Two dark matter candidates in three-Higgs-doublet models with $S_3$ symmetry

TL;DR

This paper explores $S_3$-symmetric three-Higgs-doublet models, identifying potential dark matter candidates stabilized by a residual $ ext{Z}_2$ symmetry, with candidate masses in specific ranges, and compares models with and without CP violation.

Contribution

It systematically catalogs $S_3$-symmetric three-Higgs-doublet models, analyzing their vacuum structures and identifying viable dark matter candidates with distinct mass ranges.

Findings

Dark matter candidate masses range between 52.5-89 GeV with CP violation.

Dark matter candidate masses range between 6.5-44.5 GeV without CP violation.

Models can have vacua with one or two vanishing vacuum expectation values.

Abstract

Models with an extended scalar electroweak sector can have vanishing vacuum expectation values in a basis where an underlying symmetry is imposed. Such extensions are very well motivated. If a symmetry prevents couplings between fermions and additional scalars, such scalars could become viable dark matter candidates if some additional criteria are satisfied. We catalogue $S_3$-symmetric three-Higgs-doublet models, also allowing for softly broken $S_3$-symmetric scalar potential terms, based on whether a specific model could possibly accommodate a dark matter candidate. The variety of the $S_3$-symmetric family models arises due to different possibilities to arrange vacuum expectation values. Such models can have vacua with one or two vanishing vacuum expectation values. In our study we assume that the dark matter candidate is stabilised by the $\mathbb{Z}_2$ symmetry. The $\mathbb{Z}_2$ symmetry is a remnant of $S_3$ symmetry which survived spontaneous symmetry breaking, and not superimposed over $S_3$. We explore two models; with an without CP violation. These models have a single dark and two active scalar sectors. The active sectors behave in many aspects like a Type-I two-Higgs-doublet model. The dark matter candidate masses, in two cases, are different from the known (previously studied) models with three scalar doublets. After investigating the models in detail, identifying parameters compatible with both theoretical and experimental constraints, we found that the dark matter candidate mass could be within the range of $[52.5,\,89]~\text{GeV}$ or $[6.5,\,44.5]~\text{GeV}$ for a model with CP violation.