Higgs-boson visible and invisible constraints on hidden sectors

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.