Sommerfeld enhancement of resonant dark matter annihilation

TL;DR

This paper demonstrates that the combined Sommerfeld and resonant enhancements in dark matter annihilation factorize, simplifying the analysis of their joint effects, and explores their implications in specific dark matter models.

Contribution

It shows that when both enhancements are present, all non-factorizable effects cancel at leading order, providing a clearer understanding of their combined impact.

Findings

Enhancement effects factorize when both are present.

Leading order non-factorizable effects cancel out.

Implications for Higgs portal and MSSM-inspired models.

Abstract

The dark matter annihilation cross section can be amplified by orders of magnitude if the annihilation occurs into a narrow resonance, or if the dark-matter particles experience a long-range force before annihilation (Sommerfeld effect). We show that when both enhancements are present they factorize completely, that is, all long-distance non-factorizable effects cancel at leading order in the small-velocity and narrow-width expansion. We then investigate the viability of ``super-resonant'' annihilation from the coaction of both mechanisms in Standard Model Higgs portal and simplified MSSM-inspired dark-matter scenarios.