  Power-counting arguments are used to organize the interactions contributing
to the N N -> d pi, p n pi reactions near threshold. We estimate the
contributions from the three formally leading mechanisms: the Weinberg-Tomozawa
(WT) term, the impulse term, and the $\Delta$-excitation mechanism. Sub-leading
but potentially large mechanisms, including $S$-wave pion-rescattering, the
Galilean correction to the WT term, and short-ranged contributions are also
examined. The WT term is shown to be numerically the largest, and the other
contributions are found to approximately cancel. Similarly to the reaction p p
-> p p pi0, the computed cross sections are considerably smaller than the data.
We discuss possible origins of this discrepancy.

Nuclear Theory