Self-resonant Dark Matter

TL;DR

This paper introduces a new mechanism for Sommerfeld enhancement in dark matter interactions that does not require light mediators, using a two-component dark matter model with a triple coupling leading to an $u$-channel resonance.

Contribution

It presents the first derivation of the Sommerfeld factor from the elastic scattering of dark matter components via a Bethe-Salpeter equation with a delay term.

Findings

Identifies an $u$-channel resonance in dark matter elastic scattering.

Derives a Bethe-Salpeter equation with a delay term for the first time.

Discusses implications for dark matter self-scattering and annihilation.

Abstract

We present a novel mechanism for Sommerfeld enhancement for dark matter interactions without the need for light mediators. Considering a model for two-component dark matter with a triple coupling, we find that one of dark matter particles leads to an $u$-channel resonance in dark matter elastic scattering. From the sum of the $u$-channel ladder diagrams, we obtain a Bethe-Salpeter equation with a delay term and identify the Sommerfeld factor from the elastic scattering of two dark matter components for the first time. We discuss the implications of our results for enhancing dark matter self-scattering and annihilation.