AMS-02 Positron Excess and Indirect Detection of Three-body Decaying Dark Matter

TL;DR

This paper investigates three-body decaying dark matter models as a way to explain the AMS-02 positron excess, showing that certain decay channels can fit the data without conflicting with gamma-ray and anti-proton constraints.

Contribution

It introduces a detailed analysis of three-body dark matter decays, demonstrating their potential to explain positron excess while evading existing astrophysical constraints.

Findings

Decays into electron-positron pairs can explain the positron excess.

Decays into muon pairs or mixed flavors are viable under certain propagation models.

Decays into other fermions are strongly disfavored.

Abstract

We consider indirect detection of meta-stable dark matter particles decaying into a stable neutral particle and a pair of standard model fermions. Due to the softer energy spectra from the three-body decay, such models could potentially explain the AMS-02 positron excess without being constrained by the Fermi-LAT gamma-ray data and the cosmic ray anti-proton measurements. We scrutinize over different final state fermions, paying special attention to handling of the cosmic ray background and including various contributions from cosmic ray propagation with the help of the \textsc{LikeDM} package. It is found that primary decays into an electron-positron pair and a stable neutral particle could give rise to the AMS-02 positron excess and, at the same time, stay unscathed against the gamma-ray and anti-proton constraints. Decays to a muon pair or a mixed flavor electron-muon pair may also be viable depending on the propagation models. Decays to all other standard model fermions are severely disfavored.