PI -N CHARGE EXCHANGE AND PI +-PI 0 SCATTERING AT LOW ENERGIES

Abstract π- N and π-π interactions near threshold are uniquely sensitive to the chiral symmetry breaking part of the strong interaction. The π- N σ-term value with its implications for nucleon quark structure and the recent controversy concerning the size of the scalar quark condensate have renewed the experimental interest in these two fundamental systems. We report new differential cross sections for the reaction π - p →π 0 n at 27.5 MeV pion incident kinetic energy, measured between θ CM = 0° and 55°. Our results are in excellentagreement with the existing comprehensive π N phase shift analysis. We also report on a Chew-Low analysis of exclusive π + p →π + π 0 p data at 260 MeV pion incident energy.