PROPAGATOR AND PIONIC VERTEX OF A VIRTUAL NUCLEON

We discuss the πNN vertex in the case where one nucleon is virtual, as well as the related nucleon propagator. After summarizing results valid in any relativistic field theory which reproduces the observed πN scattering amplitudes in the P11 and S11 channels, we obtain explicit results from a generalized version of the Lee model. As expected from the general studies, our results show a strong enhancement of the proper form factor near the threshold energy for πN scattering, associated with a quenching of the propagator. Implications for the pion-exchange aspects of the NN interaction are briefly discussed. © 1979.