Scalar Mesons and Chiral Dynamics

Abstract

We discuss scalar mesons properties on the light of chiral dynamics. Considering them as the chiral partners of pseudo-scalar mesons we propose an explanation to their unusual properties based on non-trivial vacuum effects coming from the interplay between spontaneous breaking of chiral symmetry and the violation of $U_A(1)$ symmetry by instantons. Including vector mesons as external sources we work out predictions for radiative decays of vector mesons and compare some of them with recent experimental results from high luminosity $\Phi$ factories.

Comments: 9 pages, invited talk to the VIII Mexican Workshop on Particles and Fields, Zacatecas, Mexico, Nov. 14-20, 2001