Photopion production with nonresonantΔ33background interference

The nonresonant interference effects in the (3,3) channel proposed by Olsson are incorporated into a full amplitude that describes photopion production from a single nucleon. The reactions $p(\gamma , {\pi }^{+})n$, $n(\gamma , {\pi }^{-})p$, and $p(\gamma , {\pi }^0)p$ are all well described by this amplitude. The charged pion production cross sections obtained with Olsson's effects are similar to those calculated by Blomqvist and Laget, but the new amplitude has the added feature of also describing neutral pion production. Asymmetry parameters calculated with the new and Blomqvist and Laget amplitudes are compared with experiment for the cases where either the incident photon, the target, or final state baryon are polarized; the new photopion production amplitude provides a good description of these experiments.