Is the Standard Model Effective Field Theory Enough for Higgs Pair Production?

Abstract

We study Higgs-boson pair production in the Standard Model Effective Field Theory (SMEFT) up to dimension six and in the Higgs Effective Field Theory (HEFT) at leading order in the effective theory expansion, and assess which description is appropriate in concrete UV scenarios. Motivated by "Loryon"-inspired models, we compare the Higgs pair production cross sections predicted by the full models to their SMEFT and HEFT counterparts. We identify regimes in which the two EFTs provide comparable descriptions, and clarify the limits required for their couplings to match. We also find that, for parts of parameter space in some of these models, HEFT can reproduce Higgs pair production more accurately than SMEFT, highlighting di-Higgs measurements as a potential probe of non-linear electroweak dynamics.

Figures (7)

• Figure 1: Ratio of the SMEFT and HEFT predictions for the coupling modifiers $c_{hVV}$ and $c_{hhVV}$ for a scan over the parameter space, using $\lambda_2\in [0,4\pi]$, $\lambda_3\in [-4\pi, 4 \pi]$, $|\sin \theta| < 0.15$, $v_S\in [0.01, 5 v_H]$ and $M\in [2,3]\text{ TeV}$ (blue points). For the red points instead the range of $v_S$ was constrained to lie within $v_S\in [0.01, 0.1v_H]$.
• Figure 2: Cross section for Higgs production in gluon fusion using the scalar singlet model. On the right (left) panel we display ratio of $\sigma_{\text{UV}}$ over the same quantity computed in HEFT (SMEFT) framework. Red (blue) points refer to scan 1 (scan 2) which allows for small values only (also order one values) of $v_S/v_H$.
• Figure 3: Unpolarized amplitudes squared for Higgs pair production in vector boson fusion for the scalar singlet model. On the right (left) panel we display the ratio of the unpolarized amplitude squared in the UV model over the same quantity computed in HEFT (SMEFT) framework .
• Figure 4: Ratio of the full model cross section over the EFT cross section, for the 2HDM of type I (left) and type II (right). The black points show the case of matching to the HEFT and the orange points show the case of matching to the SMEFT.
• Figure 5: Ratio of the full model cross section over the EFT cross section, for the 2HDM of type I truncating the SMEFT at $\mathcal{O}(1/\Lambda^2)$ at the matrix element level, while keeping quadratic terms in the cross section.