The Reaction $πN \to ππN$ at Threshold

Abstract

We consider the chiral expansion for the reaction $πN \to ππN$ in heavy baryon chiral perturbation theory. To order $M_π$ we derive novel low--energy theorems that compare favorably with recent determinations of the total cross sections for $π^+ p \to π^+ π^+ n$ and $π^- p \to π^0 π^0 n$.