Impact of conversion-driven processes on singlet-doublet Majorana dark matter relic

TL;DR

This paper investigates how conversion-driven processes influence the relic density of singlet-doublet Majorana dark matter, expanding the viable parameter space compared to Dirac dark matter scenarios.

Contribution

It demonstrates that assuming Majorana nature for singlet-doublet dark matter broadens the allowed parameter space for relic density and direct detection constraints.

Findings

Relic density and direct detection constraints are satisfied over larger parameter ranges for Majorana DM.

Allowed DM mass extends up to 1750 GeV for Majorana DM, compared to 750 GeV for Dirac DM.

Parameter space for mixing angle $ heta$ is significantly larger in the Majorana case.

Abstract

The singlet-doublet dark matter model offers a rich framework for exploring the nature of dark matter (DM) through its unique fermion structure. In this model, the important parameters are singlet-doublet mass splitting $\Delta{M}$, singlet-doublet mixing angle $\sin\theta$, and DM mass $M_{\rm DM}$. If the DM is assumed to be of Dirac nature, then the annihilation, co-annihilation, and conversion driven processes combinedly allows a range of parameter space: $1~{\rm GeV} \lesssim M_{\rm DM}\lesssim750$ GeV and $10^{-6}\lesssim\sin\theta\lesssim0.04$ for all $\Delta{M}>1$ GeV. While the nature of DM either Dirac or Majorana is not known, in this work we assume the nature of singlet-doublet DM to be of Majorana type and find that the relic density and direct detection can be satisfied in a larger parameter space. In particular, the allowed ranges of DM mass and $\sin\theta$ are: $1~{\rm GeV}\lesssim M_{\rm DM}\lesssim1750$ GeV and $2\times10^{-7}\lesssim\sin\theta\lesssim0.16$ for all $\Delta{M}>1$ GeV.