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Electron and Positron Fluxes in Primary Cosmic Rays Measured with the Alpha Magnetic Spectrometer on the International Space Station

M. Aguilar26, D. Aisa33,34, A. Alvino33, G. Ambrosi33, K. Andeen22, L. Arruda24, N. Attig21, P. Azzarello33,16,†, A. Bachlechner1 et al. (AMS Collaboration)

A. Bachlechner1, F. Barao24, A. Barrau17, L. Barrin15, A. Bartoloni38, L. Basara3,37, M. Battarbee44, R. Battiston37,‡, J. Bazo33, U. Becker9, M. Behlmann9, B. Beischer1, J. Berdugo26, B. Bertucci33,34, G. Bigongiari35,36, V. Bindi19, S. Bizzaglia33, M. Bizzarri33,34, G. Boella28,29, W. de Boer22, K. Bollweg20, V. Bonnivard17, B. Borgia38,39, S. Borsini33, M. J. Boschini28, M. Bourquin16, J. Burger9, F. Cadoux16, X. D. Cai9, M. Capell9, S. Caroff3, J. Casaus26, V. Cascioli33, G. Castellini14, I. Cernuda26, F. Cervelli35, M. J. Chae40, Y. H. Chang10, A. I. Chen9, H. Chen9, G. M. Cheng6, H. S. Chen6, L. Cheng41, A. Chikanian32,*, H. Y. Chou10, E. Choumilov9, V. Choutko9, C. H. Chung1, C. Clark20, R. Clavero23, G. Coignet3, C. Consolandi19, A. Contin7,8, C. Corti19, B. Coste37, Z. Cui41, M. Dai5, C. Delgado26, S. Della Torre28, M. B. Demirköz2, L. Derome17, S. Di Falco35, L. Di Masso33,34, F. Dimiccoli37, C. Díaz26, P. von Doetinchem19, W. J. Du41, M. Duranti33, D. D’Urso33, A. Eline9, F. J. Eppling9, T. Eronen44, Y. Y. Fan43,§, L. Farnesini33, J. Feng3,∥, E. Fiandrini33,34, A. Fiasson3, E. Finch32, P. Fisher9, Y. Galaktionov9, G. Gallucci35,15, B. García26, R. García-López23, H. Gast1, I. Gebauer22, M. Gervasi28,29, A. Ghelfi17, W. Gillard10, F. Giovacchini26, P. Goglov9, J. Gong31, C. Goy3, V. Grabski27, D. Grandi28, M. Graziani33,15, C. Guandalini7,8, I. Guerri35,36, K. H. Guo18, M. Habiby16, S. Haino10,43, K. C. Han25, Z. H. He18, M. Heil22,9, J. Hoffman10, T. H. Hsieh9, Z. C. Huang18, C. Huh13, M. Incagli35, M. Ionica33, W. Y. Jang13, H. Jinchi25, K. Kanishev37, G. N. Kim13, K. S. Kim13, Th. Kirn1, R. Kossakowski3, O. Kounina9, A. Kounine9, V. Koutsenko9, M. S. Krafczyk9, S. Kunz22, G. La Vacca28,15, E. Laudi33,34,¶, G. Laurenti7,8, I. Lazzizzera37, A. Lebedev9, H. T. Lee43, S. C. Lee43, C. Leluc16, H. L. Li43,**, J. Q. Li31, Q. Li31, Q. Li9,††, T. X. Li18, W. Li4, Y. Li16,∥, Z. H. Li6, Z. Y. Li43,∥, S. Lim40, C. H. Lin43, P. Lipari38, T. Lippert21, D. Liu43, H. Liu31, T. Lomtadze35, M. J. Lu37,‡‡, Y. S. Lu6, K. Luebelsmeyer1, F. Luo41, J. Z. Luo31, S. S. Lv18, R. Majka32, A. Malinin12, C. Mañá26, J. Marín26, T. Martin20, G. Martínez26, N. Masi7,8, D. Maurin17, A. Menchaca-Rocha27, Q. Meng31, D. C. Mo18, L. Morescalchi35,§§, P. Mott20, M. Müller1, J. Q. Ni18, N. Nikonov22, F. Nozzoli33, P. Nunes24, A. Obermeier1, A. Oliva26, M. Orcinha24, F. Palmonari7,8, C. Palomares26, M. Paniccia16, A. Papi33,34, E. Pedreschi35, S. Pensotti28,29, R. Pereira24,19, F. Pilo35, A. Piluso33,34, C. Pizzolotto33, V. Plyaskin9, M. Pohl16, V. Poireau3, E. Postaci2, A. Putze3, L. Quadrani7,8, X. M. Qi18, P. G. Rancoita28, D. Rapin16, J. S. Ricol17, I. Rodríguez26, S. Rosier-Lees3, A. Rozhkov9, D. Rozza28, R. Sagdeev11, J. Sandweiss32, P. Saouter16, C. Sbarra7,8, S. Schael1, S. M. Schmidt21, D. Schuckardt22, A. Schulz von Dratzig1, G. Schwering1, G. Scolieri33, E. S. Seo12, B. S. Shan4, Y. H. Shan4, J. Y. Shi31, X. Y. Shi9,∥∥, Y. M. Shi42, T. Siedenburg1, D. Son13, F. Spada38, F. Spinella35, W. Sun9, W. H. Sun9,¶¶, M. Tacconi28,29, C. P. Tang18, X. W. Tang6, Z. C. Tang6, L. Tao3, D. Tescaro23, Samuel C. C. Ting9, S. M. Ting9, N. Tomassetti17, J. Torsti44, C. Türkoğlu2, T. Urban20, V. Vagelli22, E. Valente38,39, C. Vannini35, E. Valtonen44, S. Vaurynovich9, M. Vecchi3, M. Velasco26, J. P. Vialle3, L. Q. Wang41, Q. L. Wang5, R. S. Wang42, X. Wang9, Z. X. Wang18, Z. L. Weng9, K. Whitman19, J. Wienkenhöver1, H. Wu31, X. Xia26,**, M. Xie9,††, S. Xie42, R. Q. Xiong31, G. M. Xin41, N. S. Xu18, W. Xu6,9, Q. Yan6, J. Yang40, M. Yang6, Q. H. Ye42, H. Yi31, Y. J. Yu5, Z. Q. Yu6, S. Zeissler22, J. H. Zhang31, M. T. Zhang18, X. B. Zhang18, Z. Zhang18, Z. M. Zheng4, H. L. Zhuang6, V. Zhukov1, A. Zichichi7,8, N. Zimmermann1, P. Zuccon9, and C. Zurbach30 (AMS Collaboration)

