Sterile neutrino dark matter and leptogenesis in Left-Right Higgs Parity

Abstract

The standard model Higgs quartic coupling vanishes at (109 − 1013) GeV. We study SU(2)L× SU(2)R× U(1)B−L theories that incorporate the Higgs Parity mechanism, where this becomes the scale of Left-Right symmetry breaking, vR. Furthermore, these theories solve the strong CP problem and predict three right-handed neutrinos. We introduce cosmologies where SU(2)R× U(1)B−L gauge interactions produce right-handed neutrinos via the freeze-out or freeze-in mechanisms. In both cases, we find the parameter space where the lightest right-handed neutrino is dark matter and the decay of a heavier one creates the baryon asymmetry of the universe via leptogenesis. A theory of flavor is constructed that naturally accounts for the lightness and stability of the right-handed neutrino dark matter, while maintaining sufficient baryon asymmetry. The dark matter abundance and successful natural leptogenesis require vR to be in the range (1010− 1013) GeV for freeze-out, in remarkable agreement with the scale where the Higgs quartic coupling vanishes, whereas freeze-in requires vR ≳ 109 GeV. The allowed parameter space can be probed by the warmness of dark matter, precise determinations of the top quark mass and QCD coupling by future colliders and lattice computations, and measurement of the neutrino mass hierarchy.