Global analysis of πN→ππNdata near threshold and chiral-symmetry breaking

An analysis has been made of all available data near threshold for the reactions πN→ππN in terms of isospin amplitudes. The experiments for different channels are found to be consistent with each other and with the chiral-symmetry-breaking model of Olsson and Turner. The analysis yields values for the ππ scattering lengths which are in good agreement with a calculation based on the Weinberg ππ interaction corrected for the effects of the ${\mathit{f}}_0$(975) scalar meson.