Dispersive chiral approach to meson-meson dynamics: Spectroscopy results for light scalars and precision studies

Abstract

Dispersive approaches provide model independent description of meson-meson scattering. We first review here the use of dispersion relations to obtain a model independent unitarization of Chiral Perturbation Theory amplitudes, that establish the existence of light scalar mesons and whose leading 1/N_c behavior suggest they ahve a non q q̅ dominant component. We also review the forward dispersion relation checks on conflicting experimental data and the resulting very precise pi pi scattering scattering amplitudes.