Impulse approximation in the np → dπ0 reaction reexamined

The impulse approximation (one-body operator) in the np -> d pi(0) reaction is reexamined with emphasis on the issues of reducibility and recoil corrections. An inconsistency when one-pion exchange is included in the production operator is demonstrated and then resolved via the introduction of "wave function corrections" which nearly vanish for static nucleon propagators. Inclusion of the recoil corrections to the nucleon propagators is found to change the magnitude and sign of the impulse production amplitude, worsening agreement with the experimental cross section by similar to 30%. A cutoff is used to account for the phenomenological nature of the external wave functions and is found to have a significant impact for Lambda less than or similar to 2.5 GeV.