Precision measurement of cosmic-ray antiproton spectrum

The energy spectrum of cosmic-ray antiprotons (p^¯′s) has been measured in the range 0.18−3.56 GeV, based on 458 (p^¯′s) collected by BESS in a recent solar-minimum period. We have detected for the first time a characteristic peak at 2 GeV of (p^¯′s) originating from cosmic-ray interactions with the interstellar gas. The peak spectrum is reproduced by theoretical calculations, implying that the propagation models are basically correct and that different cosmic-ray species undergo a universal propagation. Future BESS data with still higher statistics will allow us to study the solar modulation and the propagation in detail and to search for primary p^¯ components.