On the structure of high-energy two-body non-diffractive reactions

Abstract

We consider the structure of two-body scattering amplitudes, concentrating on those reactions in which the "internal" quantum numbers exchanged correspond to the quantum numbers of a single particle, different from those of the vacuum. We compare conventional Regge-pole models (in which dips as a function of t are caused by "nonsense" factors) with our strong-cut model (in which dips are caused by a diffractive mechanism). In the conventional models, the systematics of the angular structure and determined by the nature of the exchange, as well as by the helicity structure and factorization. In the strong-cut model, the systematics of the angular structure are determined exclusively by the helicity structure of the amplitude (except for slight modification in the case of pion exchange, due to the proximity of the pion pole to the physical region); most important is the net helicity flip of the amplitude. We examine experimental data, particularly with regard to dips near -t(or -u) ~ 0.2 or 0.6, and near T = 0. It is found that whenever a distinction can be made, the strong-cut model is favored over the conventional models (even including cuts determined by conventional absorption models). Further experimental tests are proposed. Double-particle exchange processes, energy dependence, effects of t-channel unitarity and duality are discussed.