Speaker
Description
The singlet-doublet dark matter model is one of the most studied WIMP scenarios to realize the relic of DM in a large parameter space. In this work, we study the two-step leptogenesis in the singlet-doublet Majorana dark matter model. We extend the Standard Model (SM) by introducing three Majorana singlet fermions ($N_i$), three doublet fermions ($\Psi_i$), and a singlet scalar ($\Phi$), all of which are odd under an imposed $Z_2$ symmetry, while SM particles remain even.
The $CP$-violating out-of-decay of the heavier singlets ($N_{2,3}$) to the lighter doublets ($\Psi_i$) generates an asymmetry in the doublets. This asymmetry is then transferred to the lepton asymmetry via decays of $\Psi_i$ to leptons. Prior to the electro-weak (EW) symmetry breaking, this lepton asymmetry is converted to the baryon asymmetry by the EW spharelons. We also show that the imposed $Z_2$ symmetry prevents neutrino masses at tree level but allows them to be generated at one loop. Additionally, we analyze the dark matter relic, including the annihilation, co-annihilation, and co-scattering processes. We constrain the parameter space with the present direct, indirect, and collider searches.
