Origin of resonances in the chiral unitary approach
  We study the origin of the resonances associated with pole singularities of the scattering amplitude in the chiral unitary approach. We propose a "natural renormalization" scheme using the low-energy interaction and the general principle of the scattering theory. We develop a method to distinguish dynamically generated resonances from genuine quark states [Castillejo-Dalitz-Dyson (CDD) poles] using the natural renormalization scheme and phenomenological fitting. Analyzing physical meson-baryon scatterings, we find that the Lambda(1405) resonance is largely dominated by the meson-baryon molecule component. In contrast, the N(1535) resonance requires a sizable CDD pole contribution, while the effect of the meson-baryon dynamics is also important. 
Tetsuo Hyodo (1 and 2), Daisuke Jido, (2) Atsushi Hosaka (3), ((1) TU   Muenchen, (2) YITP, Kyoto Univ., (3) RCNP, Osaka Univ.)