Chiral Dynamics and the $S_{11}(1535)$ Nucleon Resonance

Abstract

The $SU(3)$ chiral effective lagrangian at next-to-leading order is applied to the S-wave meson-baryon interaction in the energy range around the $\eta N$ threshold. Potentials are derived from this lagrangian and used in a coupled channel calculation of the $\pi N$, $\eta N$, $K\Lambda$, $K\Sigma$ system in the isospin-$1/2$, $l=0$ partial wave. Using the same parameters as obtained from a fit to the low energy $\overline{K}N$ data it is found that a quasi-bound $K\Sigma$-state is formed, with properties remarkably similar to the $S_{11}(1535)$ nucleon resonance. In particular, we find a large partial decay width into $\eta N$ consistent with the empirical data.

Comments: 9 pages, 6 postscript figures, e-mail: nkaiser@physik.tu-muenchen.de ; pbsiegel@csupomona.edu weise@physik.tu-muenchen.de