Recent progress in our understanding of infrared singularities of multi-parton amplitudes has shown that the simplest form of Regge factorization for high-energy gauge-theory amplitudes fails starting at next-to-next-to-leading logarithmic accuracy. We provide a framework to organize the calculation of parton amplitudes at leading power in t/s, in terms of factorizing and non-factorizing contributions. This allows us to give explicit expressions for the leading Reggeization-breaking terms in two-loop and three-loop quark and gluon amplitudes in QCD. In particular, using only infrared information, we recover a known non-factorizing, non-logarithmic double-pole contribution at two-loops, and we compute the leading non-factorizing single-logarithmic contributions at three loops.
@article{arxiv.1311.0304,
title = {High-energy QCD amplitudes at two loops and beyond},
author = {Vittorio Del Duca and Giulio Falcioni and Lorenzo Magnea and Leonardo Vernazza},
journal= {arXiv preprint arXiv:1311.0304},
year = {2015}
}