Two-Loop Spacelike Splitting Amplitudes in Full-Color QCD

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.