Contributions of box diagrams and $Δ(1940)$ resonance to $K^0Σ^+$ photoproduction

Abstract

We study first the box-diagram contribution to the γp → K 0 Σ + process to understand the anomaly of the kaon photoproduction cross section from CBELSA/TAPS experiment at Electron Stretcher Accelerator (ELSA), where the imaginary part of the scattering amplitude from the boxdiagrams is calculated by using Cutkosky's rules in the on-shell approximation while the real part of the amplitude is derived by dispersion relation calculations. Together with the results of the K-MAID model, the contribution of the box-diagrams fails to provide the sudden drop of the differential cross-section between the K * Λ and K * Σ thresholds. In addition, we include the ∆(1940) resonance in the process to complete the description of the differential cross-section. Combining the contributions from the K-MAID model, the box-diagrams and the ∆(1940) resonance, we have obtained the theoretical differential cross-section the γp → K 0 Σ + process, which is compatible with the CBELSA/TAPS experimental data.