Measurement of the high energy cosmic ray electron spectrum with the Fermi large area telescope

The Large Area Telescope (LAT) onboard the Fermi satellite is composed by 16 identical tower modules, each consisting of a silicon strip tracker (TKR) interleaved with tungsten foils and followed by a CsI crystal hodoscopic calorimeter (CAL), surrounded by a segmented anticoincidence scintillator detector (ACD). Even though it was designed to be a high sensitivity gamma-ray telescope, the Fermi LAT has proved to be an excellent electron/positron detector. A dedicated analysis has been developed to reconstruct the primary cosmic ray electron/positron spectrum. Our result shows that in the energy range from 20 GeV up to 1 TeV the spectrum follows a simple power law with spectral index close to 3.0. In this paper the analysis procedure will be illustrated and the main results will be shown. © 2010 American Institute of Physics.