Observation of the Identical Rigidity Dependence of He, C, and O Cosmic Rays at High Rigidities by the Alpha Magnetic Spectrometer on the International Space Station

Abstract

We report the observation of new properties of primary cosmic rays He, C, and O measured in the rigidity (momentum/charge) range 2 GV to 3 TV with $90 \times 10^6$ helium, $8.4 \times 10^6$ carbon, and $7.0 \times 10^6$ oxygen nuclei collected by the Alpha Magnetic Spectrometer (AMS) during the first five years of operation. Above 60 GV, these three spectra have identical rigidity dependence. They all deviate from a single power law above 200 GV and harden in an identical way.

Supplemental Material
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The helium, carbon and oxygen fluxes as a functions of rigidity at the top of AMS including errors due to statistics (stat); contributions to the systematic error from the trigger, acceptance, and background (acc); the rigidity resolution function and unfolding (unf); the absolute rigidity scale (scale); and the total systematic error (syst). The contribution of individual sources to the systematic error are added in quadrature to arrive at the total systematic error. The Monte Carlo event samples have sufficient statistics such that they do not contribute to the errors.
 

The helium to oxygen flux ratio He/O as a function of rigidity including errors due to statistics (stat); contributions to the systematic error from the trigger, acceptance, and background (acc); the rigidity resolution function and unfolding (unf); the absolute rigidity scale (scale); and the total systematic error (syst). The statistical errors are the sum in quadrature of the relative statistical errors of the helium and oxygen fluxes multiplied by the He/O ratio. The systematic errors from the background subtraction, the trigger, and the event reconstruction and selection are likewise added in quadrature. The correlations in the systematic errors from the uncertainty in nuclear interaction cross sections, the unfolding and the absolute rigidity scale between the helium and oxygen fluxes have been taken into account in calculating the corresponding systematic errors of the He/O ratio. The contribution of individual sources to the systematic error are added in quadrature to arrive at the total systematic uncertainty.
 

The carbon to oxygen flux ratio C/O as a function of rigidity including errors due to statistics (stat); contributions to the systematic error from the trigger, acceptance, and background (acc); the rigidity resolution function and unfolding (unf); the absolute rigidity scale (scale); and the total systematic error (syst). The statistical errors are the sum in quadrature of the relative statistical errors of the carbon and oxygen fluxes multiplied by the C/O ratio. The systematic errors from the background subtraction, the trigger, and the event reconstruction and selection are likewise added in quadrature. The correlations in the systematic errors from the uncertainty in nuclear interaction cross sections, the unfolding and the absolute rigidity scale between the carbon and oxygen fluxes have been taken into account in calculating the corresponding systematic errors of the C/O ratio. The contribution of individual sources to the systematic error are added in quadrature to arrive at the total systematic uncertainty.
 

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