Measurement of Cosmic-Ray Antiprotons from 3.7 to 19 GeV

The antiproton-to-proton ratio, / p , in cosmic rays has been measured in the energy range 3.7-19 GeV. This measurement was carried out using a balloon-borne superconducting magnetic spectrometer along with a gas Cerenkov counter, an imaging calorimeter, and a time-of-flight scintillator system. The measured / p ratio was determined to be 1.24 −0.51 +0.68 × 10 -4 . The present result, along with other recent observations, shows that the observed abundances of antiprotons are consistent with models in which antiprotons are produced as secondaries during the propagation of cosmic rays in the Galaxy.