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Cosmic-ray positron energy spectrum measured by PAMELA
O Adriani1, G C Barbarino, G A Bazilevskaya
1Department of Physics, University of Florence, I-50019 Sesto Fiorentino, Florence, Italy and INFN, Sezione di Florence, I-50019 Sesto Fiorentino, Florence, Italy.
Physical Review Letters
|September 10, 2013
Summary
The PAMELA satellite measured cosmic ray positrons up to 300 GeV. Results suggest these positrons may originate from exotic sources, not just secondary production.
Area of Science:
- Cosmic ray physics
- Particle astrophysics
- Galactic cosmic ray studies
Background:
- Precision measurements of cosmic ray positrons offer insights into galactic cosmic ray propagation and source characteristics.
- The Payload for Antimatter-Matter Exploration and Light-nuclei Apportionment (PAMELA) experiment is a key instrument for studying cosmic ray composition.
Purpose of the Study:
- To present new measurements of the cosmic-ray positron flux and fraction up to 300 GeV kinetic energy.
- To constrain models of cosmic ray propagation and origin by combining new data with previous findings.
Main Methods:
- Utilized data from the PAMELA satellite experiment, collected during the solar minimum period from July 2006 to December 2009.
- Observed approximately 24,500 positrons within the specified energy range.
Main Results:
- Extended previous measurements of the cosmic-ray positron flux and fraction to higher energies (up to 300 GeV).
- The observed positron spectrum and fraction deviate from predictions based solely on secondary production.
Conclusions:
- The experimental results are not fully explained by secondary production mechanisms alone.
- Additional positron sources, potentially of astrophysical or exotic (e.g., dark matter annihilation) origin, may be necessary to account for the observed data.
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