Abstract
We constrain the Higgs-portal model employing the vector-boson fusion channel at the LHC. In particular, we include the phenomenologically interesting parameter region near the Higgs resonance, where the Higgs-boson mass is close to the threshold for dark-matter production and a running-width prescription has to be employed for the Higgs- boson propagator. Limits for the Higgs-portal coupling as a function of the dark-matter mass are derived from the CMS search for invisible Higgs-boson decays in vector-boson fusion at 13 TeV. Furthermore, we perform projections for the 14 TeV HL-LHC and the 27 TeV HE-LHC taking into account a realistic estimate of the systematic uncertainties. The respective upper limits on the invisible branching ratio of the Higgs boson reach a level of 2% and constrain perturbative Higgs-portal couplings up to dark-matter masses of about 110 GeV.
Highlights
MDM = mh/2 ± O(Γtot), where Γtot is the total Higgs width
Deviating even further from canonical assumptions, the coupling required by the relic density constraint can be largely altered by a nonstandard cosmological history [23], while direct detection limits can be relaxed in minimal extensions of the singlet scalar Higgs portal model [24,25,26]
Several Higgs production channels have been investigated in the past [30,31,32,33,34] and it has been shown that the vector-boson fusion (VBF) channel is the most sensitive one, motivating extensive studies of this channel in searches for invisible Higgs decays and Higgs-portal DM at current and future colliders [35,36,37,38,39,40,41]
Summary
We consider the scalar singlet Higgs-portal model [2,3,4], which is among the simplest possible UV-complete extensions of the SM. It extends the SM by a real singlet scalar field S that is stabilized by a Z2 symmetry and thereby provides a DM candidate. In unitary gauge we can write Φ = (0, h + v)/ 2, where v 246 GeV is the SM Higgs vacuum expectation value and the scalar mass is given by m2S = m2S,0 + λHPv2/2. Higgs-portal models, we refer the reader to the recent and comprehensive review ref.
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