Large contributions to dark matter annihilation from three-body final states

TL;DR

This paper demonstrates that three-body final states significantly enhance dark matter annihilation rates, affecting relic density predictions and indirect detection signals, with potential increases up to two orders of magnitude.

Contribution

It introduces large three-body final state contributions to dark matter annihilation rates, a novel factor not previously considered in relic density and detection calculations.

Findings

Relic density predictions can decrease by more than a factor of two.

Dark matter annihilation rates can be enhanced by up to two orders of magnitude.

Three-body final states are significant in models like the singlet and MSSM.

Abstract

The annihilation rate of dark matter particles plays a crucial role in dark matter studies, for it determines their relic density and their indirect detection signal. In this paper, we show that this annihilation rate can receive large additional contributions from three-body final states consisting of a real and a virtual massive particle, such as WW* (Wf \bar f') and t \bar t* (tW\bar b). We consider two specific examples, from the singlet model and the MSSM, and find that, due to the new three-body final state contributions, the prediction for the relic density may decrease by more than a factor two, whereas the present dark matter annihilation rate gets enhanced by up to two orders of magnitude. Some of the implications of these results are briefly discussed.