Low-Scale Leptogenesis in the Scotogenic Neutrino Mass Model

TL;DR

This paper shows that the scotogenic model can generate the Universe's baryon asymmetry through low-scale leptogenesis, with a lower bound on right-handed neutrino masses around 10 TeV, making it experimentally testable.

Contribution

It demonstrates the feasibility of low-scale leptogenesis in the scotogenic model with three right-handed neutrinos without requiring degeneracy, and identifies key conditions for this mechanism.

Findings

Successful low-scale leptogenesis with three RHNs at around 10 TeV.

Low active neutrino mass (~10^-12 eV) needed for suppressed washout.

Leptogenesis testable via neutrino mass measurements.

Abstract

The scotogenic model proposed by Ernest Ma represents an attractive and minimal example for the generation of small Standard Model neutrino masses via radiative corrections in the dark matter sector. In this paper, we demonstrate that, in addition to neutrino masses and dark matter, the scotogenic model also allows to explain the baryon asymmetry of the Universe via low-scale leptogenesis. First, we consider the case of two right-handed neutrinos (RHNs) N_{1,2}, for which we provide an analytical argument why it is impossible to push the RHN mass scale below M_1^min ~ 10^10 GeV, which is identical to the value in standard thermal leptogenesis in the type-I seesaw scenario with the same washout strength. Then, we present a detailed study of the three-RHN case based on both an analytical and a numerical analysis. In the case of three RHNs, we obtain a lower bound on the N_1 mass of around 10 TeV. Remarkably enough, successful low-scale leptogenesis can be achieved without any degeneracy in the RHN mass spectrum. The only necessary condition is a suppression in the N_1 Yukawa couplings, which results in suppressed washout and a small active neutrino mass of around 10^-12 eV. This leads to the fascinating realization that low-scale leptogenesis in the scotogenic model can be tested in experiments that aim at measuring the absolute neutrino mass scale.