Cogenesis of visible and dark matter in a scotogenic model

Within a scotogenic neutrino mass model we explore the cogenesis of matter from the CP violating decay of a heavy $\mathbb{Z}_2$-odd right handed neutrino that simultaneously populates the visible and a multipartite dark sector. The relic density of a sub-GeV scale freeze-in dark matter is generated by the late time decay of the next-to-lightest dark particle dynamically regulated by an interplay with the thermal scattering processes. We show that this model can simultaneously explain visible matter asymmetry and provide a cosmologically viable sub-GeV dark matter while remaining in consonance with the neutrino parameters and flavour observables.

💡 Research Summary

In this work the authors present a novel “cogenesis” framework built upon the minimal scotogenic model, in which the same CP‑violating decay of a heavy Z₂‑odd right‑handed neutrino (denoted N₂) simultaneously generates the observed baryon asymmetry and a multipartite dark sector. The model extends the Standard Model by a Z₂‑odd inert scalar doublet η and three right‑handed neutrinos N₁, N₂, N₃ with a hierarchical mass spectrum M₃ ≫ M₂ ≫ M₁. The Yukawa interaction L ⊃ Y_{αi} \bar L_α η N_i, together with the scalar potential containing λ₅, induces neutrino masses radiatively at one loop. The λ₅ term splits the neutral components of η, linking the neutrino sector directly to dark‑matter phenomenology.

Cogenesis proceeds as follows. The heavy N₂ decays out of equilibrium via N₂ → ℓ η. Because the Yukawa couplings are complex, the interference between tree‑level and one‑loop diagrams yields a CP asymmetry ε (Eq. 3.1) proportional to Im