Chiral Lagrangian treatment of pi eta scattering

Abstract

We study pi eta scattering in a model which starts from the tree diagrams of a non-linear chiral Lagrangian including appropriate resonances. Previously, models of this type were applied to pi pi and pi K scattering and were seen to require the existence of light scalar sigma(560) and kappa(900) mesons and to be consistent with the f0(980). The present calculation extends this to include the a0(980), thereby completing a possible nonet of light scalars, all ``seen'' in the same manner. We note that, at the initial level, the pi eta channel is considerably cleaner than the pi pi and pi K channels for the study of light scalars. This is because the large competing effects of vector meson exchange and ``current-algebra'' contact terms are absent. The simplicity of this channel enables us to demonstrate the closeness of our exactly crossing symmetric amplitude to a related exactly unitary amplitude. The calculation is also extended to higher energies in order to let us discuss the role played by the a0(1450) resonance.