Cosmological Bounds on Scotogenic Model with Asymmetric Mediator

TL;DR

This paper investigates cosmological constraints on a variant of the scotogenic model involving an asymmetric mediator, focusing on dark matter relic abundance, neutrino masses, and baryon asymmetry, with implications for mediator mass scales.

Contribution

It introduces and analyzes the asymmetric mediator scenario within the scotogenic model, incorporating Boltzmann equations and BBN constraints to identify viable parameter space.

Findings

Mediator masses up to around 10 TeV are consistent with cosmological constraints.

Late-time $ ext{eta}$ decays impose significant BBN constraints.

The model successfully explains neutrino masses, dark matter, and baryon asymmetry within certain parameter ranges.

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 $\eta$ mediates between the visible and dark sectors, while a singlet scalar $\sigma$ serves as the DM candidate. We evaluate the DM relic abundance by solving the Boltzmann equations including $\eta$ decay and scattering processes prior to the freeze-out of the $\eta$ asymmetry, and show Big Bang nucleosynthesis constraints from late-time $\eta$ decays. Combining the DM abundance and BBN bounds, we find the favored parameter space of this model, for instance, the mediator masses of $m_\eta \lesssim \mathcal{O}(10)$ TeV.