Unified Origin of Dark Matter Self-Interactions and Low Scale Leptogenesis

TL;DR

This paper introduces a minimal model linking dark matter self-interactions with low-scale leptogenesis, using a scotogenic seesaw scenario where a light scalar mediates DM interactions and enhances CP asymmetry, explaining neutrino masses and baryon asymmetry.

Contribution

It presents a unified framework where a single scalar field facilitates dark matter self-interactions and enhances leptogenesis, with a minimal particle content in a scotogenic seesaw model.

Findings

Dark matter self-interactions alleviate small-scale structure issues.

Enhanced CP asymmetry from scalar-mediated decay processes.

Model is testable via dark matter detection, flavor physics, and collider experiments.

Abstract

We propose a novel and minimal framework where a light scalar field can give rise to dark matter (DM) self-interactions, while enhancing the CP symmetry required for successful baryon asymmetry of the Universe via leptogenesis route. For demonstration purpose we choose to work in a scotogenic seesaw scenario where the lightest among the right handed neutrinos (RHN), introduced for generating light neutrino masses radiatively, play the role of DM while the heavier two can play non-trivial roles in generating DM relic as well as lepton asymmetry. While dark matter self-interactions mediated by an additional singlet scalar can alleviate the small scale issues of cold dark matter paradigm, the same scalar can give rise to new one-loop decay processes of heavy RHN into standard model leptons providing an enhanced contribution to CP asymmetry, even with sub-TeV scale RHN mass. The thermally under-abundant relic of DM due to large annihilation rates into its light mediator receives a late non-thermal contribution from a heavier RHN. With only five new particles involved in the scotogenic seesaw, each having non-trivial roles in generating DM relic and baryon asymmetry, the model can explain non-zero neutrino mass while being verifiable at different experiments related to DM direct detection, flavour physics and colliders. The mechanism we demonstrated here by using a scotogenic seesaw scenario is also applicable to other models.