Probing the Higgs self coupling via single Higgs production at the LHC

TL;DR

This work tackles the problem of measuring the Higgs trilinear self-coupling $\lambda_{3}$ beyond direct Higgs-pair production. It proposes a method leveraging electroweak loop corrections to single-Higgs production and decay, parameterized by $\kappa_{\lambda}$, and computes the corresponding $C_{1}$ and universal $C_{2}$ coefficients across 주요 channels. By performing a one-parameter fit to LHC8 data and projecting Run II/HL-LHC sensitivities, the authors show that bounds on $\kappa_{\lambda}$ can be competitive with those from double-Higgs production, with the potential to tighten further using differential information and future data. The analysis relies on the assumption that new physics primarily affects the Higgs potential and its trilinear coupling, leaving most tree-level Higgs couplings near their SM values, and discusses extensions to EFT frameworks. Overall, the method offers a complementary and potentially more accessible avenue to probe the Higgs self-coupling and the Higgs sector’s structure at the LHC.

Abstract

We propose a method to determine the trilinear Higgs self coupling that is alternative to the direct measurement of Higgs pair production total cross sections and differential distributions. The method relies on the effects that electroweak loops featuring an anomalous trilinear coupling would imprint on single Higgs production at the LHC. We first calculate these contributions to all the phenomenologically relevant Higgs production ($gg{\rm F}$, VBF, $WH$, $ZH$, $t\bar tH$) and decay ($γγ$, $WW^{*}/ZZ^{*}\to 4f$, $b\bar b$, $ττ$) modes at the LHC and then estimate the sensitivity to the trilinear coupling via a one-parameter fit to the single Higgs measurements at the LHC 8 TeV. We find that the bounds on the self coupling are already competitive with those from Higgs pair production and will be further improved in the current and next LHC runs.

Figures (13)

• Figure 1: One-loop $\lambda_{3}$-dependent diagram in the Higgs self-energy.
• Figure 2: Structure of the $\lambda_{3}^{\rm SM}$-dependent part in $\mathcal{M}^1_{\lambda_{3}^{\rm SM}}$ for processes involving massive vector bosons in the final or in the intermediate states (VBF, $HV$ and $H\rightarrow V V^* \rightarrow 4f$).
• Figure 3: Sample of $\lambda_{3}^{\rm SM}$-dependent diagrams in $t\bar{t}H$ production.
• Figure 4: Diagrams contributing to the $C_1$ coefficient in the gluon-gluon-fusion Higgs production. The one on the right has a multiplicity factor 2.
• Figure 5: Diagrams contributing to the $C_1$ coefficient in $\Gamma ( H \to \gamma \gamma)$. The diagrams in the second row have multiplicity 2.