Complete Higgs Sector Constraints on Dimension-6 Operators

TL;DR

This paper constrains the full set of CP-even dimension-6 Higgs operators within the SMEFT by combining Higgs signal strengths with differential information from VH production. It demonstrates that differential distributions in $VH$ production, specifically $m_{VH}$ and $p_T^V$, provide stronger sensitivity and help resolve degeneracies inherent in LEP-era TGC measurements. A global fit incorporating these distributions shows significantly tightened 95% CL bounds on the operator coefficients and clarifies how VH data complement EWPT and TGC constraints. The work underscores the value of high-energy VH kinematics for precision Higgs EFT analyses and points to stronger future limits with LHC Run 2+ data.

Abstract

Constraints on the full set of Standard Model dimension-6 operators have previously used triple-gauge couplings to complement the constraints obtainable from Higgs signal strengths. Here we extend previous analyses of the Higgs sector constraints by including information from the associated production of Higgs and massive vector bosons (H+V production), which excludes a direction of limited sensitivity allowed by partial cancellations in the triple-gauge sector measured at LEP. Kinematic distributions in H+V production provide improved sensitivity to dimension-6 operators, as we illustrate here with simulations of the invariant mass and $p_T$ distributions measured by D0 and ATLAS, respectively. We provide bounds from a global fit to a complete set of CP-conserving operators affecting Higgs physics.

Figures (8)

• Figure 1: Simulation of the $m_{VH}$ distribution in $(V \to 2 \ell) + (H \to {\bar{b}}b)$ events at the Tevatron after implementing D0 cuts, obtained using MadGraph v2.1.0 interfaced with Pythia and Delphes v3, combined with the dimension-6 model implementation developed in benj. The solid distribution is the SM expectation, while the red-dotted and blue-dashed lines correspond to the distributions with $\bar{c}_W$ =0.1 and 0.035, respectively.
• Figure 2: The one-dimensional fit to the parameter $\bar{c}_W$ (left panel) and to $\bar{c}_{HW}$ (right panel). In each panel, the dashed-red line corresponds to the constraint from the 0-, 1- and 2-lepton D0 $m_{VH}$ distribution including all bins, the dashed-blue line to the 0-, 1- and 2-lepton ATLAS $p_T^V$ distribution using the last bin only, the dashed-black is the combination of CMS and ATLAS signal strengths in all channels except $VH$, and the solid-black is the combination of all the above.
• Figure 3: The invariant mass (left panel) and transverse momentum (right panel) distributions for LHC Run 1 at 8 TeV, calculated with LO and NLO QCD and compared with the effects of an effective operator.
• Figure 4: Simulation of the $p_T^V$ distribution in $(V \to 2 \ell) + (H \to {\bar{b}}b)$ events at the LHC after implementing ATLAS cuts, as obtained using MadGraph v2.1.0 interfaced with Pythia and Delphes v3, combined with the dimension-6 model implementation developed in benj. The solid distribution is the SM expectation, and the red-dotted and blue-dashed lines correspond to the distributions with $\bar{c}_W$ =0.1 and 0.05, respectively.
• Figure 5: Regions in the $({\bar{c}}_{W}, {\bar{c}}_{HW})$ planes allowed at the 68 (95) (99)% CL (in lighter shading and bounded by dotted, dashed and solid lines, respectively) in fits to the D0 $m_{VH}$ data alone (upper left panel), the ATLAS $p_T^V$ data alone (upper right panel), the combination of these data (lower left panel) and a global fit using also signal-strength information from CMS and ATLAS (lower right panel).