Co-Decaying Dark Matter

TL;DR

This paper introduces Co-Decaying Dark Matter, a novel thermal freezeout mechanism where dark matter density is reduced via out-of-equilibrium decays of nearly degenerate particles, predicting enhanced indirect detection signals.

Contribution

It presents a new co-decay mechanism for dark matter relic abundance, including a simple model implementation and implications for indirect detection.

Findings

Dark matter relic density can be set by decay processes rather than Boltzmann suppression.

The mechanism predicts boosted annihilation cross-sections and enhanced indirect detection signals.

A viable parameter space exists for this co-decay scenario.

Abstract

We propose a new mechanism for thermal dark matter freezeout, termed Co-Decaying Dark Matter. Multi-component dark sectors with degenerate particles and out-of-equilibrium decays can co-decay to obtain the observed relic density. The dark matter density is exponentially depleted through the decay of nearly degenerate particles, rather than from Boltzmann suppression. The relic abundance is set by the dark matter annihilation cross-section, which is predicted to be boosted, and the decay rate of the dark sector particles. The mechanism is viable in a broad range of dark matter parameter space, with a robust prediction of an enhanced indirect detection signal. Finally, we present a simple model that realizes co-decaying dark matter.