Majorana Dark Matter and Neutrino mass in a singlet-doublet extension of the Standard Model

TL;DR

This paper proposes a minimal extension of the Standard Model with a vector-like fermion doublet and three right-handed neutrinos to explain dark matter and neutrino masses, highlighting a Majorana dark matter candidate that evades direct detection constraints.

Contribution

It introduces a novel singlet-doublet extension with Majorana dark matter and demonstrates its viability through relic density and direct search analysis.

Findings

Majorana dark matter evades Z-mediated direct detection constraints.

The model successfully explains neutrino masses via Type-I Seesaw.

Parameter space consistent with relic density and experimental bounds identified.

Abstract

A minimal extension of the Standard Model (SM) by a vector-like fermion doublet and three right handed (RH) singlet neutrinos is proposed in order to explain dark matter and tiny neutrino mass simultaneously. The DM arises as a mixture of the neutral component of the fermion doublet and one of the RH neutrinos, both assumed to be odd under an imposed $\mathcal{Z}_2$ symmetry. Being Majorana in nature, the DM escapes from $Z$-mediated direct search constraints to mark a significant difference from singlet-doublet Dirac DM. The other two $\mathcal{Z}_2$ even heavy RH neutrinos give rise masses and mixing of light neutrinos via Type-I Seesaw mechanism. Relic density and direct search allowed parameter space for the model is investigated through detailed numerical scan.