Heavy-quark mass effects in Higgs plus jets production

TL;DR

This study assesses Higgs production in gluon fusion at the LHC with up to two associated jets, explicitly including top and bottom quark mass effects and comparing results to EFT approximations. It combines NLO QCD predictions with FxFx merging and parton-shower matching, using MadGraph5_aMC@NLO and Pythia8, and treats heavy-quark contributions in a mass-aware way while maintaining computational efficiency via reweighting and selective exact amplitudes. The main finding is that both multi-jet merging and heavy-quark masses significantly affect inclusive rates and a wide range of differential observables, particularly at higher Higgs pT and in jet-rich final states; bottom loops mainly influence low-multiplicity regions, while top-mass effects emerge prominently at high pT. The results underline the need to include these effects for realistic, collider-level predictions and provide guidance for experimental analyses aiming to probe Higgs production dynamics and potential beyond-Standard-Model contributions.

Abstract

We study the production of a Standard Model Higgs boson in the gluon-fusion channel at the 13 TeV LHC. Our results are accurate to the next-to-leading order in QCD, bar for the lack of some two-loop amplitudes, for up to two extra jets and are matched to the PYTHIA8 Monte Carlo. We address the impact, at the level of inclusive rates and of differential distributions, of the merging of samples characterised by different final-state multiplicities, and of the effects induced by top and bottom masses through heavy-quark loop diagrams. We find that both the merging and the heavy-quark masses must be included in the calculation in order to realistically predict observables of experimental interest.

Figures (7)

• Figure 1: Inclusive Higgs transverse momentum. The main frame displays the central results for our standard four predictions, as well as the hard-scale uncertainty band relevant to ${\rm FxFx}_{\rm M}$. The upper inset presents ratios of the central results over the ${\rm FxFx}_{\rm M}$ one. The middle insets highlights heavy-quark mass effects in both merged and inclusive predictions. The lower insets shows fractional hard- and merging-scale uncertainties for ${\rm FxFx}_{\rm M}$. See the text for further details.
• Figure 2: Higgs transverse momentum with $N_{jet}=0$, $N_{jet}=1$, and $N_{jet}\ge 2$. The main frame displays the central ${\rm FxFx}_{\rm M}$ predictions and their hard-scale uncertainty bands. Each inset is relevant to one $N_{jet}$ multiplicity, and presents ratios computed with the central ${\rm FxFx}_{\rm M}$ result as denominator. We show the merged EFT and both inclusive predictions, and the fractional hard- and merging-scale uncertainty of ${\rm FxFx}_{\rm M}$. See the text for further details.
• Figure 3: Same as in fig. \ref{['fig:Higgsptjetbin']}, for the transverse momenta of the four hardest jets.
• Figure 4: Same as in fig. \ref{['fig:Higgsptinc']}, for the azimuthal distance between the two hardest jets.
• Figure 5: Same as in fig. \ref{['fig:Higgsptinc']}, for the invariant mass of the pair of the two hardest jets.