Gluon induced contributions toWZandWγproduction at NNLO

Abstract

Additional information: Use policyThe full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-prot purposes provided that:• a full bibliographic reference is made to the original source • a link is made to the metadata record in DRO • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders.Please consult the full DRO policy for further details. AbstractWe calculate the contribution of the partonic processes gg → W Zqq and gg → W γqq to W Z and W γ pair production at hadron colliders, including anomalous triple gauge-boson couplings. We use the helicity method and include the decay of the W and Z-boson into leptons in the narrow-width approximation. In order to integrate over the qq final state phase space we use an extended version of the subtraction method to NNLO and remove collinear singularities explicitly. Due to the large gluon density at low x, 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.

Gluon induced contributions toZγproduction at hadron colliders

“…For the numerical results presented in this section we follow closely the analysis presented in [9]. We use the MRST 2001 parton distribution functions [23] with the one-loop expression for the coupling constant (α s (M Z ) = 0.119).…”

Isolating a light Higgs boson from the diphoton background at the CERN LHC

“…Therefore, it is reasonable to consider the gg → γγX contributions as a first approximation to the full NNLO calculation. A study of the similar subprocesses, gg → W V qq ′ where V = γ or Z, was recently carried out, with the conclusion that their effects are actually quite small, 5% or less (and negative), with respect to the lower-order contributions of the qq and qg initial states [27]. Assuming that these results also hold for the γγ final state, our neglect of gg → γγqq should be tolerable.…”

The two-loop helicity amplitudes for gg → V 1 V 2 → 4 leptons

“…This implies that it formally contributes only at NNLO in the perturbative expansion of the hadronic process, but numerical enhancements may be expected due to the large gluon luminosities at typical energies for diboson production at the LHC. For the gluon-induced processes, the oneloop amplitudes and the corresponding one-loop squared interference terms have been computed long ago [6][7][8][9][10][11][12]. Their impact on the total cross section was found to range approximately from 5% to more than 10% for different final states at the LHC, and to rise with increasing collider energy [1][2][3][4].…”