Precise Higgs-background predictions: merging NLO QCD and squared quark-loop corrections to four-lepton + 0,1 jet production

摘要

We present precise predictions for four-lepton plus jets production at the LHC obtained within the fully automated S herpa + O pen L oops framework. Off-shell intermediate vector bosons and related interferences are consistently included using the complex-mass scheme. Four-lepton plus 0- and 1-jet final states are described at NLO accuracy, and the precision of the simulation is further increased by squared quark-loop NNLO contributions in the gg → 4 ℓ , gg → 4 ℓ + g, g q → 4 ℓ + q , and $ q\overline{q} $ → 4 ℓ + g channels. These NLO and NNLO contributions are matched to the S herpa parton shower, and the 0- and 1-jet final states are consistently merged using the M eps @N lo technique. Thanks to Sudakov resummation, the parton shower provides improved predictions and uncertainty estimates for exclusive observables. This is important when jet vetoes or jet bins are used to separate four-lepton final states arising from Higgs decays, diboson production, and top-pair production. Detailed predictions are presented for the Atlas and C ms H → WW * analyses at 8 TeV in the 0- and 1-jet bins. Assessing renormalisation-, factorisation- and resummationscale uncertainties, which reflect also unknown subleading Sudakov logarithms in jet bins, we find that residual perturbative uncertainties are as small as a few percent.