Antiproton Flux, Antiproton-to-Proton Flux Ratio, and Properties of Elementary Particle Fluxes in Primary Cosmic Rays Measured with the Alpha Magnetic Spectrometer on the International Space Station

A precision measurement 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 is presented based on 3.49 1 0<SUP>5</SUP> antiproton events and 2.42 1 0<SUP>9</SUP> proton events. The fluxes and flux ratios of charged elementary particles in cosmic rays are also presented. In the absolute rigidity range ˜60 to ˜500 GV , the antiproton p , proton p , and positron e<SUP>+</SUP> fluxes are found to have nearly identical rigidity dependence and the electron e<SUP>-</SUP> flux exhibits a different rigidity dependence. Below 60 GV, the (p /p ), (p /e<SUP>+</SUP>), and (p /e<SUP>+</SUP>) flux ratios each reaches a maximum. From ˜60 to ˜500 GV , the (p /p ), (p /e<SUP>+</SUP>), and (p /e<SUP>+</SUP>) flux ratios show no rigidity dependence. These are new observations of the properties of elementary particles in the cosmos.