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 γp⃗K⁺Λ in several isobaric models. These models typically include Born terms, K^* and K₁ 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_KΛN and g_KΣN, 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.