Two dark matter candidates in three-Higgs-doublet models with S3 symmetry

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 𝑆3-symmetric three-Higgs-doublet models, also allowing for softly broken 𝑆3-symmetric scalar potential terms, based on whether a specific model could possibly accommodate a dark matter candidate. The variety of the 𝑆3-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 Z2 symmetry. The Z2 symmetry is a remnant of 𝑆3 symmetry which survived spontaneous symmetry breaking, and not superimposed over 𝑆3. 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] GeV or [6.5, 44.5] GeV for a model with CP violation.