Energy-independent separable potentials for the pion-nucleon P33 channel

We have constructed three rank-one energy-independent separable potentials for the pion-nucleon P33 channel which reproduce the scattering volume and phase shift up to 350 MeV. The amplitudes were calculated from these potentials using the Blankenbecler-Sugar equation approach and are appropriate for relativistic three-body calculations of the πNN system. An interesting feature of resulting potentials is the appearance of two very different ranges in each. The low-momentum parts of the different potentials are essentially the same but there are significant differences in their high-momentum behavior. Information from NN pion-production supports the two-range feature of these potentials and favors one of the potentials over the others. NUCLEAR REACTIONS N(π,π)N; separable potentials for P33 channel; calculated δ(E), E=0-350 MeV.