12-20 July 2017
Asia/Seoul timezone
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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


  • Weiwei XU

Primary authors

  • Weiwei XU (Massachusetts Institute of Technology, United States)


  • Zuhao LI (Institute of High Energy Physics, CAS, China)


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.