Generalized Isobar Model, and the Pionic Form Factor of the Nucleon

It is pointed out that in a simple model in which the isobar is excited by a virtual pion, the deviations can be understood in a simple way in terms of the decreasing probability of isobar excitation for increasing fourmomenta transfer between colliding nucleons. This model predicts moderately well-defined peaks in the inelastic spectrum, corresponding to the various nucleon isobars. These isobars are in turn considered to correspond to the peaks in the pi -N cross section; the first three correspond to isobar masses M/sub 1/' = 1.23 Bev, M/sub 2/' = 1.52 Bev, and M/sub 3/' = 1.67 Bev. The predominant features of the experimental results are outlined. (B.O.G.)