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 0⁵ antiproton events and 2.42 ×1 0⁹ 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⁺ fluxes are found to have nearly identical rigidity dependence and the electron e^- flux exhibits a different rigidity dependence. Below 60 GV, the (p ¯/p ), (p ¯/e⁺), and (p /e⁺) flux ratios each reaches a maximum. From ∼60 to ∼500 GV , the (p ¯/p ), (p ¯/e⁺), and (p /e⁺) flux ratios show no rigidity dependence. These are new observations of the properties of elementary particles in the cosmos.