Analytic structure of the dual resonant amplitude with one nonplanar loop

Abstract

A rigorous treatment of the singularities of a dual resonant amplitude with one planar loop is given. The square root branchpoints of the unitarity cuts and the so called “pomeron” singularity are displayed explicitly. For this evaluation it is essential that the amplitude can be split into two parts, each with only one unitarity cut and trivial asymptotic properties in the opposite directions. An additional unphysical singularity restricting α 0 to less than 1 6 is found.