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VERSION:2.0
CALSCALE:GREGORIAN
PRODID:UW-Madison-Physics-Events
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SEQUENCE:0
UID:UW-Physics-Event-2598
DTSTART:20120305T170000Z
DURATION:PT1H0M0S
DTSTAMP:20260414T122702Z
LAST-MODIFIED:20120215T231720Z
LOCATION:5280 Chamberlin Hall
SUMMARY:Antiparticles in the shadow of the Earth: cosmic-ray positrons
  with the Fermi Gamma-ray Space Telescope\, NPAC (Nuclear/Particle/Ast
 ro/Cosmo) Forum\, Justin Vandenbroucke\, SLAC
DESCRIPTION:Cosmic rays are primarily protons and other nuclei\, but t
 here is a small flux of electrons and an even smaller flux of positron
 s.  Cosmic-ray positrons can be produced by astrophysical accelerators
 \, by collisions of cosmic-ray protons with interstellar gas\, or by d
 ark matter.  We used the Fermi Gamma-ray Space Telescope to measure th
 e charge-separated electron and positron energy spectra.  Because Ferm
 i does not have an onboard magnet\, we used the Earth's magnetic field
  to distinguish positrons and electrons.  We confirmed the PAMELA disc
 overy that the positron fraction is rising with energy between 10 and 
 100 GeV and measured the positron flux for the first time in the 100-2
 00 GeV range.  Explaining the positron excess remains an outstanding q
 uestion.
URL:https://www.physics.wisc.edu/events/?id=2598
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