Is There a Dark Matter Signal in the Galactic Positron Annihilation Radiation?

TL;DR

This paper argues that the observed galactic positron annihilation radiation can be explained by standard nucleosynthetic sources if positron propagation is considered, challenging previous claims of dark matter signals.

Contribution

It demonstrates that positron propagation effects allow standard sources to explain the observed annihilation features, reducing the need for dark matter explanations.

Findings

Dark matter cannot explain the positronium fraction without extensive propagation.

Standard nucleosynthetic sources can account for spatial distribution and positronium fraction.

Propagation effects are crucial in interpreting galactic positron annihilation data.

Abstract

Assuming Galactic positrons do not go far before annhilating, a difference between the observed 511 keV annihilation flux distribution and that of positron production, expected from beta-plus decay in Galactic iron nucleosynthesis, was evoked as evidence of a new source and a signal of dark matter. We show, however, that the dark mater sources can not account for the observed positronium fraction without extensive propagation. Yet with such propagation, standard nucleosynthetic sources can fully account for the spatial differences and the positronium fraction, leaving no signal for dark mater to explain.