Thermal Relic Right-Handed Neutrino Dark Matter

It is known that two heavy Majorana right-handed neutrinos are sufficient to generate the baryon asymmetry in the present universe. Thus, it is interesting to identify the third right-handed neutrino N with the dark matter. We impose a new discrete symmetry Z2 on this dark matter neutrino to stabilize it. However, the U(1)B−L gauge boson A′ couples to the right-handed neutrino N. If the B−L breaking scale VB−L is sufficiently low, the dark matter neutrino N can be in the thermal bath. We find that the thermal relic N can explain the dark matter abundance for the B−L breaking scale VB−L∼O(10) TeV. After considering all the constraints from the existing experiments, a narrow mass region of the thermal produced right-handed neutrino dark matter N is still surviving.