Elastic, charge exchange, and inelastic p-barp cross sections in the optical model

The optical model of antiproton-proton scattering is examined critically. We show that the addition of an attractive real part to the annihilation potential allows one to reduce the imaginary part and to improve the fit to the data. However, the absorptive component must be still rather strong and also have a fairly large range. Such features are difficult to understand in terms of naive direct channel meson exchange processes. We confirm also in the local optical model that no narrow structures can survive annihilation, unless they lie very close to threshold. The optical model we propose, with the realistic Paris potential for the long range t-channel part, provides an effective description of background N-barN scattering