Cosmological Bounds on Scotogenic Model with Asymmetric Mediator

TL;DR

This work analyzes cosmological bounds on the asymmetric mediator variant of the scotogenic model, where an eta mediator links the visible and dark sectors and a singlet sigma serves as DM. By solving Boltzmann equations that include eta decays and pre-freeze-out annihilations, the authors determine the DM relic abundance and impose BBN constraints from late eta decays. They find that successful cosmology requires tight control of the eta lifetime and the mu coupling, with viable mediator masses up to roughly 10 TeV and DM set near m_DM ~ 1.784 GeV by the BAU-to-DM relation. The results delineate a constrained parameter space where neutrino masses, DM, and BAU cohere without spoiling primordial element abundances. All mathematical relations are treated with appropriate notation, and the study emphasizes the interplay between asymmetric dark matter production and BBN as a powerful cosmological probe of scotogenic ADM scenarios.

Abstract

We study cosmological constraints on the asymmetric mediator scenario, a variant of the scotogenic model that addresses the origins of neutrino masses, dark matter (DM), and the baryon asymmetry. An SU(2)$_L$ doublet scalar $η$ mediates between the visible and dark sectors, while a singlet scalar $σ$ serves as the DM candidate. We evaluate the DM relic abundance by solving the Boltzmann equations including $η$ decay and scattering processes prior to the freeze-out of the $η$ asymmetry, and show Big Bang nucleosynthesis constraints from late-time $η$ decays. Combining the DM abundance and BBN bounds, we find the favored parameter space of this model, for instance, the mediator masses of $m_η\lesssim \mathcal{O}(10)$ TeV.

Figures (7)

• Figure 1: Lifetime of the charged scalar $\eta^+$ as a function of the mass difference.
• Figure 2: Charged $\eta$
• Figure 3: Neutral $\eta$
• Figure 5: Charged $\eta$
• Figure 6: Neutral $\eta$