LIMITS ON THE ANTIPROTON PROTON RATIO IN THE COSMIC-RADIATION FROM 100 MEV TO 1580 MEV

A search for antiprotons (p̄'s) in the cosmic radiation with energies below 1580 MeV at the top of the atmosphere was performed using the PBAR balloon-borne magnetic spectrometer. No antiprotons were observed in 1.24 × 105 proton events. For the energy interval 100-640 MeV, we report an upper limit to the p̄/p ratio of 2.8 × 10-5 (85% C.L.) at the top of the atmosphere, after correcting for instrumental efficiencies and contributions from secondary particles. We also observed no antiproton in the energy interval 640-1580 MeV, which yields an upper limit to the p̄/p ratio of 6.1 × 10-5 (85% confidence level, (C.L.)). By combining both data sets, the limits on the p̄/p ratio can be improved to 2.0 × 10-5 (85% C.L.). We discuss the detector performance and instrumental efficiencies of the individual detector components. A detailed Monte Carlo calculation was used to evaluate the instrumental efficiency for both antiprotons and protons as a function of momentum. Finally we discuss the constraints that these data might place on a variety of p̄ production models.