The Structure of N(1535) in the Aspect of Chiral Symmetry

The N(1535) is the lowest lying nucleon resonance with J = 1 2 − , sitting just 50 MeV above the ηN threshold and having a large coupling to ηN in its decaying channel. The N(1535) has been studied in two aspects; one is based on mesonbaryon dynamics and the other on the symmetry of QCD. Since the N(1535) is a decaying resonance, the N(1535) may have large meson-baryon components. So the dynamics of mesons and baryons is important to understand the structure of the N(1535). In a more fundamental viewpoint of chiral symmetry of QCD, the N(1535) can be a candidate of the chiral partner of the ground state nucleon. The chiral partners form a set of particles which transform each other under the linear realization of the chiral transformation, like (ρ, a1) and (σ, π). It is an interesting question how to make these two aspects consistent with each other.