paper

Infrared Singularities of Scattering Amplitudes and NLL Resummation for -Jet Processes

arXiv:1908.11379 · doi:10.1007/JHEP01(2020)025

Abstract

We revisit the multi-loop structure of the anomalous-dimension matrix governing the infrared divergences of massless -particle scattering amplitudes in non-abelian gauge theories. In particular, we derive its most general form at four-loop order, significantly simplifying corresponding expressions given previously. By carefully reevaluating the constraints imposed by two-particle collinear limits, we find that at four-loop order color structures involving , the symmetrized trace of four group generators, appear along with cusp logarithms . As a consequence, naive Casimir scaling of the cusp anomalous dimensions associated with the quark and gluon form factors is violated, while a generalized form of Casimir scaling still holds. Our results provide an important ingredient for resummations of large logarithms in -jet cross sections with next-to-next-to-next-to leading logarithmic (NLL) accuracy.

31 pages, 3 figures. v2: journal version; note added with analytical result for k_1 from [73]; discussion of [42]

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