Photoproduction of Λ and Σ0 hyperons off protons with linearly polarized photons at Eγ=1.5-3.0 GeV

We report the measurement of the γp→K+Λ and γp→K+Σ0 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 Eγ=1.5-3.0 GeV. With increasing photon energy, the cross sections for both γp→K+Λ and γp→K+Σ0 reactions decrease slowly. Distinct narrow structures in the production cross section have not been found at Eγ=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 Λ in the whole observed energy range. A lack of similar feature for Σ0 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.