Sommerfeld Effect and Bound State Formation for Dark Matter Models with Colored Mediators with SE+BSF4DM

TL;DR

This paper investigates the impact of Sommerfeld effect and bound state formation on dark matter relic abundance calculations in models with colored mediators, providing a practical computational tool for the community.

Contribution

It introduces an automated method and software add-on for including Sommerfeld and bound state effects in dark matter relic density computations within t-channel models.

Findings

Sommerfeld and bound state effects can significantly alter DM mass constraints.

The effects are model-dependent but can cause order-one corrections.

The paper provides a publicly available computational tool for these effects.

Abstract

In the universal framework of simplified $t$-channel dark matter models, the calculation of the relic abundance can be dominated by mediator annihilation when the dark matter and mediator masses are almost degenerate. We analyze four representative models with scalar and fermionic mediators, confront them with direct detection limits and highlight the differences and common features between them. The mediator annihilations are considerably enhanced by the Sommerfeld effect and bound state formation. Albeit their effect is subdominant in the coannihilation regime, excited bound state levels are included as well. We find that Sommerfeld and bound-state effects can lead to order one corrections to the constraints on the DM mass in the coannihilating regime, with the precise magnitude depending on the specific model realization. In addition we provide SE+BSF4DM, an intuitive and easy to use add-on to micrOMEGAs, allowing for an automated inclusion of these effects for a generic $t$-channel Dark Matter Model, which is publicly available on Github.