  • 1I. Physics Institute and JARA-FAME, RWTH Aachen University, D-52056 Aachen, Germany
  • 2Department of Physics, Middle East Technical University (METU), 06800 Ankara, Turkey
  • 3Laboratoire d’Annecy-Le-Vieux de Physique des Particules (LAPP), IN2P3/CNRS and Université de Savoie, F–74941 Annecy-le-Vieux, France
  • 4Beihang University (BUAA), Beijing 100191, China
  • 5Institute of Electrical Engineering (IEE), Chinese Academy of Sciences, Beijing 100080, China
  • 6Institute of High Energy Physics (IHEP), Chinese Academy of Sciences, Beijing, 100039, China
  • 7INFN-Sezione di Bologna, I-40126 Bologna, Italy
  • 8Università di Bologna, I-40126 Bologna, Italy
  • 9Massachusetts Institute of Technology (MIT), Cambridge, Massachusetts 02139, USA
  • 10National Central University (NCU), Chung-Li, Tao Yuan 32054, Taiwan
  • 11East-West Center for Space Science, University of Maryland, College Park, Maryland 20742, USA
  • 12IPST, University of Maryland, College Park, Maryland 20742, USA
  • 13CHEP, Kyungpook National University, 702-701 Daegu, Korea
  • 14CNR-IROE, I-50125 Firenze, Italy
  • 15European Organization for Nuclear Research, CERN, CH-1211 Geneva 23, Switzerland
  • 16DPNC, Université de Genève, CH-1211 Genève 4, Switzerland
  • 17Laboratoire de Physique subatomique et de cosmologie (LPSC), Université Grenoble-Alpes, CNRS/IN2P3, F-38026 Grenoble, France
  • 18Sun Yat-Sen University, SYSU, Guangzhou 510275, China
  • 19University of Hawaii, Physics and Astronomy Department, 2505 Correa Road, WAT 432, Honolulu, Hawaii 96822, USA
  • 20National Aeronautics and Space Administration (NASA), Johnson Space Center and Jacobs-Sverdrup, Houston, Texas 77058, USA
  • 21Jülich Supercomputing Centre and JARA-FAME, Research Centre Jülich, D-52425 Jülich, Germany
  • 22Institut für Experimentelle Kernphysik, Karlsruhe Institute of Technology (KIT), D-76128 Karlsruhe, Germany
  • 23Instituto de Astrofísica de Canarias (IAC), E-38205 La Laguna, Tenerife, Spain
  • 24Laboratório de Instrumentação e Física Experimental de Partículas, LIP, P-1000 Lisboa, Portugal
  • 25National Chung-Shan Institute of Science and Technology (NCSIST), Longtan, Tao Yuan 325, Taiwan
  • 26Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas (CIEMAT), E-28040 Madrid, Spain
  • 27Instituto de Física, Universidad Nacional Autónoma de México (UNAM), México, D.F., 01000 México
  • 28INFN-Sezione di Milano-Bicocca, I-20126 Milano, Italy
  • 29Università di Milano-Bicocca, I-20126 Milano, Italy
  • 30Laboratoire Univers et Particules de Montpellier (LUPM), IN2P3/CNRS and Université de Montpellier II, F-34095 Montpellier, France
  • 31Southeast University, SEU, Nanjing 210096, China
  • 32Physics Department, Yale University, New Haven, Connecticut 06520, USA
  • 33INFN-Sezione di Perugia, I-06100 Perugia, Italy
  • 34Università di Perugia, I-06100 Perugia, Italy
  • 35INFN-Sezione di Pisa, I-56100 Pisa, Italy
  • 36Università di Pisa, I-56100 Pisa, Italy
  • 37INFN–TIFPA and Università di Trento, I-38123 Povo, Trento, Italy
  • 38INFN-Sezione di Roma 1, I-00185 Roma, Italy
  • 39Università di Roma La Sapienza, I-00185 Roma, Italy
  • 40Department of Physics, Ewha Womans University, Seoul 120-750, Korea
  • 41Shandong University, SDU, Jinan, Shandong 250100, China
  • 42Shanghai Jiaotong University (SJTU), Shanghai 200030, China
  • 43Institute of Physics, Academia Sinica, Nankang, Taipei 11529, Taiwan
  • 44Space Research Laboratory, Department of Physics and Astronomy, University of Turku, FI-20014 Turku, Finland

