Chiral symmetry for positive and negative parity nucleons

Chiral properties of positive and negative parity nucleons 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 assignments, theoretical as well as phenomenological consequences are investigated. We find that the nucleon mass in the chirally restored phase is the key quantity to determine the meson-nucleon couplings and the axial charges of the nucleons. We also discuss the role of spontaneous chiral symmetry breaking in the mass splitting between the positive and negative parity nucleons. (C) 2000 Elsevier Science B.V. All rights reserved.