Antiproton flux and antiproton-to-proton flux ratio measured with the alpha magnetic spectrometer on the ISS

AMS-02 is a multi-purpose particle detector for cosmic rays onboard the International Space Station. Due to the very small abundance of antiprotons in the cosmic radiation of about 10^-5 compared to protons a very precise particle identification is crucial. The methods to identify antiprotons in the cosmic-ray measurement of AMS-02 in different energy regions will be discussed. The precision measurement of the antiproton flux by AMS-02 and the antiproton-to-proton flux ratio in primary cosmic rays in the absolute rigidity range from 1 to 450 GeV based on 3.49 x 10⁵ antiproton events and 2.42 x 10⁹ proton events is presented. The antiproton-to-proton flux ratio reaches a maximum at approximately 20 GeV and is rigidity independent above 60.3 GeV.