M_(π) and N_c dependence of resonances form Unitarized Chiral Perturbation Theory

Abstract

We review our studies on the ρ and σ resonances properties derived from the Inverse Amplitude Method. In particular, we study the leading 1/N_c behavior of the resonances masses and widths and their evolution with changing m_(π). The 1/N_c expansion gives a clear definition of q̅ q states, which is neatly satisfied by the ρ but not by the σ, showing that its dominant component is not q̅q. The m_(π) dependence of the resonance properties is relevant to connect with lattice studies. We show that our predictions compare well with some lattice results and we find that the rho π πcoupling constant is m_π independent, in contrast with the σ π π coupling, that shows a strong m_π dependence.