Observation of cosmic ray positrons in the region from 5 to 50 GeV

The absolute flux of cosmic ray positrons has been measured using a balloon-borne magnet-spectrometer. Based on 193 positrons observed from 3.57 GV/c to 50 GV/c rigidity at the payload, the integral flux about 5 GeV kinetic energy at the top of the atmosphere is found to be (0.33±0.07)e⁺/m²-str-s. At the top of the atmosphere the effective energy interval for the observation is 4.5 to 64 GeV. In this interval the best-fit differential flux is 16E^-(3.0±0.3)e⁺/(m²-str-sec-GeV). The quoted errors do not include a possible 10% systematic uncertainty in the exposure factor. The ratio e⁺/(e⁺+e^-) was found to be 0.069±0.014 above 5 GeV. The authors compare these results with other observations and theoretical predictions.