skip to main content

DOE PAGESDOE PAGES

Title: Measurement of Separate Cosmic-Ray Electron and Positron Spectra with the Fermi Large Area Telescope

We measured separate cosmic-ray electron and positron spectra with the Fermi Large Area Telescope. Because the instrument does not have an onboard magnet, we distinguish the two species by exploiting the Earth’s shadow, which is offset in opposite directions for opposite charges due to the Earth’s magnetic field. We estimate and subtract the cosmic-ray proton background using two different methods that produce consistent results. We report the electron-only spectrum, the positron-only spectrum, and the positron fraction between 20 GeV and 200 GeV. We confirm that the fraction rises with energy in the 20–100 GeV range. The three new spectral points between 100 and 200 GeV are consistent with a fraction that is continuing to rise with energy.
Authors:
 [1]
  1. Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany); et al.
Publication Date:
Grant/Contract Number:
AC02-76SF00515
Type:
Accepted Manuscript
Journal Name:
Physical Review Letters
Additional Journal Information:
Journal Volume: 108; Journal Issue: 1; Journal ID: ISSN 0031-9007
Publisher:
American Physical Society (APS)
Research Org:
SLAC National Accelerator Lab., Menlo Park, CA (United States)
Sponsoring Org:
USDOE
Contributing Orgs:
Fermi LAT Collaboration
Country of Publication:
United States
Language:
English
Subject:
79 ASTRONOMY AND ASTROPHYSICS
OSTI Identifier:
1356772
Alternate Identifier(s):
OSTI ID: 1098536