High-energy behaviour of a double discontinuity and the bare pomeron

Abstract

Abstract The high-energy behaviour of a double discontinuity of the six-point amplitude is studied in the dual-resonance model and in a hybrid Feynman-diagram model. This discontinuity imposes, through unitarity, a bound on the intercept of the bare-pomeron singularity. It is shown that in both models the ordinary Regge trajectories which couple to two-body amplitudes decouple from the discontinuity. The origin of this decoupling is discussed. The asymptotic behaviour of the double discontinuity is controlled by sister trajectories in the dual-resonance model, and by the genuine three-particle Regge poles in a Feynman-diagram model. Insofar as the intercepts of these trajectories are lower than those of the usual Regge poles there is no strong constraint on the pomeron.