BEXCO - Room A(101/102)
[CRD059] Antiproton Flux and Antiproton-to-Proton Flux Ratio in Primary Cosmic Rays Measured with the AMS Detector on ISS
Precision measurements by AMS of the antiproton flux and the antiproton-to-proton flux ratio in primary cosmic rays in the absolute rigidity range from 1 to 450 GV are presented based on 3.49 x 10^5 antiproton events and 2.42 x 10^9 proton events. At ~20 GV the antiproton-to-proton flux ratio reaches a maximum. Unexpectedly, above 60 GV the antiproton spectral index is consistent with the proton spectral index and the antiproton-to-proton flux ratio shows no rigidity dependence in the rigidity range from ~60 to ~500 GV. This unexpected observation requires new explanation of the origin of cosmic ray antiprotons.