UNITARIZED CHIRAL PERTURBATION-THEORY FOR ELASTIC PION-PION SCATTERING

The low-energy two-pion elastic scattering is calculated within the framework of the one-loop chiral perturbation theory in combination with the Padé approximant method for the partial wave amplitudes. Elastic unitarity is satisfied to all orders. It is shown that the experimental data below 900 MeV can be described in terms of two independent parameters and that the chiral symmetry limit of massless pions gives a good description of the data above 350 MeV. With chiral symmetry breaking (finite pion mass) our calculation yields a ρ{variant} width of 155 MeV and an S-wave I=0 scattering length of a0=0.27mπ-1, in good agreement with experimental data. These results demonstrate the validity of our method as applied to the strongly interacting Higgs sector. © 1990.