NNLO QCD predictions for $Wγγ$ production at the LHC

Abstract

Triboson production processes play a crucial role in probing the electroweak sector of the Standard Model, as they involve quartic gauge-boson couplings already at the tree level. With these measurements entering the precision era at the Large Hadron Collider (LHC), accurate theoretical predictions become indispensable. We present the computation of the next-to-next-to-leading-order (NNLO) QCD radiative corrections to the production of a $W$ boson in association with two photons ($Wγγ$) at the LHC. The calculation is exact, except for the finite part of the two-loop contribution, which is included in the leading-colour approximation. Predictions for the fiducial cross section and selected kinematic distributions are provided at a centre-of-mass energy of $\sqrt{s}=13$ TeV, under standard experimental selection cuts. In line with observations for other multiboson processes involving direct photons, we find sizable NNLO corrections that enhance the next-to-leading-order predictions by about $23\%$, with residual perturbative uncertainties that can be roughly estimated to be at the $5\%$ level.

Figures (2)

• Figure 1: $r_{\mathrm{cut}}$ dependence of the NLO and NNLO cross sections for $pp\rightarrow \ell^-\bar{\nu}_\ell\gamma\gamma$ (dotted points with errorbars) and the extrapolated result, $r_{\mathrm{cut}}\xspace\rightarrow 0$ (solid), at the central scale $\mu_F\xspace=\mu_R\xspace$.
• Figure 2: Distributions in the transverse momentum of the leading photon, $p_{T,\gamma_1}$ (left), and in the difference in rapidities between the charged lepton and the diphoton system, $\Delta y_{\ell,\gamma\gamma}$ (right), are presented for $W\gamma\gamma$ production. The upper panels show the absolute prediction at LO, NLO and NNLO accuracy, the lower panels relative corrections normalised by the NLO prediction, together with their conventional (symmetrised) seven-point scale-variation bands.