The cosmic ray positron to electron ratio in the energy range 0.85 to 14 GeV

We report on the positron to electron ratio in the cosmic radiation over more than one decade in energy from 0.85 to 14GeV, using the NMSU-WiZard/CAPRICE balloon borne magnet spectrometer. The spectrometer uses a solid radiator RICH detector and a silicon-tungsten calorimeter for particle identification. The proton rejection factor of the two instruments combined is better than 2x10^-6^ between 0.6 and 3GV/c dropping to 6x10^-5^ at 5GV/c and 10^-^4 at 10GV/c. The data was collected during 23 hours at a mean residual atmosphere of 4.0g/cm2. From a total of 2756 well identifiede^-^ and 498e^+^ we are able to construct the positron fraction R=e^+^/(e^+^+e^-^) as a function of energy with small errors from 0.85GeV to 14GeV for the first time. We observe a decreasing ratio in this energy region. This energy dependent behaviour is consistent with the simple leaky box model. The positron fraction in the upper energy bins are in agreement with the latest high energy measurements.