Recent Cosmic-Ray Antiproton Measurements and Astrophysical Implications

Cosmic-ray antiprotons have been detected by a new balloon-borne experiment which covers the energy range between 130 and 320 MeV. Fourteen detected events yield a measured flux of 1.7±0.5 x 10^(-4) antiprotons m^(-2) sr^(-1) s(-1) MeV^(-1). The corresponding antiproton/proton ratio is 2.2± 0.6 x 10^(-4), only slightly smaller than the ratio observed by other experiments at higher energies. The measured flux is significantly larger than predicted, and some cosmic-ray models which could explain this result are discussed.