Real Singlet Scalar Benchmarks in the Multi-TeV Resonance Regime

TL;DR

This paper investigates the potential for resonant di-Higgs production and modifications to the Higgs trilinear coupling in a Standard Model extension with a real scalar singlet, focusing on current and future collider scenarios.

Contribution

It provides updated and extended benchmark analyses for multi-TeV scalar resonances affecting di-Higgs production and Higgs self-coupling at various collider configurations.

Findings

Resonant di-Higgs rate can be an order of magnitude larger than SM predictions.

Higgs trilinear coupling can be up to three times larger than SM in certain mass ranges.

Enhanced effects are near the projected sensitivity limits of future colliders.

Abstract

Scalar extensions of the Standard Model are of much interest at the LHC and future colliders. In particular, these models can give rise to resonant di-Higgs production and alter the Higgs trilinear coupling. In this paper, we study di-Higgs production in the Standard Model extended by a real scalar singlet with no additional symmetries. We determine how large the resonant di-Higgs rate and variation in the Higgs trilinear coupling can be in four scenarios: current LHC results and projected results at the HL-LHC, the HL-LHC combined with a circular $e^-e^+$ collider such as the CEPC or FCC-ee, and the HL-LHC combined with a linear $e^-e^+$ collider such as the ILC. While these are updated results from a previous study using current LHC data, we go further and find benchmark points in the multi-TeV resonance regime for future colliders beyond the HL-LHC. Considering current LHC results, the resonant di-Higgs rate can still be an order of magnitude larger than the SM predicted di-Higgs rate. In the HL-LHC scenario, the Higgs trilinear coupling can still be a factor of three larger than the SM prediction for resonance masses in the $1.5-3.5$ TeV range, where resonant searches may have less reach. This enhancement is just at the projected 2$\sigma$ sensitivity of the HL-LHC. We find there are resonance masses for which the change in the Higgs trilinear is maximized while the resonant rate is negligible. We provide an analytical understanding of these effects with a discussion on the interplay of various constraints on the parameter space and the Higgs trilinear coupling.