Asymmetric Dark Matter via Spontaneous Co-Genesis

TL;DR

This paper proposes a new mechanism for the simultaneous generation of dark matter and baryon asymmetries through a light scalar field, explaining their observed density ratio and providing a pathway for symmetric DM annihilation.

Contribution

It introduces a spontaneous co-genesis mechanism involving a light scalar field that links dark matter and baryon asymmetries, a novel approach in asymmetric dark matter models.

Findings

Mechanism explains the observed Omega_DM/Omega_B ratio of ~5.

Scalar field phi couples derivatively to dark matter, acting like a dark axion.

Residual symmetric dark matter can annihilate into the scalar field.

Abstract

We investigate, in the context of asymmetric dark matter (DM), a new mechanism of spontaneous co-genesis of linked DM and baryon asymmetries, explaining the observed relation between the baryon and DM densities, Omega_DM/Omega_B ~ 5. The co-genesis mechanism requires a light scalar field, phi, with mass below 5 eV which couples derivatively to DM, much like a `dark axion'. The field phi can itself provide a final state into which the residual symmetric DM component can annihilate away.