Cosmic-ray positron energy spectrum measured by PAMELA. Physical Review Letters Volume 111, Issue 8, 19 August 2013, Article number 081102

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 24 500 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.
Indexed keywords
Combined measurements; Interpretation model; Positron energy; Precision measurement; Satellite-borne experiment; Secondary production; Solar minima