Analytic Structure of the Triple-Regge Vertex

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Abstract
We study the triple-Regge, helicity-pole and related asymptotic behaviors of the six-line amplitude using the dual-resonance model (DRM) as a guide. We show that the triple-Regge vertex in the (DRM) can be expressed as a sum of four terms, which we interpret as exhibiting the allowed tree-like configurations of singularities in the asymptotic channel invariants. These four terms have counterparts in the helicity-pole limit where there exist several distinct terms with differing powers of the asymptotic variable, i.e., several different helicity poles. As an application we investigate the interesting property of the (DRM) that the triple-Regge or helicity-pole contribution to single-particle production at zero momentum transfer vanishes for trajectory intercepts near unity. We trace this effect to a nonsense zero. This suggests a mechanism for fulfilling one of the unitarity requirements for general six-line amplitudes. We discuss the possible generality of our results.