Pion-nuclear optical potential.s Wave scattering

Difficulties in the theoretical interpretation of thes wave phenomenological parameters of the pion-nuclear optical potential are considered. One-nucleon and two-nucleon parameters of such a potential for slow pion scattering are calculated. Uncertainties in the separation of the dispersive part of the potential into one- and two-nucleon contributions are discussed. It is shown that taking into account off-shell behaviour of the πN amplitude in the calculation of the two-nucleon parameters is important.