Cold Positrons from Decaying Dark Matter

TL;DR

This paper investigates how decaying dark matter particles could produce positrons that contribute to the 511 keV gamma-ray flux observed by INTEGRAL, providing constraints and potential explanations for the signal.

Contribution

It explores the scenario where dark matter decay produces positrons with a lifetime shorter than the universe's age, linking particle physics models to astrophysical observations.

Findings

Positron production from dark matter decay can explain the INTEGRAL 511 keV signal.

The model constrains dark matter properties based on gamma-ray flux observations.

Positron cooling and annihilation in galactic environments are consistent with observations.

Abstract

Many models of dark matter contain more than one new particle beyond those in the Standard Model. Often heavier particles decay into the lightest dark matter particle as the Universe evolves. Here we explore the possibilities that arise if one of the products in a (Heavy Particle) $\rightarrow$ (Dark Matter) decay is a positron, and the lifetime is shorter than the age of the Universe. The positrons cool down by scattering off the cosmic microwave background and eventually annihilate when they fall into Galactic potential wells. The resulting 511 keV flux not only places constraints on this class of models but might even be consistent with that observed by the INTEGRAL satellite.