Large contributions to dark matter annihilation from three-body final states
Carlos E. Yaguna
TL;DR
The paper addresses the gap that traditional dark matter annihilation calculations largely ignore three-body final states with a real and a virtual massive particle, potentially biasing relic density and indirect detection predictions. It investigates the impact of $WW^*$ and $t\bar{t}^*$ final states in two well-motivated frameworks: the singlet scalar dark matter model and MSSM neutralinos, employing calculations that integrate these channels into cross sections and Boltzmann-equation analyses. The findings show that three-body contributions can reduce the relic density by factors up to more than 2 and can enhance present-day annihilation rates by up to two orders of magnitude, with the MSSM case exhibiting sizable but model-dependent effects below the top threshold. These results highlight the importance of including three-body final states in accurate DM phenomenology and motivate broader parameter studies and consideration of additional corrections in future work.
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.