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

Understand

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.