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Phys Rev Lett. 2013 Apr 5;110(14):141102. Epub 2013 Apr 3.

First result from the Alpha Magnetic Spectrometer on the International Space Station: precision measurement of the positron fraction in primary cosmic rays of 0.5-350 GeV.

Aguilar M1, Alberti G2, Alpat B3, Alvino A2, Ambrosi G3, Andeen K4, Anderhub H5, Arruda L6, Azzarello P7, Bachlechner A8, Barao F6, Baret B9, Barrau A9, Barrin L10, Bartoloni A11, Basara L12, Basili A13, Batalha L6, Bates J14, Battiston R15, Bazo J3, Becker R13, Becker U13, Behlmann M13, Beischer B8, Berdugo J16, Berges P13, Bertucci B2, Bigongiari G17, Biland A5, Bindi V18, Bizzaglia S3, Boella G19, de Boer W4, Bollweg K14, Bolmont J20, Borgia B21, Borsini S2, Boschini MJ22, Boudoul G9, Bourquin M23, Brun P12, Buénerd M9, Burger J13, Burger W24, Cadoux F25, Cai XD13, Capell M13, Casadei D26, Casaus J16, Cascioli V2, Castellini G27, Cernuda I16, Cervelli F28, Chae MJ29, Chang YH30, Chen AI13, Chen CR31, Chen H13, Cheng GM32, Chen HS32, Cheng L33, Chernoplyiokov N34, Chikanian A35, Choumilov E13, Choutko V13, Chung CH8, Clark C14, Clavero R36, Coignet G12, Commichau V5, Consolandi C37, Contin A26, Corti C18, Costado Dios MT36, Coste B9, Crespo D16, Cui Z33, Dai M38, Delgado C16, Della Torre S19, Demirkoz B39, Dennett P13, Derome L9, Di Falco S28, Diao XH40, Diago A36, Djambazov L5, Díaz C16, von Doetinchem P8, Du WJ33, Dubois JM12, Duperay R9, Duranti M2, D'Urso D41, Egorov A13, Eline A13, Eppling FJ13, Eronen T42, van Es J43, Esser H8, Falvard A20, Fiandrini E2, Fiasson A12, Finch E35, Fisher P13, Flood K13, Foglio R9, Fohey M14, Fopp S8, Fouque N12, Galaktionov Y13, Gallilee M13, Gallin-Martel L9, Gallucci G28, García B16, García J16, García-López R36, García-Tabares L16, Gargiulo C44, Gast H8, Gebauer I4, Gentile S21, Gervasi M19, Gillard W9, Giovacchini F16, Girard L12, Goglov P13, Gong J45, Goy-Henningsen C12, Grandi D22, Graziani M2, Grechko A34, Gross A8, Guerri I17, de la Guía C16, Guo KH40, Habiby M23, Haino S46, Hauler F4, He ZH40, Heil M4, Heilig J14, Hermel R12, Hofer H5, Huang ZC40, Hungerford W47, Incagli M48, Ionica M2, Jacholkowska A20, Jang WY49, Jinchi H50, Jongmanns M5, Journet L12, Jungermann L4, Karpinski W8, Kim GN49, Kim KS49, Kirn T8, Kossakowski R12, Koulemzine A13, Kounina O13, Kounine A13, Koutsenko V13, Krafczyk MS13, Laudi E2, Laurenti G51, Lauritzen C14, Lebedev A13, Lee MW49, Lee SC52, Leluc C23, León Vargas H53, Lepareur V12, Li JQ45, Li Q45, Li TX40, Li W54, Li ZH32, Lipari P11, Lin CH52, Liu D52, Liu H45, Lomtadze T28, Lu YS32, Lucidi S3, Lübelsmeyer K8, Luo JZ45, Lustermann W5, Lv S40, Madsen J55, Majka R35, Malinin A56, Mañá C16, Marín J16, Martin T14, Martínez G16, Masciocchi F23, Masi N26, Maurin D9, McInturff A57, McIntyre P57, Menchaca-Rocha A53, Meng Q45, Menichelli M3, Mereu I2, Millinger M8, Mo DC40, Molina M58, Mott P14, Mujunen A59, Natale S60, Nemeth P14, Ni JQ40, Nikonov N4, Nozzoli F61, Nunes P6, Obermeier A4, Oh S29, Oliva A62, Palmonari F26, Palomares C16, Paniccia M25, Papi A3, Park WH49, Pauluzzi M2, Pauss F5, Pauw A43, Pedreschi E28, Pensotti S19, Pereira R6, Perrin E23, Pessina G19, Pierschel