Singlet-Doublet Dirac Dark Matter

TL;DR

This paper explores a minimal extension of the Standard Model where a Dirac fermion dark matter candidate, composed of singlet and doublet components, is constrained by direct detection and relic density considerations, with specific mass and coupling bounds.

Contribution

It introduces a simple singlet-doublet Dirac fermion dark matter model with explicit parameter constraints and demonstrates its viability within extended Standard Model frameworks.

Findings

Dark matter mass below 750 GeV

Mass difference cannot exceed 9%

Direct detection experiments are most promising for probing this model

Abstract

We analyze a simple extension of the Standard Model where the dark matter particle is a Dirac fermion that is mixture of a singlet and an SU(2) doublet. The model contains only four free parameters: the singlet and the doublet masses and two new Yukawa couplings. Direct detection bounds in this model are very strong and require the dark matter particle to be singlet-like. As a result, its relic density has to be obtained via coannihilations with the doublet. We find that the dark matter mass should be below 750 GeV, that the singlet-doublet mass difference cannot exceed 9%, and that direct detection experiments offer the best chance to probe this scenario. Finally, we also show that this model can effectively arise in well-motivated extensions of the Standard Model.