We study the possibility of right-handed neutrino dark matter (DM) in gauged U (1) B−L × Z 2 extension of the standard model augmented by an additional scalar doublet, being odd under the Z 2 symmetry, to give rise to the scotogenic scenario of radiative neutrino masses. Due to lepton portal interactions, the right-handed neutrino DM can have additional co-annihilation channels apart from the usual annihilations through Z B−L which give rise to much more allowed mass of DM from relic abundance criteria, even away from the resonance region like M DM ≈ M Z B−L /2. This enlarged parameter space is found to be consistent with neutrino mass constraints while being sensitive to direct detection experiments of DM as well as rare decay experiments looking for charged lepton flavour violating decays like µ → eγ. Due to the possibility of the Z 2 odd scalar doublet being the next to lightest stable particle that can be sufficiently produced in colliders by virtue of its gauge interactions, one can have interesting signatures like displaced vertex or disappearing charged tracks provided that the mass splitting δM between DM and the next to lightest stable particle (NLSP) is small. In particular, we show that if δM < m τ = 1.77 GeV, then get large displaced vertex signature of NLSP while being consistent with neutrino mass, lepton flavour violation and observed relic density.

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We propose an extension of the standard model with U (1)B−L × Z2 symmetry. In this model by assuming that the neutrinos are Dirac (i.e. B − L is an exact symmetry), we found a simultaneous solution for non zero neutrino masses and dark matter content of the universe. The observed baryon asymmetry of the universe is also explained using Dirac Leptogenesis, which is assisted by a dark sector, gauged under a U (1)D symmetry. The latter symmetry of the dark sector is broken at a TeV scale and thereby giving mass to a neutral gauge boson ZD. The standard model Z-boson mixes with the gauge boson ZD at one loop level and paves a way to detect the dark matter through spin independent elastic scattering at terrestrial laboratories.

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We propose an extension of the standard model (SM) by including a dark sector comprising of three generations of heavy right-handed neutrinos, a singlet scalar and a singlet Dirac fermion, where the latter two particles are stable and are viable candidates of dark matter (DM). In the early Universe, the CP-violating out-of-equilibrium decay of heavy right-handed neutrinos to singlet Dirac fermion and scalar in the dark sector generates a net DM asymmetry. The latter is then transported to the visible sector via a dimension eight operator which conserves B − L symmetry and is in thermal equilibrium above the sphaleron decoupling temperature. An additional light singlet scalar is introduced which mixes with the SM Higgs and pave a path for annihilating the symmetric components of the DM candidates. Then we discuss the constraints on singlet-doublet Higgs mixing from invisible Higgs decay, signal strength at LHC and direct search of DM at terrestrial laboratories. At tree level the neutrinos are shown to be massless since the symmetry of dark sector forbids the interaction of right-handed neutrinos with the SM particles. However, at one loop level the neutrinos acquire sub-eV masses as required by the oscillation experiments.