Spontaneous CP violation, sterile neutrino dark matter, and leptogenesis

TL;DR

This paper presents a five-dimensional model that addresses the strong CP problem, explains dark matter as a light right-handed neutrino, and accounts for baryon asymmetry via leptogenesis, integrating spontaneous CP violation and extra-dimensional localization.

Contribution

It introduces a novel five-dimensional framework with spontaneous CP violation, linking dark matter, leptogenesis, and the strong CP problem in a unified model.

Findings

Lightest right-handed neutrino as 10 keV dark matter with correct relic density

Heavy neutrinos generate baryon asymmetry through leptogenesis

Wave-function localization suppresses dangerous operators and explains small neutrino masses

Abstract

We constructed a model for spontaneous CP symmetry breaking in five-dimensional space-time that has a potential to solve the strong CP problem. To explain the nature of dark matter and the baryon asymmetry of the universe, three right-handed neutrinos and $U(1)_{B-L}$ gauge interaction are introduced in the bulk, in addition to the field contents of the Bento-Branco-Parada model. The wave-function profiles in the fifth dimension can suppress dangerous operators allowed by symmetries, and the scale of spontaneous CP symmetry breaking can be sufficiently large to be consistent with thermal leptogenesis. In this model, the lightest right-handed neutrino serves as dark matter with a mass of $\mathcal{O}(10)$ keV. This small mass and the necessarily small mixing are explained by the exponentially localized wave-function in the fifth dimension due to a bulk mass term. The correct relic abundance is achieved thanks to the $U(1)_{B-L}$ gauge interaction. The other heavy right-handed neutrinos explain the baryon asymmetry of the universe through leptogenesis, with the required CP violating phases generated by interactions involving heavy leptons.