Nucleon recoil effect in the pion-nucleon interaction

We have studied the effect of nucleon recoil on pion-nucleon interaction in the $P$ wave using the dynamical model of Chew and Low which uses the nucleon pole terms as the driving mechanism. In general, the inclusion of recoil causes sizable reduction of the rescattering terms in every channel. In the $P33$ channel, this reduction is large enough to remove the resonance. This conclusion holds for any acceptable pion-nucleon coupling constant, and is independent of the choice of pion-nucleon form factor.