Measurement of the positron to electron ratio in the cosmic rays above 5 GeV

As part of a series of experiments to search for antimatter in cosmic rays, the NMSU balloon-borne magnet spectrometer was configured for a flight to study positrons. Two completely new instruments, a transition radiation detector and a silicon-tungsten imaging calorimeter, were added to the magnet spectrometer. These two detectors provided a proton rejection factor better than (3) (10)4. This instrument was flown from Fort Sumner, NM at an average depth of 4.5 g/cm2 of residual atmosphere for a period of 25 hours. The paper reports the measured fraction of positrons e+/e++e- from about 5 to 60 GeV at the top of the atmosphere. The measurements do not show any compelling evidence for an increase in this ratio with energy and the results are consistent with a constant fraction of 0.78±0.016 over the entire region