Structure of the Λ(1405) baryon resonance from its large N_c behavior

We study the behavior with the number of colors (N_c) of the two poles associated to the Λ(1405) resonance obtained dynamically within the chiral unitary approach. The leading order chiral meson-baryon interaction manifests a nontrivial N_c dependence for SU(3) baryons, which gives a finite attractive interaction in some channels in the large N_c limit. As a consequence, the SU(3) singlet (K̅ N) component of the Λ(1405) survives in the large N_c limit as a bound state, while the other components dissolve into the continuum. The N_c dependence of the decay widths shows different behavior from the general counting rule for a qqq state, indicating the dynamical origin of the two poles for the Λ(1405) resonance.