Complex Angular Momentum and Infinite Helicity Sums. II
Abstract
We discuss some features of the continuation to complex total angular momentum of the threeparticle discontinuity of a "double box" Feynman diagram. A solution of this problem implies that the discontinuity satisfies the bound required by Carlson's theorem. We conclude that for this to be possible the phasespace integral has to be organized in two separate pieces. Also, the partialwave amplitudes have to be broken into two separate pieces, each piece being given by a FroissartGribov contour around a singularity of the helicity amplitude. This splitting of the partialwave amplitude introduces an extra singularity, but this does not contribute to the final expression.
 Publication:

Physical Review
 Pub Date:
 July 1968
 DOI:
 10.1103/PhysRev.171.1517
 Bibcode:
 1968PhRv..171.1517W