Abstract
We identify regions in a Type-II two-Higgs-doublet model which correspond to a metastable electroweak vacuum with lifetime larger than the age of the universe. We analyse scenarios which retain perturbative unitarity up to grand unification and Planck scales. Each point in the parameter space is restricted using data from the Large Hadron Collider (LHC) as well as flavour and precision electroweak constraints. We find that substantial regions of the parameter space are thus identified as corresponding to metastability, which complement the allowed regions for absolute stability, for top quark mass at the high as well as low end of its currently allowed range. Thus, a two-Higgs-doublet scenario with the electroweak vacuum, either stable or metastable, can sail through all the way up to the Planck scale without facing any contradiction.
Highlights
Mh[GeV] > 129.4 + 1.4Mt [GeV] − 173.1 0.7− 0.5 αs(MZ ) − 0.1184 0.0007 ± 1.0th. (1.1)Here, Mt is the top quark pole mass
We showed in the context of a Type-II 2HDM that the EW vacuum can be rendered stable till the Planck scale even for a top pole mass at the high end of the allowed band [7]
Model points that successfully negotiate all the aforesaid constraints are allowed to evolve under renormalisation group (RG), till some scale. can be interpreted as the scale up to which no physics over and above the extended Higgs sector is required
Summary
As has already been mentioned, a 2HDM (of, say, Type II) allows enough of parameter space with a stable vacuum, without any new physics all the way up to the Planck scale, even if the top mass is at its upper limit. The investigation in this direction becomes complete only after checking whether and how the allowed region expands, once the possibility of a metastable electroweak vacuum is taken into account.
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