Sterile Neutrino Dark Matter and Leptogenesis in Left-Right Higgs Parity

TL;DR

This paper explores a Left-Right symmetric model with Higgs Parity that naturally explains sterile neutrino dark matter and baryogenesis via leptogenesis, linking the symmetry breaking scale to the Higgs quartic coupling's vanishing point.

Contribution

It introduces a unified framework where right-handed neutrino dark matter and leptogenesis occur at the symmetry breaking scale, connecting cosmology with Higgs physics and neutrino properties.

Findings

Dark matter abundance consistent with freeze-out and freeze-in scenarios.

Leptogenesis successfully generates baryon asymmetry within the model.

Parameter space aligns with the Higgs quartic coupling vanishing scale.

Abstract

The standard model Higgs quartic coupling vanishes at $(10^{9}-10^{13})$ GeV. We study $SU(2)_L \times SU(2)_R \times U(1)_{B-L}$ theories that incorporate the Higgs Parity mechanism, where this becomes the scale of Left-Right symmetry breaking, $v_R$. Furthermore, these theories solve the strong CP problem and predict three right-handed neutrinos. We introduce cosmologies where $SU(2)_R \times U(1)_{B-L}$ 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 $v_R$ to be in the range $(10^{10}-10^{13})$ GeV for freeze-out, in remarkable agreement with the scale where the Higgs quartic coupling vanishes, whereas freeze-in requires $v_R \gtrsim 10^9$ 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.