Discriminating the source of high-energy positrons with AMS-02

TL;DR

This paper evaluates AMS-02's ability to distinguish between dark matter and pulsar origins of high-energy positron excess, finding that current data and catalogs are insufficient for definitive discrimination.

Contribution

It demonstrates that pulsar and dark matter explanations can mimic each other in AMS-02 data, highlighting the need for additional information for source identification.

Findings

Pulsars can mimic dark matter signals in AMS-02 data.

Current pulsar catalogs are incomplete, complicating source discrimination.

Discrimination requires better source knowledge or additional data.

Abstract

We study the prospects for discriminating between the dark matter (DM) and pulsar origin of the PAMELA positron excess with the Alpha Magnetic Spectrometer AMS-02. We simulate the response of AMS-02 to positrons (and electrons) originating from DM annihilations, and determine the pulsar parameters (spin-down luminosity, distance and characteristic age) that produce a satisfactory fit to the mock AMS-02 data. It turns out that it is always possible to mimic a DM signal with pulsars. Although the fit in some cases requires values of spin-down luminosity and characteristic age different from those of known pulsars in the ATNF and Fermi-LAT catalogues, these catalogues are known to be incomplete, and therefore the pulsar interpretation can hardly be ruled out. We also show that if the positron excess is due to a single pulsar, it is always possible to find a DM candidate that provides a good fit to the mock AMS-02 data. The discrimination between the two scenarios will thus require a better knowledge of the underlying sources, or complementary data.