@article{5701de9cd65d4517b0c39f4e5f899ff5,
title = "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",
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.",
author = "{AMS Collaboration} and M. Aguilar and D. Aisa and B. Alpat and A. Alvino and G. Ambrosi and K. Andeen and L. Arruda and N. Attig and P. Azzarello and A. Bachlechner and F. Barao and A. Barrau and L. Barrin and A. Bartoloni and L. Basara and M. Battarbee and R. Battiston and J. Bazo and U. Becker and M. Behlmann and B. Beischer and J. Berdugo and B. Bertucci and V. Bindi and S. Bizzaglia and M. Bizzarri and G. Boella and {De Boer}, W. and K. Bollweg and V. Bonnivard and B. Borgia and S. Borsini and Boschini, {M. J.} and M. Bourquin and J. Burger and F. Cadoux and Cai, {X. D.} and M. Capell and S. Caroff and J. Casaus and G. Castellini and I. Cernuda and D. Cerreta and F. Cervelli and Chae, {M. J.} and Chang, {Y. H.} and Chen, {A. I.} and Chen, {G. M.} and H. Chen and Chen, {H. S.} and Liqiu Wang",
note = "Publisher Copyright: {\textcopyright} 2015 authors. Published by the American Physical Society. Published by the American Physical Society under the terms of the «http://creativecommons.org/licenses/by/3.0/» Creative Commons Attribution 3.0 License. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.",
year = "2015",
month = nov,
day = "17",
doi = "10.1103/PhysRevLett.115.211101",
language = "English",
volume = "115",
journal = "Physical Review Letters",
issn = "0031-9007",
publisher = "American Physical Society",
number = "21",
}