Vector boson pair production at hadron colliders

Abstract

We calculate the contribution of gluon-gluon induced processes to vector boson pair production at hadron colliders, specifically the production of WZ, Wγ and Zγ pairs. We calculate the tree level processes gg → WZqq, gg → Wγqq and gg → Zγqq, and the one loop process gg → Zγ. We use the helicity method and include the decay of the W and Z bosons into leptons in the narrow width approximation. We include anomalous triple gauge couplings in all of our vector boson pair production calculations. In order to integrate over the qq final state phase space we use an extended version of the subtraction method to NNLO and cancel collinear singularities ex-plicitly. The general subtraction terms that are obtained apply to all vector boson pair production processes. Due to the large gluon density at low z, the gluon induced terms of vector boson pair production are expected to be the dominant NNLO QCD correction, relevant at LHC energies. However, we show that due to a cancellation they turn out to provide a rather small contribution, anticipating good stability for the perturbative expansion. This contribution remains small even when anomalous couplings are added, and when one considers energies far above the energies of currently planned hadron colliders.