Measurement of the Cosmic-Ray Antiproton to Proton Abundance Ratio between 4 and 50 GeV
A. S. Beach, J. J. Beatty, A. Bhattacharyya, C. Bower, S. Coutu, M. A. DuVernois, A. W. Labrador, S. McKee, S. A. Minnick, D. Muller, J. Musser, S. Nutter, M. Schubnell, S. Swordy, G. Tarle, A. Tomasch
Abstract
We present a new measurement of the antiproton to proton abundance ratio, pbar/p, in the cosmic radiation. The HEAT-pbar instrument, a balloon borne magnet spectrometer with precise rigidity and multiple energy loss measurement capability, was flown successfully in Spring 2000, at an average atmospheric depth of 7.2 g/cm2. A total of 71 antiprotons were identified above the vertical geomagnetic cut-off rigidity of 4.2 GV. The highest measured proton energy was 81 GeV. We find that the pbar/p abundance ratio agrees with that expected from a purely secondary origin of antiprotons produced by primary protons with a standard soft energy spectrum.
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