p-wave pion production from nucleon-nucleon collisions

We investigate $p$-wave pion production in nucleon-nucleon collisions up to next-to-next-to-leading order in chiral effective field theory. In particular, we show that it is possible to describe simultaneously the $p$-wave amplitudes in the $\mathit{pn}\ensuremath{\rightarrow}\mathit{pp}{\ensuremath{\pi}}^{\ensuremath{-}}$, $\mathit{pp}\ensuremath{\rightarrow}\mathit{pn}{\ensuremath{\pi}}^{+}$, $\mathit{pp}\ensuremath{\rightarrow}d{\ensuremath{\pi}}^{+}$ channels by adjusting a single low-energy constant accompanying the short-range operator that is available at this order. This study provides a nontrivial test of the applicability of chiral effective field theory to reactions of the type $\mathit{NN}\ensuremath{\rightarrow}\mathit{NN}\ensuremath{\pi}$.