Sterile Neutrino Portal Dark Matter in $\nu$THDM

TL;DR

This paper introduces a sterile neutrino portal dark matter model within the $ u$THDM framework, explaining tiny neutrino masses and exploring WIMP and FIMP dark matter scenarios with potential experimental tests.

Contribution

It proposes a novel sterile neutrino portal dark matter model in $ u$THDM, detailing mechanisms for WIMP and FIMP dark matter production and their experimental implications.

Findings

WIMP annihilation into $NN$ can satisfy observational bounds

FIMP production includes freeze-in and late decay contributions

Constraints from cosmology and neutrino experiments are analyzed

Abstract

In this paper, we propose the sterile neutrino portal dark matter in $\nu$THDM. This model can naturally generate tiny neutrino mass with the neutrinophilic scalar doublet $\Phi_{\nu}$ and sterile neutrinos $N$ around TeV scale. Charged under a $Z_2$ symmetry, one Dirac fermion singlet $\chi$ and one scalar singlet $\phi$ 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 $NN$ 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.