N_c and m_π dependence of ρ and σ mesons from unitarized Chiral Perturbation Theory

Abstract

We review our work on the ρ and σ resonances 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/Nc expansion gives a clear definition of ¯qq states, which is neatly satisfied by the ρ but not by the σ, showing that its dominant component is not ¯qq. 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 ρππ coupling constant is mπ independent, in contrast with the σππ coupling, that shows a strong m_π dependence.