Two-Loop Spacelike Splitting Amplitudes in Full-Color QCD

TL;DR

This paper presents the first complete two-loop spacelike splitting amplitudes in full-color QCD across all channels, confirming universality and revealing new collinear factorization-violating effects.

Contribution

It provides the first comprehensive results for two-loop spacelike splitting amplitudes in full-color QCD, including all channels and helicities, and explores factorization properties.

Findings

Confirmed universality of certain contributions from N=4 super Yang--Mills theory.

Identified new sources of collinear factorization-violating effects.

Showed CFV effects cancel in color-summed squared amplitudes, supporting universality.

Abstract

The study of QCD scattering amplitudes in the collinear regime provides crucial insight into the factorization properties of hadronic cross sections. In this paper, we present the first complete results for two-loop spacelike splitting amplitudes in full-color QCD, in all partonic channels and helicity configurations. We confirm the universality of a class of contributions already found in N=4 super Yang--Mills (sYM) theory, and identify previously unknown sources of collinear factorization-violating (CFV) effects. Consistent with recent observations in N=4 sYM, all CFV contributions cancel in color-summed squared amplitudes, implying the universality of single-parton collinear factorization for jet cross sections at third order in QCD.