Higgs-boson visible and invisible constraints on hidden sectors

TL;DR

This paper analyzes how measurements of the Higgs boson constrain hidden sectors and invisible decay channels, showing that indirect constraints often surpass direct searches in limiting new physics scenarios.

Contribution

It provides a comprehensive analysis of Higgs measurements to set limits on hidden sector interactions and invisible decays, applying these to various models including dark matter and extended Higgs sectors.

Findings

Indirect constraints are stronger than direct search limits in many models.

Invisible Higgs decay modes can open parameter space regions otherwise excluded.

Fermionic dark matter in simple Higgs-portal models is ruled out by new experimental data.

Abstract

We investigate the impact of interactions between hidden sectors and the discovered Higgs boson $h_{125}$, allowing for additional invisible decay channels of $h_{125}$. We perform $\chi^2$-fits to the measurements of the Higgs-boson cross sections as a function of the invisible branching ratio and different combinations of coupling modifiers, where the latter quantify modifications of the couplings of $h_{125}$ compared to the predictions of the Standard Model. We present generic results in terms of exclusion limits on the coupling modifiers and the invisible branching ratio of $h_{125}$. Additionally, we apply our results to a variety of concrete model realizations containing a hidden sector: dark matter within Higgs- and singlet-portal scenarios, models featuring (pseudo) Nambu-Goldstone bosons and two Higgs doublet extensions. One of the main conclusions of our work is that in a wide class of models the indirect constraints resulting from the measurements of the cross sections of $h_{125}$ provide substantially stronger constraints on the invisible Higgs-boson branching ratio compared to the direct limits obtained from searches for the invisible decay of $h_{125}$. However, we demonstrate that the presence of an invisible decay mode of $h_{125}$ can also open up parameter space regions which otherwise would be excluded as a result of the indirect constraints. As a byproduct of our analysis, we show that in light of the new results from the LZ collaboration a fermionic DM candidate within the simplest Higgs-portal scenario is ruled out under standard assumptions.