Abstract
We present a calculation of the next-to-leading order (NLO) QCD corrections to gluon-induced electroweak gauge boson pair production, gg rightarrow ZZ and gg rightarrow W^+W^-, matched to the PYTHIA 8 parton shower in the POWHEG approach. The calculation consistently incorporates the continuum background, the Higgs-mediated ggrightarrow H^* rightarrow VV process, and their interference. We consider leptonic decay modes of the vector bosons and retain offshell and non-resonant contributions. The processes considered are loop-induced at leading order and thus contain two-loop virtual contributions as well as loop-squared real contributions. Parton-shower effects are found to be marginal in inclusive observables and quite sizeable in observables that are exclusive in additional jet radiation. The Monte Carlo generator presented here allows for realistic experimental effects to be incorporated in state-of-the-art precision analyses of diboson production and of the Higgs boson in the offshell regime.
Highlights
In this paper, we will focus on the production of an offshell Higgs boson through gluon fusion and its subsequent decay into a pair of electroweak gauge bosons
At next-to-leading order (NLO), the two-loop gg → V V amplitudes for massless quarks circulating in the loop have been known for several years [26,27], and allow for offshell vector bosons
We report on NLO calculations for offshell Higgs production, including interference effects, matched to parton showers using the POWHEG method [49,50,51,52]
Summary
We will focus on the production of an offshell Higgs boson through gluon fusion and its subsequent decay into a pair of electroweak gauge bosons. Offshell amplitudes are required for a consistent NLO description in the entire phase-space, the onshell treatment of the vector bosons is not a serious deficiency for offshell Higgs studies This means that a fully consistent NLO prediction with the exact dependence on the top-quark mass is in sight in this kinematic regime but still not available. Reliable NLO corrections to the continuum background gg → V V alone can be obtained ignoring heavy quark contributions (or these can be incorporated via a reweighting of the massless two-loop amplitude with the LO mass dependence) They are available in the literature both for gg → Z Z [37,38] and gg → W +W − [39,40].1.
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