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

A gauge-invariant model is constructed for the $\gamma p \to K^+\Lambda(1690)$ reaction within a tree-level effective Lagrangian approach with the purpose to understand the underlying production mechanisms and to study the resonance contributions in this reaction. In addition to the $t$-channel $K$ and $K^{\ast }$ exchanges, the $s$-channel nucleon exchange, and the interaction current, the $s$-channel nucleon resonance exchanges are also included in constructing the reaction amplitudes to describe the data. It is found that the contributions from the $s$-channel $N(2570)5\mathrm{/}{2}^{-}$ exchange are required to describe the most recently measured total cross-section data for $\gamma p\to K^{+}\mathrm{\Lambda }(1690)$ from the CLAS Collaboration. Further analysis shows 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 $K$ exchange contributes significantly, while the contributions from the $t$-channel $K^{\ast }$ exchange as well as the $s$-channel nucleon exchange turn out to be negligible. The contributions from the $s$-channel $N(2570)5\mathrm{/}{2}^{-}$ 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\mathrm{.}Thepredictionsofthedifferentialcrosssectionsfor$\gamma p \to K^+\Lambda(1690)$ are shown and discussed, which can provide theoretical guidances for the future experiments.