Precision Measurement of the Helium Flux in Primary Cosmic Rays of Rigidities 1.9 GV to 3 TV with the Alpha Magnetic Spectrometer on the International Space Station
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PhysRevLett.115.211101.pdf
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Author(s)
Aguilar, M.
Aisa, D.
Alpat, B.
Alvino, A.
Ambrosi, G.
Andeen, K.
Arruda, L.
Attig, N.
Azzarello, P.
Bachlechner, A.
Date Issued
November 2015
Journal
Physical Review Letters
Publisher
American Physical Society
Citation
Aguilar, M., et al. "Precision Measurement of the Helium Flux in Primary Cosmic Rays of Rigidities 1.9 GV to 3 TV with the Alpha Magnetic Spectrometer on the International Space Station." Phys. Rev. Lett. 115, 211101 (November 2015).
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Final published version
Abstract
Knowledge of the precise rigidity dependence of the helium flux is important in understanding the origin, acceleration, and propagation of cosmic rays. A precise measurement of the helium flux in primary cosmic rays with rigidity (momentum/charge) from 1.9 GV to 3 TV based on 50 million events is presented and compared to the proton flux. The detailed variation with rigidity of the helium flux spectral index is presented for the first time. The spectral index progressively hardens at rigidities larger than 100 GV. The rigidity dependence of the helium flux spectral index is similar to that of the proton spectral index though the magnitudes are different. Remarkably, the spectral index of the proton to helium flux ratio increases with rigidity up to 45 GV and then becomes constant; the flux ratio above 45 GV is well described by a single power law.
MIT Department
Massachusetts Institute of Technology. Department of Physics
Massachusetts Institute of Technology. Laboratory for Nuclear Science
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DOI of Published Version
https://doi.org/10.1103/PhysRevLett.115.211101
