A Measurement of Cosmic Ray Electron and Positron Fluxes above 4.5 GEV.

Measurements have been made of electron and positron cosmic ray fluxes above 4.5 GeV using a balloon-borne superconducting -magnet spectrometer. The instrument uses a gas Cerenkov detector, a shower counter and scintillators in conjunction with the spectrometer to separate the cosmic ray species. Observations of approximately 2200 electrons and 140 positrons are used to determine that the electron differential flux is 445 E('-(3.25 (+OR-) .20)) (m('2)-str-s-GeV)('-1) to an accuracy of 10% and, assuming a spectral index of 2.75, the positron flux is 13 E('-2.75) (m('2)-str-s-GeV)('-1) to an accuracy of 25%. E is the total energy in GeV.