A Bayesian view of the Higgs sector with higher dimensional operators

TL;DR

This work uses a Bayesian global fit to a dimension-6 Higgs EFT to quantify how New Physics at ~3 TeV can modify Higgs couplings while remaining consistent with LHC/Tevatron data and electroweak constraints. By separating tree- and loop-induced effects and incorporating tensorial weak-boson couplings, the analysis finds substantial freedom in Higgs-top and total width deviations, modest shifts in vector boson couplings, and potentially large enhancements in $h o Zγ$, with $R_{ ext{width}}$ limited to roughly $0.7$–$2.7$ and $R_{γγ}$ mildly enhanced. The study explores two NP scenarios (democratic HDOs and loop-suppressed $ ext{O}_{FF}$s) using MCMC with priors that ensure EFT convergence, reporting correlations among EFT coefficients and their impact on observables like $R_{ggF}$, $R_{VBF}$, and $R_{Zγ}$. The results underscore the sensitivity of tensorial operators to loop-induced Higgs channels and emphasize the role of future $Zγ$ measurements at the LHC Run 2/3 in constraining the Higgs EFT parameter space and guiding NP model building.

Abstract

We investigate the possibilities of New Physics affecting the Standard Model (SM) Higgs sector. An effective Lagrangian with dimension-six operators is used to capture the effect of New Physics. We carry out a global Bayesian inference analysis, considering the recent LHC data set including all available correlations, as well as results from Tevatron. Trilinear gauge boson couplings and electroweak precision observables are also taken into account. The case of weak bosons tensorial couplings is closely examined and NLO QCD corrections are taken into account in the deviations we predict. We consider two scenarios, one where the coefficients of all the dimension-six operators are essentially unconstrained, and one where a certain subset is loop suppressed. In both scenarios, we find that large deviations from some of the SM Higgs couplings can still be present, assuming New Physics arising at 3 TeV. In particular, we find that a significantly reduced coupling of the Higgs to the top quark is possible and slightly favored by searches on Higgs production in association with top quark pairs. The total width of the Higgs boson is only weakly constrained and can vary between 0.7 and 2.7 times the Standard Model value within 95% Bayesian credible interval (BCI). We also observe sizeable effects induced by New Physics contributions to tensorial couplings. In particular, the Higgs boson decay width into $Zγ$ can be enhanced by up to a factor 12 within 95% BCI.

Figures (10)

• Figure 1: Posterior PDFs of the 9 fundamental parameters, $\beta_i \equiv \alpha_i v^2/\Lambda^2$, in scenario I (black) and scenario II (red).
• Figure 2: Posterior PDFs of $\beta_{W\space B}$ versus $\beta_{D}$ in scenario I (left) and scenario II (right). The red and blue regions correspond to the 68% and 95% Bayesian credible regions (BCRs). The green star indicates the maximum of our posterior PDF.
• Figure 3: On the left, posterior PDF of $c_t$ in scenario I (black) and scenario II (red). On the right, profile likelihood along the $c_t$ axis in scenario I and scenario II (same color code).
• Figure 4: Posterior PDF of $\beta_{GG}$ versus $\beta_t$ in scenario I (left) and scenario II (right). Color code as in Fig. \ref{['fig:corr_D_WB']}.
• Figure 5: On the left, posterior PDF of $R_{\gamma\gamma}$ in scenario I (black) and scenario II (red). Also shown are the 2D posterior PDFs of $R_{\rm width}$ versus $R_{\gamma\gamma}$ (middle) and $R_{\rm ggF}$ versus $R_{\gamma\gamma}$ (right) in scenario I. Color code as in the previous figure.