PION-NUCLEON SCATTERING AT LOW ENERGIES

We study pion-nucleon scattering at tree level with a chiral Lagrangia n of pions, nucleons, and Delta isobars using a K-matrix unitarization procedure. Evaluating the scattering amplitude to order Q(2), where Q is a generic small momentum scale, we obtain a good fit to the experi mental phase shifts for pion center-of-mass kinetic energies up to 50 MeV. The fit can be extended to 150 MeV when we include the order-Q(3) contributions. Our results are independent-of the off-shell Delta par ameter.