Bounds on Higgs-Portal models from the LHC Higgs data

Abstract

In a number of Higgs-portal models, an $SU(2)$ isospin-singlet scalar boson generically appears at the electroweak scale and can mix with the Standard Model (SM) Higgs boson with a mixing angle $\alpha$. This singlet scalar boson can have renormalizable couplings to a pair of dark matter particles, vectorlike leptons or quarks, or new gauge bosons, thereby modifying the Higgs signal strengths in a nontrivial way. In this work, we perform global fits to such models using the most updated LHC Higgs-boson data and discuss the corresponding implications on Higgs-portal-type models. In particular we find that the current LHC Higgs-boson data slightly favors the SM over the Higgs-portal singlet-scalar models, which has to be further examined using the upcoming LHC Higgs-boson data. Finally the Higgs-portal models are constrained as follows: $\cos\alpha \gtrsim 0.86$ and $\Delta \Gamma_{\rm tot} \lesssim 1.9$ MeV at 95 \% CL.