Higgs characterisation via vector-boson fusion and associated production: NLO and parton-shower effects

TL;DR

This work develops and applies an EFT-based Higgs characterisation framework to vector-boson fusion and associated production at the LHC, focusing on spin-0 hypotheses and dimension-6 operators. By implementing the HC EFT in FeynRules and generating NLO QCD predictions matched to parton showers via MadGraph5_aMC@NLO, the authors demonstrate that NLO corrections are essential for both total-rate uncertainties and the accurate shaping of kinematic distributions, across VBF and VH channels. The study covers six benchmark scenarios, including CP-even, CP-odd, derivative, and CP-mixed cases, and shows that NLO+PS effects are observable in observables like $m_{jj}$, $p_T^X$, and angular variables, with certain operators influencing high-$p_T$ tails and jet kinematics. Overall, the paper provides a fully automatic, EFT-based, NLO+PS framework that enhances Higgs characterisation efforts at the LHC and supports precise constraints on possible new physics in Higgs interactions, ready for use in experimental analyses.

Abstract

Vector-boson fusion and associated production at the LHC can provide key information on the strength and structure of the Higgs couplings to the Standard Model particles. Using an effective field theory approach, we study the effects of next-to-leading order (NLO) QCD corrections matched to parton shower on selected observables for various spin-0 hypotheses. We find that inclusion of NLO corrections is needed to reduce the theoretical uncertainties on total rates as well as to reliably predict the shapes of the distributions. Our results are obtained in a fully automatic way via FeynRules and MadGraph5_aMC@NLO.

Figures (5)

• Figure 1: Distribution for the invariant mass of the two leading jets in VBF production with the acceptance cuts. The histograms in the main plot are normalized to unity.
• Figure 2: Distributions for $p_T^X$, $\eta^X$, $p_T^{j_1}$, $\eta^{j_1}$, $\Delta\eta(j_1,j_2)$, and $\Delta\phi(j_1,j_2)$ in VBF with the acceptance cuts for the jets. The histograms in the main plots are normalized to unity.
• Figure 3: Same as fig. \ref{['fig:vbf1']}, but with the additional VBF cut in eq. \ref{['mjjcut']}.
• Figure 4: Distributions for $p_T^X$, $\eta^X$, and $p_T^{\ell}$ in $W^+H$ (left) and in $ZH$ (right) production with the acceptance cuts for the lepton(s). The histograms in the main plots are normalized to unity.
• Figure 5: Distributions for $\cos\theta^*$ and $\cos\theta_{\ell}$ in $ZH$ with the acceptance cuts for the leptons. The histograms in the main plots are normalized to unity.