Systematic study of the uncertainties in fitting the cosmic positron data by AMS-02

TL;DR

This paper systematically analyzes the uncertainties in theoretical models explaining AMS-02 cosmic positron data, highlighting how these uncertainties affect interpretations of potential sources like pulsars or dark matter.

Contribution

It provides a comprehensive assessment of model uncertainties impacting the interpretation of cosmic positron excesses in AMS-02 data.

Findings

Spectral hardening of primary electrons above 50-100 GeV is favored.

Model uncertainties can double the parameter space for dark matter explanations.

Systematic uncertainties significantly influence the inferred properties of cosmic positron sources.

Abstract

The operation of AMS-02 opens a new era for the study of cosmic ray physics with unprecedentedly precise data which are comparable with the laboratory measurements. The high precision data allow a quantitative study on the cosmic ray physics and give strict constraints on the nature of cosmic ray sources. However, the intrinsic errors from the theoretical models to interpret the data become dominant over the errors in the data. In the present work we try to give a systematic study on the uncertainties of the models to explain the AMS-02 positron fraction data, which shows the cosmic ray $e^+e^-$ excesses together with the PAMELA and Fermi-LAT measurements. The excesses can be attributed to contributions from the extra $e^+e^-$ sources, such as pulsars or the dark matter annihilation. The possible systematic uncertainties of the theoretical models considered include the cosmic ray propagation, the treatment of the low energy data, the solar modulation, the $pp$ interaction models, the nuclei injection spectrum and so on. We find that in general a spectral hardening of the primary electron injection spectrum above $\sim50-100$ GeV is favored by the data. Furthermore, the present model uncertainties may lead to a factor of $\sim2$ enlargement in the determination of the parameter regions of the extra source, such as the dark matter mass, annihilation rate and so on.