DRAKE: Dark matter Relic Abundance beyond Kinetic Equilibrium

TL;DR

DRAKE is a numerical tool that accurately predicts dark matter relic abundance beyond the assumption of kinetic equilibrium, addressing complex scenarios like resonance and Sommerfeld effects that can significantly alter relic density estimates.

Contribution

The paper introduces DRAKE, a novel numerical tool with multiple Boltzmann solvers for precise relic density calculations in non-standard kinetic decoupling scenarios.

Findings

Traditional methods can misestimate relic density by up to an order of magnitude.

DRAKE accurately models complex annihilation processes like resonance and Sommerfeld effects.

The tool is publicly available with example applications.

Abstract

We introduce DRAKE, a numerical precision tool for predicting the dark matter relic abundance also in situations where the standard assumption of kinetic equilibrium during the freeze-out process may not be satisfied. DRAKE comes with a set of three dedicated Boltzmann equation solvers that implement, respectively, the traditionally adopted equation for the dark matter number density, fluid-like equations that couple the evolution of number density and velocity dispersion, and a full numerical evolution of the phase-space distribution. We review the general motivation for these approaches and, for illustration, highlight three concrete classes of models where kinetic and chemical decoupling are intertwined in a way that quantitatively impacts the relic density: i) dark matter annihilation via a narrow resonance, ii) Sommerfeld-enhanced annihilation and iii) `forbidden' annihilation to final states that are kinematically inaccessible at threshold. We discuss all these cases in some detail, demonstrating that the commonly adopted, traditional treatment can result in an estimate of the relic density that is wrong by up to an order of magnitude. The public release of DRAKE, along with several examples of how to calculate the relic density in concrete models, is provided at drake.hepforge.org