Suppression of Pi NN* Coupling and Chiral Symmetry

Meson-baryon couplings between positive and negative parity nucleons are investigated using two point correlation functions in the soft meson and the chiral limit. We find that the pi NN* coupling vanishes due to chiral symmetry, while the eta NN* coupling remains finite. We perform an analysis based on the algebraic method for SU(2) chiral symmetry, and find that nucleon axial charges play an essential role for vanishing coupling constants. For an illustration, we construct sigma models with N and N*, where we discuss their properties from the view point of the chiral symmetry. We also discuss N and N* in the viewpoint of chiral partner.