Backward elastic p-d scattering and nucleon excitation

We calculate the backward differential cross section for elastic p-d scattering from a double triangle diagram including as input the π-N amplitude obtained from the phase shift data. The theoretical calculations are compared with the recent high energy p-d scattering experiments, and we find the energy dependence of Barry's adjusting parameter, zeta, which must be independent of the energy, so we shall emphasize the necessity of the contribution of other intermediate states from π-N. We also discuss the relation between our model and the N* exchange model in connection with the duality. (auth.)