The triple collinear limit of one-loop QCD amplitudes

Abstract

We consider the singular behaviour of one-loop QCD matrix elements when several external partons become simultaneously parallel. We present a new factorization formula that describes the singular collinear behaviour directly in colour space. The collinear singularities are embodied in process-independent splitting matrices that depend on the momenta, flavours, spins and colours of the collinear partons. We give the general structure of the infrared and ultraviolet divergences of the one-loop splitting matrices. We also present explicit one-loop results for the triple collinear splitting, $q\to q\bar{Q}Q$, of a quark and a quark--antiquark pair of different flavours. The one-loop triple collinear splitting is one of the ingredients that can be used to compute the evolution of parton distributions at the next-to-next-to-leading order in QCD perturbation theory.

11 pages, 1 figure, uses axodraw. Final version to appear in Phys.Lett.B. One reference added

References in corpus (4)

• Multi-Parton Amplitudes in Gauge Theories
• Soft-gluon resummation for Higgs boson production at hadron colliders
• Planar Amplitudes in Maximally Supersymmetric Yang-Mills Theory
• Evolution Kernels from Splitting Amplitudes

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