Annihilation into Channels with Strangeness and the OZI

Two-step mechanisms in the N N annihilation and their role in the OZI rule violating reactions are discussed. In particular the two meson rescattering mechanism for channel including all o -shell e ects is typically two orders of magnitude bigger than the OZI tree level expectation and explains the observed ratio =! in the annihilation at rest. The rates for the nal states including photons, ! and , can be explained in the vector dominance model. The observed rate for p p ! ! is suppressed due to destructive interference between the intermediate and ! states while the interference in p p! is required to be constructive leading to a large ratio = !.