Regenerating a Symmetry in Asymmetric Dark Matter

TL;DR

This paper demonstrates that asymmetric dark matter models are largely incompatible with observational constraints unless a symmetry prevents particle-antiparticle mixing, due to oscillations and annihilation processes over cosmic timescales.

Contribution

It provides a comprehensive analysis showing that dark matter oscillations and annihilations challenge the viability of asymmetric dark matter models without additional symmetries.

Findings

Dark matter oscillations lead to symmetric particle-antiparticle mixing.

Efficient annihilation depletes primordial asymmetric dark matter.

Most asymmetric dark matter scenarios are ruled out unless symmetry forbids mixing.

Abstract

Asymmetric dark matter theories generically allow for mass terms that lead to particle-antiparticle mixing. Over the age of the Universe, dark matter can thus oscillate from a purely asymmetric configuration into a symmetric mix of particles and antiparticles, allowing for pair-annihilation processes. Additionally, requiring efficient depletion of the primordial thermal (symmetric) component generically entails large annihilation rates. We show that unless some symmetry completely forbids dark matter particle-antiparticle mixing, asymmetric dark matter is effectively ruled out for a large range of masses, for almost any oscillation time-scale shorter than the age of the Universe.