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

Phys. Rev. Lett. 117, 091103 (2016)
Published on:
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 $3.49 \times 10^5$ antiproton events and $2.42 \times 10^9$ 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 $ \bar{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 ($\bar{p}/p$), ($\bar{p}/e^-$), and ($p/e^{+}$) flux ratios each reaches a maximum. From ~60 to ~500 GV, the ($\bar{p}/p $), ($\bar{p}/e^+ $), and ($\bar{p}/e^+ $) flux ratios show no rigidity dependence. These are new observations of the properties of elementary particles in the cosmos.

 

Supplemental Material
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Table-SM-I

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The antiproton flux $\Phi^{\bar p}$ and the antiproton/proton flux ratio $\Phi^{\bar p}/\Phi^{p}$ as a function of absolute rigidity at the top of AMS. $\tilde{N}^{\bar p}$ is the number of antiprotons observed in each rigidity bin rounded to the nearest integer. $\sigma_{\rm stat}$ and $\sigma_{\rm syst}$ are the respective statistical and systematic errors.

Table-SM-II

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The antiproton-to-positron flux ratio $\Phi^{\bar p}/\Phi^{e^+}$ and the antiproton-to-electron flux ratio $\Phi^{\bar p}/\Phi^{e^-}$ as a function of rigidity at the top of AMS. $\sigma_{\rm stat}$ are the statistical errors on the ratios, $\sigma_{\rm syst}$ are the systematic errors on the ratios, and $\sigma_{\rm scale}$ are the errors from the energy scale uncertainty in $\Phi^{e^\pm}$. The antiproton flux binning is used.

Table-SM-III

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The proton-to-positron flux ratio $\Phi^{p}/\Phi^{e^+}$ and the proton-to-electron flux ratio $\Phi^{p}/\Phi^{e^-}$ as a function of rigidity at the top of AMS. $\sigma_{\rm stat}$ are the statistical errors on the ratios, $\sigma_{\rm syst}$ are the systematic errors on the ratios, and $\sigma_{\rm scale}$ are the errors from the energy scale uncertainty in $\Phi^{e^\pm}$. The proton flux binning is used.

External Databases
AMS Data at CRDB (Cosmic-ray DataBase)

The CRDB at LPSC/IN2P3/CNRS, online since 2013, is fully described in Maurin et al. (2014, 2020)

AMS Data at Cosmic Ray DataBase (CRDB) © SSDC

The CRDB © SSDC is developed at the Space Science Data Center, a facility of the Italian Space Agency (ASI).