Antiprotons from dark matter annihilation through light mediators and a possible excess in AMS-02 $\bar{p}/p$ data

TL;DR

This paper investigates how dark matter annihilation via light mediators can produce distinctive antiproton spectra, potentially explaining the AMS-02 observed excess and offering testable predictions to distinguish from other models.

Contribution

It introduces a light mediator dark matter scenario that better fits AMS-02 antiproton data and provides clear observational signatures to differentiate from alternative explanations.

Findings

Light mediators produce narrow antiproton spectra near the production threshold.

The scenario explains the AMS-02 excess better than direct annihilation or SNR models.

Predicted antiproton/proton ratio drops above 450 GeV, distinguishing it from other scenarios.

Abstract

We show that in the scenario where dark matter (DM) particles annihilate through light mediators, the energy spectra of the final state cosmic-ray particles depend strongly on the mediator mass. For final state antiprotons, a spectrum with relatively narrow peak occurs when the mediator mass is comparable to the $\pbar p$ production threshold. Of interest, the latest AMS-02 data on the $\pbar/p$ flux ratio hint at a bump-like excess over the expected background in the energy range $\sim100-450$ GeV. We show that such a light mediator scenario is favoured by the latest AMS-02 data over the scenarios of DM direct annihilation into the standard model particles and that of antiprotons produced from inside supernova remnants (SNRs), and is consistent with the upper limits derived from the Fermi-LAT data on the gamma rays towards the dwarf spheroidal galaxies. The $\pbar/p$ flux ratio with energy above 450 GeV is predicted to fall with energy quickly, which can be easily distinguished from the other two scenarios as they predict the ratio to be flattening or rising up to multi-TeV region.