Models of Meson-Baryon Reactions in the Nucleon Resonance Region

Abstract

It is shown that most of the models for analyzing meson-baryon reactions in the nucleon resonance region can be derived from a Hamiltonian formulation of the problem. An extension of the coupled-channel approach to include $\pi \pi N$ channel is briefly described and some preliminary results for the $N^{\ast }(1535)$ excitation are presented.

Comments: Latex 13 pages; to appear in the Proceedings of Workshop on the Physics of excited nucleons (NSTAR2004), Grenoble (France), March 24-27, 2004