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

Abstract

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 $3.49\ifmmode\times\else\texttimes\fi{}1{0}^{5}$ antiproton events and $2.42\ifmmode\times\else\texttimes\fi{}1{0}^{9}$ proton events. The fluxes and flux ratios of charged elementary particles in cosmic rays are also presented. In the absolute rigidity range $\ensuremath{\sim}60$ to $\ensuremath{\sim}500\text{ }\text{ }\mathrm{GV}$, the antiproton $\overline{p}$, proton $p$, and positron ${e}^{+}$ fluxes are found to have nearly identical rigidity dependence and the electron ${e}^{\ensuremath{-}}$ flux exhibits a different rigidity dependence. Below 60 GV, the ($\overline{p}/p$), ($\overline{p}/{e}^{+}$), and ($p/{e}^{+}$) flux ratios each reaches a maximum. From $\ensuremath{\sim}60$ to $\ensuremath{\sim}500\text{ }\text{ }\mathrm{GV}$, the ($\overline{p}/p$), ($\overline{p}/{e}^{+}$), and ($p/{e}^{+}$) flux ratios show no rigidity dependence. These are new observations of the properties of elementary particles in the cosmos.