G8, Pilo F28, Piluso A2, Pizzolotto C61, Plyaskin V13, Pochon J63, Pohl M23, Poireau V12, Porter S14, Pouxe J9, Putze A8, Quadrani L26, Qi XN40, Rancoita PG22, Rapin D23, Ren ZL52, Ricol JS9, Riihonen E42, Rodríguez I16, Roeser U5, Rosier-Lees S12, Rossi L64, Rozhkov A13, Rozza D65, Sabellek A4, Sagdeev R66, Sandweiss J35, Santos B6, Saouter P23, Sarchioni M3, Schael S8, Schinzel D13, Schmanau M4, Schwering G8, Schulz von Dratzig A8, Scolieri G3, Seo ES56, Shan BS54, Shi JY45, Shi YM67, Siedenburg T8, Siedling R8, Son D49, Spada F11, Spinella F28, Steuer M13, Stiff K57, Sun W13, Sun WH45, Sun XH40, Tacconi M19, Tang CP40, Tang XW32, Tang ZC32, Tao L12, Tassan-Viol J12, Ting SC13, Ting SM13, Titus C13, Tomassetti N2, Toral F16, Torsti J42, Tsai JR31, Tutt JC14, Ulbricht J5, Urban T14, Vagelli V4, Valente E11, Vannini C28, Valtonen E42, Vargas Trevino M9, Vaurynovich S13, Vecchi M30, Vergain M13, Verlaat B68, Vescovi C9, Vialle JP12, Viertel G5, Volpini G69, Wang D31, Wang NH33, Wang QL38, Wang RS67, Wang X13, Wang ZX40, Wallraff W8, Weng ZL70, Willenbrock M13, Wlochal M8, Wu H45, Wu KY71, Wu ZS40, Xiao WJ40, Xie S67, Xiong RQ45, Xin GM33, Xu NS40, Xu W32, Yan Q32, Yang J29, Yang M32, Ye QH67, Yi H45, Yu YJ38, Yu ZQ32, Zeissler S4, Zhang JG45, Zhang Z40, Zhang MM40, Zheng ZM54, Zhuang HL32, Zhukov V8, Zichichi A26, Zuccon P72, Zurbach C20; AMS Collaboration.

Author information

1
European Organization for Nuclear Research, CERN, CH-1211 Geneva 23, Switzerland and Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas, CIEMAT, E-28040 Madrid, Spain.
2
INFN-Sezione di Perugia, I-06100 Perugia, Italy and Università di Perugia, I-06100 Perugia, Italy.
3
INFN-Sezione di Perugia, I-06100 Perugia, Italy.
4
Institut für Experimentelle Kernphysik, Karlsruhe Institute of Technology, KIT, D-76128 Karlsruhe, Germany.
5
Institute for Particle Physics, ETH Zürich, CH-8093 Zürich, Switzerland.
6
Laboratório de Instrumentação e Física Experimental de Partículas, LIP, P-1000 Lisboa, Portugal.
7
DPNC, Université de Genève, CH-1211 Genève 4, Switzerland and INFN-Sezione di Perugia, I-06100 Perugia, Italy.
8
I. Physikalisches Institut B, RWTH, D-52056 Aachen, Germany.
9
Laboratoire de Physique subatomique et de cosmologie, LPSC, IN2P3/CNRS and Université Joseph Fourier, Grenoble INP, 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
Laboratoire d'Annecy-Le-Vieux de Physique des Particules, LAPP, IN2P3/CNRS and Université de Savoie, F-74941 Annecy-le-Vieux, France.
13
Massachusetts Institute of Technology, MIT, Cambridge, Massachusetts 02139, USA.
14
NASA, National Aeronautics and Space Administration, Johnson Space Center, JSC, and Jacobs-Sverdrup, Houston, Texas 77058, USA.
15
INFN-Sezione di Perugia, I-06100 Perugia, Italy and Università di Perugia, I-06100 Perugia, Italy and INFN-TIFPA and Università di Trento, I-38123 Povo, Trento, Italy.
16
Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas, CIEMAT, E-28040 Madrid, Spain.
17
INFN-Sezione di Pisa, I-56100 Pisa, Italy and Università di Pisa, I-56100 Pisa, Italy.
18
University of Hawaii, Physics and Astronomy Department, 2505 Correa Road, WAT 432; Honolulu, Hawaii 96822, USA.
