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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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.

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Journal

Journal ID (iso-abbrev): Phys. Rev. Lett.

Title: Physical review letters

Publisher: American Physical Society (APS)

ISSN (Electronic): 1079-7114

ISSN (Print): 0031-9007

Publication date (Electronic): Nov 20 2015

Volume: 115

Issue: 21

Affiliations

[1 ] Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas (CIEMAT), E-28040 Madrid, Spain.

[2 ] INFN Sezione di Perugia, I-06100 Perugia, Italy.

[3 ] Università di Perugia, I-06100 Perugia, Italy.

[4 ] Institut für Experimentelle Kernphysik, Karlsruhe Institute of Technology (KIT), D-76128 Karlsruhe, Germany.

[5 ] Laboratório de Instrumentação e Física Experimental de Partículas (LIP), P-1000 Lisboa, Portugal.

[6 ] Jülich Supercomputing Centre and JARA-FAME, Research Centre Jülich, D-52425 Jülich, Germany.

[7 ] DPNC, Université de Genève, CH-1211 Genève 4, Switzerland.

[8 ] I. Physics Institute and JARA-FAME, RWTH Aachen University, D-52056 Aachen, Germany.

[9 ] Laboratoire de Physique Subatomique et de Cosmologie (LPSC), CNRS/IN2P3 and Université Grenoble-Alpes, F-38026 Grenoble, France.

[10 ] European Organization for Nuclear Research (CERN), CH-1211 Geneva 23, Switzerland.

[11 ] INFN Sezione di Roma 1, I-00185 Roma, Italy.

[12 ] INFN TIFPA, I-38123 Povo, Trento, Italy.

[13 ] Space Research Laboratory, Department of Physics and Astronomy, University of Turku, FI-20014 Turku, Finland.

[14 ] Università di Trento, I-38123 Povo, Trento, Italy.

[15 ] Massachusetts Institute of Technology (MIT), Cambridge, Massachusetts 02139, USA.

[16 ] Physics and Astronomy Department, University of Hawaii, Honolulu, Hawaii 96822, USA.

[17 ] INFN Sezione di Milano-Bicocca, I-20126 Milano, Italy.

[18 ] Università di Milano-Bicocca, I-20126 Milano, Italy.

[19 ] National Aeronautics and Space Administration Johnson Space Center (JSC), and Jacobs-Sverdrup, Houston, Texas 77058, USA.

[20 ] Università di Roma La Sapienza, I-00185 Roma, Italy.

[21 ] Laboratoire d'Annecy-le-Vieux de Physique des Particules (LAPP), CNRS/IN2P3 and Université de Savoie Mont Blanc, F-74941 Annecy-le-Vieux, France.

[22 ] CNR-IROE, I-50125 Firenze, Italy.

[23 ] INFN Sezione di Pisa, I-56100 Pisa, Italy.

[24 ] Department of Physics, Ewha Womans University, Seoul 120-750, Korea.

[25 ] National Central University (NCU), Chung-Li, Tao Yuan 32054, Taiwan.

[26 ] Institute of High Energy Physics (IHEP), Chinese Academy of Sciences, Beijing 100039, China.

[27 ] Shandong University (SDU), Jinan, Shandong 250100, China.

[28 ] Instituto de Astrofísica de Canarias (IAC), E-38205 La Laguna, and Departamento de Astrofísica, Universidad de La Laguna, E-38206 La Laguna, Tenerife, Spain.

[29 ] INFN Sezione di Bologna, I-40126 Bologna, Italy.

[30 ] Università di Bologna, I-40126 Bologna, Italy.

[31 ] Institute of Electrical Engineering (IEE), Chinese Academy of Sciences, Beijing 100190, China.

[32 ] Department of Physics, Middle East Technical University (METU), 06800 Ankara, Turkey.

[33 ] Institute of Physics, Academia Sinica, Nankang, Taipei 11529, Taiwan.

[34 ] Physics Department, Yale University, New Haven, Connecticut 06520, USA.

[35 ] Southeast University (SEU), Nanjing 210096, China.

[36 ] Instituto de Física, Universidad Nacional Autónoma de México (UNAM), México, D. F. 01000 Mexico.

[37 ] Università di Pisa, I-56100 Pisa, Italy.

[38 ] Sun Yat-Sen University (SYSU), Guangzhou 510275, China.

[39 ] National Chung-Shan Institute of Science and Technology (NCSIST), Longtan, Tao Yuan 325, Taiwan.

[40 ] CHEP, Kyungpook National University, 702-701 Daegu, Korea.

[41 ] Academia Sinica Grid Center (ASGC), Nankang, Taipei 11529, Taiwan.

[42 ] Beihang University (BUAA), Beijing 100191, China.

[43 ] IPST, University of Maryland, College Park, Maryland 20742, USA.

[44 ] East-West Center for Space Science, University of Maryland, College Park, Maryland 20742, USA.

[45 ] Shanghai Jiaotong University (SJTU), Shanghai 200030, China.

[46 ] Instituto de Fìsica de São Carlos, Universidade de São Paulo, CP 369, 13560-970 São Carlos, São Paulo, Brazil.

[47 ] National Cheng Kung University, Tainan 701, Taiwan.

Article

DOI: 10.1103/PhysRevLett.115.211101

PubMed ID: 26636836

SO-VID: cc625d57-12ac-4da4-a34c-1011d1a24fa7

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