Photoproduction in an effective Lagrangian approach *

Abstract

Abstract A gauge-invariant model is constructed for the 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 K and 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 exchange are required to describe the most recently measured total cross-section data for from the CLAS Collaboration. Further analysis indicates that the interaction current dominates the reaction near the threshold as a result of gauge invariance. The t-channel K exchange contributes significantly, while the contributions from the t-channel exchange and s-channel nucleon exchange are ultimately negligible. The contributions from the s-channel exchange are found to be responsible for the bump structure shown in the CLAS total cross-section data above the center-of-mass energy GeV. The predictions of the differential cross sections for are presented and discussed, which can provide theoretical guidance for future experiments.