Low Energy INTEGRAL Positrons from eXciting Dark Matter

TL;DR

This paper investigates whether eXciting Dark Matter (XDM) can explain the INTEGRAL 511 keV positron signal, showing that dark matter interactions could produce the observed positron rate through upscattering and de-excitation processes.

Contribution

It provides numerical calculations of dark matter upscattering cross sections considering baryonic effects, highlighting the significance of higher partial waves in the process.

Findings

Dark matter can produce the observed positron rate (~10^43 e^+/s)

Higher partial waves significantly contribute to the scattering cross section

XDM scenario is a viable explanation for the INTEGRAL positron signal

Abstract

The origin of the e^+e^- 511 keV line observed by INTEGRAL remains unclear. The rate and morphology of the signal have prompted questions as to whether dark matter could play a role. We explore the case of dark matter upscattering in the framework of eXciting Dark Matter (XDM), where WIMPs \chi, interacting through a new dark force, scatter into excited states \chi*, which subsequently emit e^+e^- pairs when they de-excite. We numerically compute the cross sections for two Yukawa-coupled DM particles upscattering into excited states, specifically considering variations motivated by recent N-body simulations with additional baryonic physics. We find that that l>0 components of the partial-wave decomposition are often significant contributions to the total cross section and that for reasonable ranges of parameters dark matter can produce the ~10^43 e^+/s observed by INTEGRAL.