New Limit on the Low-Energy Antiproton/Proton Ratio in the Galactic Cosmic Radiation

Abstract
We describe the results of a balloon-borne apparatus searching for low-energy antiprotons in the Galactic cosmic rays. For energies less than 640 MeV at the top of the atmosphere, no cosmic-ray antiprotons were observed. This yields an upper limit to the p¯p ratio of 4.6×105 at the 85% confidence level.