THE REACTION PI-N-]PI-PI-N ABOVE-THRESHOLD IN CHIRAL PERTURBATION-THEORY

Single pion production off nucleons is studied in the framework of rel ativistic baryon chiral perturbation theory at tree level with the inc lusion of the terms from the dimension two effective pion-nucleon Lagr angian. The five appearing low-energy constants are fixed from pion-nu cleon scattering data. Despite the simplicity of the approach, most of the existing data for total and differential cross sections as well a s for the angular correlation functions for incoming pion kinetic ener gies up to 400 MeV can be satisfactorily described. (C) 1997 Elsevier Science B.V.