Chiral Symmetry for Positive and Negative Parity Nucleons

Abstract

Chiral properties of positive and negative parity nucleons, N and N*$, are studied from the viewpoint of chiral symmetry. Two possible ways to assign chiral transformations to the negative parity nucleon are considered. Using linear sigma models based on the two chiral realizations, theoretical as well as phenomenological consequences of the two different assignments are investigated. We find that the nucleon mass in the chiral restored phase is the key quantity to determine the meson-nucleon couplings and the axial charges of nucleons. We also discuss the role of chiral symmetry breaking in the mass splitting of N and N* in the two sigma models.