Associated photoproduction ofK+mesons off protons within a coupled-channelsK-matrix approach

Abstract

We investigate the $p(\ensuremath{\gamma},{K}^{+})\ensuremath{\Lambda}$ and $p(\ensuremath{\gamma},{K}^{+}){\ensuremath{\Sigma}}^{0}$ reactions within a coupled-channels effective-Lagrangian method that is based on the $\mathsf{K}$-matrix approach. The two-body final channels included are $\ensuremath{\pi}N$, $\ensuremath{\eta}N$, $\ensuremath{\phi}N$, $\ensuremath{\rho}N$, $\ensuremath{\gamma}N$, $K\ensuremath{\Lambda}$, and $K\ensuremath{\Sigma}$. Nonresonant 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 ${S}_{11}(1535)$, ${S}_{11}(1650)$, ${S}_{31}(1620)$, ${P}_{11}(1440)$, ${P}_{11}(1710)$, ${\mathrm{P}}_{13}(1720)$, ${P}_{33}(1232)$, ${P}_{33}(1600)$, ${\mathrm{D}}_{13}(1520)$, ${D}_{13}(1700)$, and ${D}_{33}(1700)$ are included explicitly in the calculations. With a single parameter set that was derived earlier from our analysis of $\ensuremath{\eta}$-meson photoproduction, the model describes all the available cross-section and polarization data of the SAPHIR Collaboration well for the two investigated channels. The description of the data from the CLAS Collaboration, however, is not of the same quality. In contrast to some previous studies, we do not find any compelling need to include a ${D}_{13}$ state with a mass of about $2.0$ GeV to reproduce the data for the $p(\ensuremath{\gamma},{K}^{+})\ensuremath{\Lambda}$ reaction at photon energies corresponding to the invariant mass around $1.9$ GeV.