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

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 the singlet-doublet mass splitting Δ M , the singlet-doublet mixing angle sin θ , and the DM mass M DM . If the DM is assumed to be of Dirac nature, then the annihilation, coannihilation, and conversion driven processes combined allow a range of parameter space: 100 GeV ≲ M DM ≲ 750 GeV and 10 − 6 ≲ sin θ ≲ 0.04 for Δ M > 1 GeV . While the nature of DM, either Dirac or Majorana, is not known, in this work, we assume the singlet-doublet DM to be of Majorana type and find that the relic density and direct detection can be satisfied over a larger parameter space. In particular, the allowed ranges of DM mass and sin θ are 100 GeV ≲ M DM ≲ 1750 GeV and 2 × 10 − 7 ≲ sin θ ≲ 0.45 for Δ M > 1 GeV .