Pseudovector versus pseudoscalar coupling in kaon photoproduction reexamined

The question of pseudovector versus pseudoscalar coupling schemes for the kaon-hyperon-nucleon interaction is reexamined for the reaction gamma p-->K(+)Lambda in several isobaric models. These models typically include Born terms, K* and K-l exchanges in the t channel, and a few different combinations of spin-1/2 baryon resonances in the s and u channels. The coupling constants are obtained by fitting to a large data set. We find that both pseudoscalar and pseudovector couplings can allow for a satisfactory description of the present database. The resulting coupling constants, g(K Lambda N) and g(K Sigma N), in the pseudovector coupling scheme are smaller than those predicted using flavor SU(3) symmetry, but consistent with the values obtained in a QCD sum rule calculation.