Chiral dynamics of the S11(1535) and S11(1650) resonances revisited

Abstract

We analyze s-wave pion-nucleon scattering in a unitarized chiral effective Lagrangian including all dimension two contact terms. We find that both the S-11(1535) and the S-11(1650) are dynamically generated, but the S-31(1620) is not. We further discuss the structure of these dynamically generated resonances. (c) 2011 Elsevier B.V. All rights reserved.