A search for cosmic-ray antiprotons was performed using a balloon-borne experiment with a superconducting magnetic rigidity spectrometer (BESS). We have detected four antiprotons in the kinetic energy range between 300 and 500 MeV, the first antiprotons to be identified by a direct mass measurement. The corresponding p»p flux ratio at the top of the atmosphere is found to be 1.2-0.65+1.0 × 10-5. No antiprotons were observed in the range between 175 and 300 MeV, resulting in a 90% C.L. upper limit on the flux ratio of 2.9 × 10-5.
ASJC Scopus subject areas
- Physics and Astronomy(all)