Dynamical coupled-channel approach to hadronic and electromagnetic production of kaon-hyperon on the proton

Abstract

A dynamical coupled-channel formalism for processes $\pi N\to KY$ and $\gamma N\to KY$ is presented which provides a comprehensive investigation of recent data on the $\gamma p\to K^{+}\Lambda$ reaction. The non-resonant interactions within the subspace $KY\oplus \pi N$ are derived from effective Lagrangians, using a unitary transformation method. The calculations of photoproduction amplitudes are simplified by casting the coupled-channel equations into a form such that the empirical $\gamma N\to \pi N$ amplitudes are input and only the parameters associated with the $KY$ channel are determined by performing ${\chi }^2$-fits to all of the available data for ${\pi }^{-}p\to K^{\circ }\Lambda ,K^{\circ }{\Sigma }^{\circ }$ and $\gamma p\to K^{+}\Lambda$. Good agreement between our models and those data are obtained. In the fits to $\pi N\to KY$ channels, most of the parameters are constrained within $\pm 20$ of the values given by the Particle Data Group and/or quark model predictions, while for $\gamma p\to K^{+}\Lambda$ parameters, ranges compatible with broken $SU(6)\otimes O(3)$ symmetry are imposed. The main reaction mechanisms in $K^{+}\Lambda$ photoproduction are singled out and issues related to newly suggested resonances $S_{11}$, $P_{13}$, and $D_{13}$ are studied. Results illustrating the importance of using a coupled-channel treatment are reported. Meson cloud effects on the $\gamma N\to N^{\ast }$ transitions are also discussed.

Accepted Physical Review C