Nucleon and ? resonances in ?n ? K + ?- photoproduction

The most recent data on beam asymmetries ?? 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 ??n ??? K+????? 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 ?? exchange, the interaction current, and the exchanges of N, ??, 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 ??n ??? K+????? are analyzed, and the associated resonances??? parameters are extracted. The numerical results show that the ?? exchange and the N(1710)1/2+, N(1880)1/2+, N(1900)3/2+, and ??(1920)3/2+ resonance exchanges in the s channel dominate the ??n ??? K+????? 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.