Composite Higgs Boson Pair Production at the LHC

TL;DR

The paper investigates the feasibility of measuring the trilinear Higgs self-coupling $λ_{HHH}$ in composite Higgs models at the LHC, focusing on minimal models (MCHM4 and MCHM5) where the Higgs is a pseudo-Goldstone boson and $ξ=(v/f)^2$ controls deviations from the SM. It derives how $λ_{HHH}$ and other couplings are modified in terms of $ξ$ and Higgs mass $M_H$, and computes Higgs pair production cross sections across gluon fusion, vector-boson fusion, and Higgs-strahlung channels, including a new diagram in gluon fusion from the direct $HHqq$ coupling. By mapping sensitivity regions in the $(ξ, M_H)$ plane for final states like $b\bar b\gamma\gamma$, $b\bar b\tau\tau$, and $4W$ at realistic luminosities, the work identifies where deviations from the SM and nonzero $λ_{HHH}$ could be observed, highlighting the $4W$ channel as particularly promising for $M_H \gtrsim 120$ GeV. While backgrounds and detector effects are not exhaustively treated, the results offer valuable guidance for future, more detailed analyses aimed at reconstructing the Higgs potential and probing EWSB dynamics in composite Higgs scenarios.

Abstract

The measurement of the trilinear and quartic Higgs self-couplings is necessary for the reconstruction of the Higgs potential. This way the Higgs mechanism as the origin of electroweak symmetry breaking can be tested. The couplings are accessible in multi-Higgs production processes at the LHC. In this paper we investigate the prospects of measuring the trilinear Higgs coupling in composite Higgs models. In these models, the Higgs boson emerges as a pseudo-Goldstone boson of a strongly interacting sector, and the Higgs potential is generated by loops of the Standard Model (SM) gauge bosons and fermions. The Higgs self-couplings are modified compared to the SM and controlled by the compositeness parameter $ξ$ in addition to the Higgs boson mass. We construct areas of sensitivity to the trilinear Higgs coupling in the relevant parameter space for various final states.

Figures (11)

• Figure 1: Generic diagrams of the Higgs pair production processes at the LHC in the composite Higgs model: double Higgs-strahlung, $WW/ZZ$ fusion and $gg$ fusion.
• Figure 2: Higgs pair production processes as a function of the Higgs boson mass in the SM ($\xi=0$, upper left) and MCHM4 with $\xi = 0.2$ (upper right), 0.5 (bottom left) and 0.8 (bottom right). Arrows indicate the change in the cross section for a variation of $\lambda_{HHH}$ from 0.5 to 1.5 its value in the corresponding model.
• Figure 3: The same as in Fig.\ref{['fig:prodcxns4']}, but for MCHM5.
• Figure 4: The branching ratios in the SM and MCHM4 as a function of $M_H$.
• Figure 5: The branching ratios in MCHM5 as a function of $\xi$ for $M_H=120$ GeV (left) and $M_H=180$ GeV (right) Espinosa:2010vn.