  • *Deceased.
  • †Current address: ISDC, CH-1290 Versoix, Switzerland.
  • ‡Also at ASI, Rome I-00133, Italy.
  • §Also at Xi’an Jiaotong University, XJTU, Xi’an 710049, China.
  • ∥Also at Sun Yat-Sen University, SYSU, Guangzhou 510275, China.
  • Current address: European Organization for Nuclear Research, CERN, CH-1211 Geneva 23, Switzerland.
  • **Also at Shandong University, SDU, Jinan, Shandong 250100, China.
  • ††Also at Harbin Institute of Technology, HIT, Harbin 150001, China.
  • ‡‡Also at University of Science and Technology of China, USTC, Hefei, 230026, China.
  • §§Also at Università di Siena, I-53100 Siena, Italy.
  • ∥∥Also at Beijing Normal University, BNU, Beijing 100875, China.
  • ¶¶Also at Southeast University, SEU, Nanjing 210096, China.

Phys. Rev. Lett. 113, 121102 – Published 18 September, 2014

DOI: https://doi.org/10.1103/PhysRevLett.113.121102

Abstract

Precision measurements by the Alpha Magnetic Spectrometer on the International Space Station of the primary cosmic-ray electron flux in the range 0.5 to 700 GeV and the positron flux in the range 0.5 to 500 GeV are presented. The electron flux and the positron flux each require a description beyond a single power-law spectrum. Both the electron flux and the positron flux change their behavior at ∼30  GeV but the fluxes are significantly different in their magnitude and energy dependence. Between 20 and 200 GeV the positron spectral index is significantly harder than the electron spectral index. The determination of the differing behavior of the spectral indices versus energy is a new observation and provides important information on the origins of cosmic-ray electrons and positrons.

Synopsis

More Dark Matter Hints from Cosmic Rays?

Published 18 September, 2014

A particle detector onboard the International Space Station has revealed differences between the spectrum of cosmic-ray positrons and electrons, which might be a hint of dark matter annihilation processes.

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