Nucleon and Δ resonances in γn→K+Σ− photoproduction

Abstract

The most recent data on beam asymmetries $\mathrm{\ensuremath{\Sigma}}$ and beam-target asymmetries $E$ from the CLAS Collaboration, together with the previous data on differential cross sections and beam asymmetries from the CLAS and LEPS Collaborations, for the $\ensuremath{\gamma}n\ensuremath{\rightarrow}{K}^{+}{\mathrm{\ensuremath{\Sigma}}}^{\ensuremath{-}}$ reaction are studied based on an effective Lagrangian approach in the tree-level Born approximation. The $t$-channel $K$ and ${K}^{*}(892)$ exchanges, the $u$-channel $\mathrm{\ensuremath{\Sigma}}$ exchange, the interaction current, and the exchanges of $N$, $\mathrm{\ensuremath{\Delta}}$, and their excited states in the $s$ channel are considered in constructing the reaction amplitudes to describe the available experimental data. The reaction mechanisms of $\ensuremath{\gamma}n\ensuremath{\rightarrow}{K}^{+}{\mathrm{\ensuremath{\Sigma}}}^{\ensuremath{-}}$ are analyzed, and the associated resonances' parameters are extracted. The numerical results show that the $\mathrm{\ensuremath{\Delta}}$ exchange and the $N(1710)1/{2}^{+}$, $N(1880)1/{2}^{+}$, $N(1900)3/{2}^{+}$, and $\mathrm{\ensuremath{\Delta}}(1920)3/{2}^{+}$ resonance exchanges in the $s$ channel dominate the $\ensuremath{\gamma}n\ensuremath{\rightarrow}{K}^{+}{\mathrm{\ensuremath{\Sigma}}}^{\ensuremath{-}}$ reaction in the lower energy region, and the $t$-channel ${K}^{*}(892)$ exchange plays a crucial role at forward angles in the higher energy region.