Probing the Symmetric Higgs Portal with Di-Higgs Boson Production

TL;DR

This paper assesses the potential to detect a scalar dark sector particle coupled via the Higgs portal through di-Higgs production at the LHC and future colliders, highlighting the importance of full momentum dependence in sensitivity estimates.

Contribution

It provides a detailed analysis of di-Higgs production sensitivity to Higgs portal couplings, including full momentum dependence, and compares it with other collider probes.

Findings

Di-Higgs production sensitivity is significantly affected by full momentum dependence.

Future colliders like FCC-hh can improve detection prospects for Higgs portal scalars.

Complementary probes include single Higgs measurements and missing energy searches.

Abstract

A coupling of a scalar, charged under an unbroken global U(1) symmetry, to the Standard Model via the Higgs portal is one of the simplest gateways to a dark sector. Yet, for masses $m_{S}\geq m_{H}/2$ there are few probes of such an interaction. In this note we evaluate the sensitivity to the Higgs portal coupling of di-Higgs boson production at the LHC as well as at a future high energy hadron collider, FCC-hh, taking into account the full momentum dependence of the process. This significantly impacts the sensitivity compared to estimates of changes in the Higgs-coupling based on the effective potential. We also compare our findings to precision single Higgs boson probes such as the cross section for vector boson associated Higgs production at a future lepton collider, e.g. FCC-ee, as well as searches for missing energy based signatures.