The associated photoproduction of K+ meson off proton within a coupled-channels K-matrix approach

We investigate the p(gamma,K+)Lambda and p(gamma,K+)Sigma^0 reactions within a coupled-channels effective-Lagrangian method which is based on the K-matrix approach. The two-body final channels included are pi-N, eta-N, phi-N, rho-N, gamma-N, K-Lambda, and K-Sigma. Non-resonant meson-baryon interactions are included in the model via nucleon intermediate states in the s- and u-channels and meson exchanges in the t-channel amplitude and the u-channel resonances. The nucleon resonances S11 (1535), S11 (1650), S31 (1620), P11 (1440), P11 (1710), P13 (1720), P33 (1232), P33 (1600), D13 (1520), D13 (1700), and D33 (1700) are included explicitly in the calculations. With a single parameter set which was derived earlier from our analysis of the eta meson photoproduction, the model describes well all the available cross section and polarization data of the SAPHIR collaboration for the two investigated channels. The description of the data of the CLAS collaboration, however, is not of the same quality. In contrast to some previous studies, we do not find any compelling need for including a D13 state with mass of around 2.0 GeV in order to reproduce the data for the p(gamma,K+)Lambda reaction at photon energies corresponding to the invariant mass around 1.9 GeV.