Quark–gluon antenna functions from neutralino decay

The computation of exclusive QCD jet observables at higher orders requires a method for the subtraction of infrared singular configurations arising from multiple radiation of real partons. One commonly used method at next-to-leading order (NLO) is based on the antenna factorization of colour-ordered matrix elements, and uses antenna functions to subtract the real radiation singularities. Up to now, NLO antenna functions could be derived in a systematic manner only for hard quark–antiquark pairs, while the gluon–gluon and quark–gluon antenna functions were constructed from their limiting behaviour. In this Letter, we show that antenna functions for hard quark–gluon pairs can be systematically derived from an effective Lagrangian describing heavy neutralino decay. The infrared structure of the colour-ordered neutralino decay matrix elements at NLO and NNLO is shown to agree with the structure observed for parton radiation off a quark–gluon antenna.