Upper Bounds on Asymmetric Dark Matter Self Annihilation Cross Sections

TL;DR

This paper derives bounds on dark matter self-annihilation rates in asymmetric dark matter models to prevent wash-out of the matter-antimatter asymmetry, analyzing coupled Boltzmann equations and applying constraints to specific scenarios.

Contribution

It provides a general framework for constraining dark matter self-annihilation cross sections in asymmetric models, including detailed conditions to avoid wash-out effects.

Findings

Large electroweak gaugino masses are required to suppress wash-out.

Very small mixing angles can prevent asymmetry wash-out.

Constraints are applicable to various dark matter scenarios.

Abstract

Most models for asymmetric dark matter allow for dark matter self annihilation processes, which can wash out the asymmetry at temperatures near and below the dark matter mass. We study the coupled set of Boltzmann equations for the symmetric and antisymmetric dark matter number densities, and derive conditions applicable to a large class of models for the absence of a significant wash-out of an asymmetry. These constraints are applied to various existing scenarios. In the case of left- or right-handed sneutrinos, very large electroweak gaugino masses, or very small mixing angles are required.