Baryogenesis and Dark Matter from light Sterile Neutrinos

TL;DR

This paper introduces a minimal mechanism where light sterile neutrinos can explain both the Universe's baryon asymmetry and dark matter, linking high-temperature Dirac behavior to low-temperature dark matter viability.

Contribution

It presents a novel, flexible framework connecting sterile neutrino properties to baryogenesis and dark matter, including detailed phenomenological analysis and specific ultraviolet completions.

Findings

Sterile neutrinos can account for baryon asymmetry and dark matter simultaneously.

The model is consistent with cosmological and astrophysical constraints.

Two ultraviolet completions demonstrate the model's feasibility.

Abstract

We propose a simple and flexible mechanism by which sterile neutrinos with masses below the electroweak scale can simultaneously account for the observed baryon asymmetry of the Universe and the dark matter abundance. Crucially, neutrinos in this mass range behave as Dirac particles at high temperatures, allowing connections to Dirac leptogenesis, while at low temperatures, they can serve as viable warm dark matter candidates. We first perform a general analysis, assuming that unspecified ultraviolet dynamics generate both symmetric and asymmetric sterile-neutrino abundances before decoupling. Treating these abundances as initial conditions for the subsequent evolution allows us to systematically explore the phenomenologically viable regions of the low-energy parameter space, taking into account cosmological and astrophysical constraints, as well as implications for light-neutrino mass generation. Finally, we illustrate the model-building opportunities enabled by this minimal setup by studying two specific ultraviolet completions.