The cosmic-ray positron energy spectrum measured by PAMELA

TL;DR

The PAMELA satellite measured the cosmic-ray positron spectrum up to 300 GeV, revealing results that challenge existing models and suggest additional sources of positrons in our Galaxy.

Contribution

This study provides the most extended and precise measurement of the cosmic-ray positron spectrum to date, offering new constraints on cosmic ray propagation and source models.

Findings

Positron flux measured up to 300 GeV

Results suggest additional astrophysical or exotic sources

Approximately 24,500 positrons observed during the period

Abstract

Precision measurements of the positron component in the cosmic radiation provide important information about the propagation of cosmic rays and the nature of particle sources in our Galaxy. The satellite-borne experiment PAMELA has been used to make a new measurement of the cosmic-ray positron flux and fraction that extends previously published measurements up to 300 GeV in kinetic energy. The combined measurements of the cosmic-ray positron energy spectrum and fraction provide a unique tool to constrain interpretation models. During the recent solar minimum activity period from July 2006 to December 2009 approximately 24500 positrons were observed. The results cannot be easily reconciled with purely secondary production and additional sources of either astrophysical or exotic origin may be required.