Observation of New Properties of Secondary Cosmic Rays Lithium, Beryllium, and Boron by the Alpha Magnetic Spectrometer on the International Space Station

Abstract

We report on the observation of new properties of secondary cosmic rays Li, Be, and B measured in the rigidity (momentum per unit charge) range 1.9 GV to 3.3 TV with a total of $5.4 \times 10^6$ nuclei collected by AMS during the first five years of operation aboard the International Space Station. The Li and B fluxes have an identical rigidity dependence above 7 GV and all three fluxes have an identical rigidity dependence above 30 GV with the Li/Be flux ratio of $2.0 \pm 0.1$. The three fluxes deviate from a single power law above 200 GV in an identical way. This behavior of secondary cosmic rays has also been observed in the AMS measurement of primary cosmic rays He, C, and O but the rigidity dependences of primary cosmic rays and of secondary cosmic rays are distinctly different. In particular, above 200 GV, the secondary cosmic rays harden more than the primary cosmic rays

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The lithium, beryllium and boron fluxes as 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 contamination (acc); the rigidity resolution function and unfolding (unf); the absolute rigidity scale (scale); and the total systematic error (syst). The contributions of individual sources to the systematic error are added in quadrature to arrive at the total systematic errors.
 

The Li/C, Be/C, B/C flux ratios as functions of rigidity including errors due to statistics (stat); contributions to the systematic error from the trigger, acceptance and background contamination (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 fluxes multiplied by the 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, unfolding, and the absolute rigidity scale between the fluxes have been accounted for in calculating the corresponding systematic errors. The contributions of individual sources to the systematic error are added in quadrature to arrive at the total systematic uncertainties.
 

The Li/O, Be/O and B/O flux ratios as functions of rigidity including errors due to statistics (stat); contributions to the systematic error from the trigger, acceptance and background contamination (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 fluxes multiplied by the 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, unfolding, and the absolute rigidity scale between the fluxes have been accounted for in calculating the corresponding systematic errors. The contributions of individual sources to the systematic error are added in quadrature to arrive at the total systematic uncertainties.
 

The Li/B and Be/B flux ratios as functions of rigidity including errors due to statistics (stat); contributions to the systematic error from the trigger, acceptance and background contamination (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 fluxes multiplied by the 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, unfolding, and the absolute rigidity scale between the fluxes have been accounted for in calculating the corresponding systematic errors. The contributions of individual sources to the systematic error are added in quadrature to arrive at the total systematic uncertainties.
 

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