Observation of an anomalous positron abundance in the cosmic radiation

TL;DR

This paper reports an unexpected excess of high-energy positrons in cosmic radiation, which could indicate dark matter annihilations or pulsar sources, with solar activity influencing low-energy positron levels.

Contribution

It provides the first high-energy positron measurements from PAMELA, revealing deviations from secondary production models and suggesting potential dark matter or pulsar origins.

Findings

High-energy positron excess observed between 1.5-100 GeV

Deviation from secondary production model predictions

Solar activity impacts low-energy positron abundance

Abstract

Positrons are known to be produced in interactions between cosmic-ray nuclei and interstellar matter ("secondary production"). Positrons may, however, also be created by dark matter particle annihilations in the galactic halo or in the magnetospheres of near-by pulsars. The nature of dark matter is one of the most prominent open questions in science today. An observation of positrons from pulsars would open a new observation window on these sources. Here we present results from the PAMELA satellite experiment on the positron abundance in the cosmic radiation for the energy range 1.5 - 100 GeV. Our high energy data deviate significantly from predictions of secondary production models, and may constitute the first indirect evidence of dark matter particle annihilations, or the first observation of positron production from near-by pulsars. We also present evidence that solar activity significantly affects the abundance of positrons at low energies.