Abstract.A measurement of the energy spectra of cosmic-ray positrons and electrons was made with a balloon-borne magnetspectrometer, which was flown at a mean geomagnetic cut-off of 4.5 GV/c. The observed positron flux in the energy range 7-16 GeV is approximately an order of magnitude lower than that of electrons, as measured in other experiments at various energies. The power law spectral index of the observed differential energy spectrum of electrons is −2.89 ± 0.10 in the energy interval 7.5-47 GeV. For positrons the overall fit of the available data above 7 GeV has been considered. The spectral index is found to be −3.37 ± 0.26 and the fraction of positrons, e + /(e + + e − ), has a mean value of 0.064 ± 0.003. The world data on e + /(e + + e − ) from 0.1 to 30 GeV indicate that a plerion type electron spectrum is preferred over the other types. The trend of the presently existing high energy data also suggests a possible contribution of positrons produced at the pulsar polar cap. High resolution experiments capable of identifying positrons at least up to 100 GeV with high statistics are required to pinpoint the origin of both electrons and positrons in the cosmic radiation.

The antiproton-to-proton ratio, p/p, in cosmic rays has been measured in the energy range 3.7-19 GeV. This measurement was carried out using a balloon-borne superconducting magnetic spectrometer along with a gas Cerenkov counter, an imaging calorimeter, and a time-of-flight scintillator system. The measured p/p ratio was determined to be 1.24 Ϫ0.51 ϩ0.68 ϫ 10 Ϫ4. The present result, along with other recent observations, shows that the observed abundances of antiprotons are consistent with models in which antiprotons are produced as secondaries during the propagation of cosmic rays in the Galaxy.

We calculate the p background in the upper atmosphere which results when primary cosmic rays interact with air nuclei. Since the p yield from p-nucleus and nucleus-nucleus interactions is not directly known from experiments, we derive these quantities by using a Monte Carlo simulation which is theoretically based on the dual parton model and which had been successfully applied to the description of hadron production in high energy collisions. Results on the calculated atmospheric p background indicate a larger p background than earlier estimates predicted, particularly at low energies.

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