Sterile Neutrino Portal Dark Matter in $ν$THDM

Abstract

In this paper, we propose the sterile neutrino portal dark matter in νTHDM. This model can naturally generate tiny neutrino mass with the neutrinophilic scalar doublet Φ ν and sterile neutrinos N around TeV scale. Charged under a Z 2 symmetry, one Dirac fermion singlet χ and one scalar singlet φ are further introduced in the dark sector. The sterile neutrinos N are the mediators between the DM and SM. Depending on the coupling strength, the DM can be either WIMP or FIMP. For the WIMP scenario, pair annihilation of DM into N N is the key channel to satisfy various bounds, which could be tested at indirect detection experiments. For the FIMP scenario, besides the direct production of DM from freeze-in mechanism, contributions from late decay of NLSP is also important. When sterile neutrinos are heavier than the dark sector, NLSP is long-lived due to tiny mixing angle between sterile and light neutrinos. Constrains from free-streaming length, CMB, BBN and neutrino experiments are considered.