2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/205217We use the one-loop Chiral Perturbation Theory pion-pion scattering amplitude and dispersion theory in the form of the inverse amplitude method, to study the quark mass dependence of the two lightest resonances of the strong interactions, the f_0(600) (sigma) and the rho-meson. As main results we find that the rho-pion-pion coupling constant is almost quark mass independent and that the rho mass shows a smooth quark mass dependence while that of the sigma shows a strong non-analyticity. These findings are important for studies of the meson spectrum on the lattice.Final version to appear in Phys. Rev. Lett. References added and typos corrected. 4 pages, three figuresHigh Energy Physics - PhenomenologyHigh Energy Physics - Latticetext