WW production at high transverse momenta beyond NLO

TL;DR

This study presents an approximate NNLO prediction for WW production at the LHC by merging NLO results for WW and WW+jet with LoopSim, including loop-squared gluon-fusion contributions. It demonstrates that higher-order QCD corrections beyond NLO are sizable for radiation-sensitive observables and that jet vetoes induce large negative Sudakov logarithms, significantly reducing cross sections in high-energy regions. The findings indicate that LoopSim captures the dominant NNLO effects for many distributions, though full NNLO constant terms remain unaccounted for, underscoring the need for complete NNLO calculations. The work also provides practical, publicly usable tools to improve WW background modeling in Higgs and new-physics analyses.

Abstract

Pair production of W gauge bosons is an important process at the LHC entering many experimental analyses, both as background in new-physics searches or Higgs measurements and as signal in precision studies and tests of the Standard Model. Therefore, accurate predictions for this class of processes are of great interest in order to exploit the full potential of LHC measurements. We use the LoopSim method to combine NLO QCD results for WW and WW+jet, as well as the loop-squared gluon-fusion contribution, to obtain approximate NNLO predictions for WW production. The cross sections are calculated with VBFNLO and include leptonic decays of the W bosons as well as finite-width and off-shell effects. We find that the size of the additional corrections beyond NLO can be significant and well outside of the NLO error bands given by renormalization and factorization scale variation. Applying a jet veto, we observe further negative corrections at NNLO, which we relate to the presence of large Sudakov logarithms.

Figures (5)

• Figure 1: Differential cross sections and K-factors for the effective mass observable, defined in Eq. (\ref{['eq:HT']}), for the LHC at $\sqrt{s}=8\, \text{TeV}$. The bands correspond to varying $\mu_F=\mu_R\equiv \mu$ by factors 1/2 and 2 around the central value from Eq. (\ref{['eq:ren']}). The cyan solid bands give the uncertainty related to the $R_\text{LS}$ parameter varied between 0.5 and 1.5. The distribution is a sum of contributions from $e^+ \nu_e e^- \bar{\nu}_e$, $\mu^+\nu_\mu \mu^-\bar{\nu}_\mu$, $e^+ \nu_e \mu^-\bar{\nu}_\mu$ and $\mu^+\nu_\mu e^- \bar{\nu}_e$ decay channels. The contribution from the gluon-fusion box and Higgs diagrams is included in the NLO and $\bar{n}$ NLO curves. The left panels correspond to the inclusive sample, while the results shown in the right panel were obtained with vetoing events containing jets which fulfill the criteria $p_{T,\,\mathrm{jet}\xspace} > 30 \,\mathrm{GeV}\xspace$ and $|\eta_{\,\mathrm{jet}\xspace}| < 4.7$.
• Figure 2: Differential cross sections and K-factors for the $p_T$ of the hardest lepton for the LHC at $\sqrt{s}=8\, \text{TeV}$ without (left) and with jet veto (right). Details are as in Fig. \ref{['fig:HT']}.
• Figure 3: Differential cross sections and K-factors for the missing transverse energy for the LHC at $\sqrt{s}=8\, \text{TeV}$ without (left) and with jet veto (right). Details are as in Fig. \ref{['fig:HT']}.
• Figure 4: Differential cross sections and K-factors for the invariant mass of the dilepton system for the LHC at $\sqrt{s}=8\, \text{TeV}$ without (left) and with jet veto (right). Details are as in Fig. \ref{['fig:HT']}.
• Figure 5: Differential cross sections and K-factors for the invariant mass of the diboson system for the LHC at $\sqrt{s}=8\, \text{TeV}$ without (left) and with jet veto (right). Details are as in Fig. \ref{['fig:HT']}.