Next-to-leading order QCD corrections to W+W- production via vector-boson fusion

TL;DR

The paper computes next-to-leading order QCD corrections to W+W- production via vector-boson fusion in proton-proton collisions, including full leptonic decays and all resonant/non-resonant diagrams within the VBF-dominated region. A fully flexible parton-level Monte Carlo is developed to evaluate cross sections with realistic VBF cuts, combining real and virtual corrections using dimensional reduction and Passarino-Veltman reduction, with careful treatment of pentagon-loop diagrams and gauge invariance. The findings show modest NLO corrections (<10% on total cross sections) and high perturbative stability (sub-2% scale uncertainty), though some differential distributions exhibit shape changes (K-factors between ~0.8 and 1.2). These results establish EW W+W-jj production as a reliably predictable background to Higgs and EW phenomena, and the modular framework supports future extensions to new physics in the electroweak sector.

Abstract

Vector-boson fusion processes constitute an important class of reactions at hadron colliders, both for signals and backgrounds of new physics in the electroweak interactions. We consider what is commonly referred to as W+W- production via vector-boson fusion (with subsequent leptonic decay of the Ws), or, more precisely, e+ nu_e mu- nubar_mu + 2 jets production in proton-proton scattering, with all resonant and non-resonant Feynman diagrams and spin correlations of the final-state leptons included, in the phase-space regions which are dominated by t-channel electroweak-boson exchange. We compute the next-to-leading order QCD corrections to this process, at order alpha^6 alpha_s. The QCD corrections are modest, changing total cross sections by less than 10%. Remaining scale uncertainties are below 2%. A fully-flexible next-to-leading order partonic Monte Carlo program allows to demonstrate these features for cross sections within typical vector-boson-fusion acceptance cuts. Modest corrections are also found for distributions.

Figures (14)

• Figure 1: The six Feynman-graph topologies contributing to the Born process $uc\,\hbox{$\rightarrow$}\, uc\,e^+\nu_e \,\mu^-\bar{\nu}_\mu$, a template for neutral-current processes. Diagrams analogous to (a), (b), (e) and (f), with vector-boson emission off the lower quark line, are not shown.
• Figure 2: Diagrams contributing to the scattering amplitude $T_{W^+V}^{\alpha\beta}$, depicted in Fig. \ref{['fig:feynBorn']} (e), that describe the tree-level subprocess $W^+V\hbox{$\rightarrow$} e^+\nu_e$, where $V$ is a $\gamma$ or a $Z$ vector boson, and $\alpha$ and $\beta$ are the tensor indices carried by the charged and neutral vector bosons, respectively.
• Figure 3: Contribution from $W^+W^-$ fusion to the scattering process $us\,\hbox{$\rightarrow$}\, dc\, e^+\nu_e \,\mu^-\bar{\nu}_\mu$. The tensor $T_{W^+W^-}^{\alpha\beta}$ contains all the tree-level diagrams contributing to the process $W^+W^-\,\hbox{$\rightarrow$}\,e^+\nu_e \,\mu^-\bar{\nu}_\mu$, where $\alpha$ and $\beta$ are the tensor indices carried by the $W^+$ and $W^-$ vector bosons, respectively.
• Figure 4: Virtual corrections for a fermion line with two attached vector bosons, $V_1(q_1)$ and $V_2(q_2)$. The finite part of the sum of these graphs defines the reduced amplitude $\widetilde{\cal M}_{V_1 V_2,\tau}$q_1,q_2$$ of Eq. (\ref{['eq:boxlinefig']}).
• Figure 5: Virtual corrections for a fermion line with three attached vector bosons, $V_1(q_1)$, $V_2(q_2)$ and $V_3(q_3)$. The finite part of the sum of these graphs defines the reduced amplitude $\widetilde{\cal M}_{V_1 V_2 V_3,\tau}$q_1,q_2,q_3$$ of Eq. (\ref{['eq:pentalinefig']}).