Multiple soft radiation at one-loop order and the emission of a soft quark–antiquark pair

Abstract We consider the radiation of two or more soft partons in QCD hard-scattering at one-loop order. The corresponding scattering amplitude is singular, and singular behaviour controlled by a process-independent current. Using regularization $$d=4 - 2\epsilon $$ d = 4 - 2 ϵ space-time dimensions, we explicitly evaluate ultraviolet infrared divergent ( $$\epsilon -pole) terms current for emission an arbitrary number generic process. Then specific case quark–antiquark $$q{{\bar{q}}}$$ q ¯ ) compute including finite terms. find that soft- exhibits new type transverse-momentum singularity, which has quantum (absorptive) origin purely non-abelian character. At squared (cross section) level, this singularity produces contributions to multijet production processes hadron collisions. also leads charge asymmetry terms, are distinctive features radiation. extend these results cases QED mixed $$\times × radiative corrections fermion–antifermion emission.