| Summary: | Abstract We investigate the impact of interactions between hidden sectors and the discovered Higgs boson $$h_{125}$$ h 125 , allowing for additional invisible decay channels of $$h_{125}$$ h 125 . We perform $$\chi ^2$$ χ 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 $$h_{125}$$ 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 $$h_{125}$$ 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 $$h_{125}$$ 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 $$h_{125}$$ h 125 . However, we demonstrate that the presence of an invisible decay mode of $$h_{125}$$ 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.
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