Chiral Three-Nucleon Forces from p-wave Pion Production

Production of p-wave pions in nucleon-nucleon collisions is studied according to an improved power counting that embodies the constraints of chiral symmetry. Contributions from the first two non-vanishing orders are calculated. We find reasonable convergence and agreement with data for a spin-triplet cross section in $pp\to pp{\pi }^0$,with no free parameters. Agreement with existing data for a spin-singlet cross section in $pp\to pn{\pi }^{+}$ constrains a short-range operator shown recently to contribute significantly to the three-nucleon potential.