High scale validity of two Higgs doublet scenarios with a real scalar singlet dark matter

TL;DR

This paper investigates the high-scale validity of two Higgs doublet models with a scalar singlet dark matter candidate, finding that Type-X models can be valid up to the Planck scale while Type-II models are limited to around 10^6 GeV, with implications for collider detection.

Contribution

It provides a detailed analysis of the high-scale validity of Type-II and Type-X 2HDMs with scalar singlet dark matter, including constraints from unitarity, stability, and relic density, highlighting their differing cutoff scales.

Findings

Type-II 2HDM with scalar DM has a cutoff around 10^6 GeV.

Type-X 2HDM with scalar DM can be valid up to the Planck scale.

Parameter regions in Type-X are detectable at the High-luminosity LHC.

Abstract

We study the high-scale validity of two kinds of two Higgs doublet models (2HDM), namely, Type-II and Type-X, but with a scalar SU(2) singlet dark matter (DM) candidate in addition in each case. The additional quartic couplings involving the DM particle in the scalar potential in both the scenarios bring in additional constraints from the requirement of perturbative unitarity and vacuum stability. DM relic density and direct search constraints play a crucial role in this analysis as the perturbative unitarity of the DM-Higgs portal couplings primarily decide the high scale validity of the model. We find that, within the parameter regions thus restricted, the Type-II scenario must have a cut-off at around $10^6$ GeV, while the Type-X scenario admits of validity upto the Planck scale. However, only those regions which are valid upto about $10^8$ GeV in Type-X 2HDM is amenable to detection at the High-luminosity LHC (upto 3000 $fb^{-1}$), while most of the parameter space of the Type-II scenario mentioned above is likely to be detectable.