Photoproduction ${ \boldsymbol\gamma \boldsymbol p \boldsymbol \to {\boldsymbol K}^+\boldsymbol\Lambda{\boldsymbol{(1690)}} }$ in an effective Lagrangian approach

Abstract：

A gauge-invariant model is constructed for the $ \gamma p \to K^+\Lambda(1690) $ reaction within a tree-level effective Lagrangian approach to understand the underlying production mechanisms and study the resonance contributions in this reaction. In addition to the t-channel Kand $ K^\ast $ exchanges, s-channel nucleon exchange, and interaction current, the s-channel nucleon resonance exchanges are included in constructing the reaction amplitudes to describe the data. It is found that the contributions from the s-channel $ N(2570)5/2^- $ exchange are required to describe the most recently measured total cross-section data for $ \gamma p \to K^+\Lambda(1690) $ from the CLAS Collaboration. Further analysis indicates that the interaction current dominates the $ \gamma p \to K^+\Lambda(1690) $ reaction near the threshold as a result of gauge invariance. The t-channel Kexchange contributes significantly, while the contributions from the t-channel $ K^\ast $ exchange and s-channel nucleon exchange are ultimately negligible. The contributions from the s-channel $ N(2570)5/2^- $ exchange are found to be responsible for the bump structure shown in the CLAS total cross-section data above the center-of-mass energy $ W \approx 2.7 $ GeV. The predictions of the differential cross sections for $ \gamma p \to K^+\Lambda(1690) $ are presented and discussed, which can provide theoretical guidance for future experiments.