the range of $E_{gamma}=1.5$--3.0 GeV. With increasing photon energy, the cross sections for both $gamma p rightarrow K^{+}Lambda$ and $gamma p rightarrow K^{+}Sigma^{0}$ reactions decrease slowly. Distinct narrow structures in the production cross section have not been found at $E_{gamma}=1.5$--3.0 GeV. The forward peaking in the angular distributions of cross sections, a characteristic feature of $t$-channel exchange, is observed for the production of $Lambda$ in the whole observed energy range. A lack of similar feature for $Sigma^{0}$ production reflects a less dominant role of $t$-channel contribution in this channel. The photon-beam asymmetries remain positive for both reactions, suggesting the dominance of $K^{*}$ exchange in the $t$ channel. These asymmetries increase gradually with the photon energy, and have a maximum value of +0.6 for both reactions. Comparison with theoretical predictions based on the Regge trajectory in the $t$ channel and the contributions of nucleon resonances indicates the major role of $t$-channel contributions as well as non-negligible effects of nucleon resonances in accounting for the reaction mechanism of hyperon photoproduction in this photon energy regime.
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