19
INFN-Sezione di Milano-Bicocca, I-20126 Milano, Italy and Università di Milano-Bicocca, I-20126 Milano, Italy.
20
Laboratoire Univers et Particules de Montpellier, LUPM (ex LPTA), IN2P3/CNRS and Université de Montpellier II, F-34095 Montpellier, France.
21
INFN-Sezione di Roma 1, I-00185 Roma, Italy and Università di Roma La Sapienza, I-00185 Roma, Italy.
22
INFN-Sezione di Milano-Bicocca, I-20126 Milano, Italy.
23
DPNC, Université de Genève, CH-1211 Genève 4, Switzerland.
24
Università di Perugia, I-06100 Perugia, Italy.
25
Laboratoire d'Annecy-Le-Vieux de Physique des Particules, LAPP, IN2P3/CNRS and Université de Savoie, F-74941 Annecy-le-Vieux, France and DPNC, Université de Genève, CH-1211 Genève 4, Switzerland.
26
INFN-Sezione di Bologna, I-40126 Bologna, Italy and Università di Bologna, I-40126 Bologna, Italy.
27
CNR-IROE, I-50125 Firenze, Italy.
28
INFN-Sezione di Pisa, I-56100 Pisa, Italy.
29
Department of Physics, Ewha Womans University, Seoul, 120-750, Korea.
30
National Central University, NCU, Chung-Li, Tao Yuan 32054, Taiwan.
31
National Space Organization, Hsin-Chu City, 300, Taiwan.
32
Institute of High Energy Physics, IHEP, Chinese Academy of Sciences, Beijing, 100039, China.
33
Shandong University, SDU, Jinan, Shandong, 250100, China.
34
Kurchatov Institute, Russian Research Centre, Moscow, 123182, Russia.
35
Physics Department, Yale University, New Haven, Connecticut 06520, USA.
36
Instituto de Astrofísica de Canarias, IAC, E-38205, La Laguna, Tenerife, Spain.
37
University of Hawaii, Physics and Astronomy Department, 2505 Correa Road, WAT 432; Honolulu, Hawaii 96822, USA and INFN-Sezione di Milano-Bicocca, I-20126 Milano, Italy.
38
Institute of Electrical Engineering, IEE, Chinese Academy of Sciences, Beijing, 100080, China.
39
Department of Physics, Middle East Technical University, METU, 06800 Ankara, Turkey.
40
Sun Yat-sen University, SYSU, Guangzhou, 510275, China.
41
European Organization for Nuclear Research, CERN, CH-1211 Geneva 23, Switzerland and INFN-Sezione di Perugia, I-06100 Perugia, Italy.
42
Space Research Laboratory, Department of Physics, University of Turku, FIN-20014 Turku, Finland.
43
National Aerospace Laboratory, NLR, NL-8300 AD Emmeloord, Netherlands.
44
Massachusetts Institute of Technology, MIT, Cambridge, Massachusetts 02139, USA and INFN-Sezione di Roma 1, I-00185 Roma, Italy.
45
Southeast University, SEU, Nanjing, 210096, China.
46
National Central University, NCU, Chung-Li, Tao Yuan 32054, Taiwan and INFN-Sezione di Perugia, I-06100 Perugia, Italy.
47
Massachusetts Institute of Technology, MIT, Cambridge, Massachusetts 02139, USA and NASA, National Aeronautics and Space Administration, Johnson Space Center, JSC, and Jacobs-Sverdrup, Houston, Texas 77058, USA.
48
Massachusetts Institute of Technology, MIT, Cambridge, Massachusetts 02139, USA and INFN-Sezione di Pisa, I-56100 Pisa, Italy.
49
CHEP, Kyungpook National University, 702-701 Daegu, Korea.
50
Chung-Shan Institute of Science and Technology, Lung-Tan, Tao Yuan 325, Taiwan.
51
INFN-Sezione di Bologna, I-40126 Bologna, Italy.
52
Institute of Physics, Academia Sinica, Nankang, Taipei 11529, Taiwan.
53
Instituto de Física, Universidad Nacional Autónoma de México, UNAM, México, D. F., 01000 México.
54
Beihang University, BUAA, Beijing, 100191, China.
55
Department of Physics and Astronomy, University of Aarhus, DK-8000 Aarhus C, Denmark.
56
IPST, University of Maryland, College Park, Maryland 20742, USA.
57
Department of Physics, Texas A&M University, College Station, Texas 77843, USA.
58
I. Physikalisches Institut B, RWTH, D-52056 Aachen, Germany and Department of Physics and Astronomy, University of Aarhus, DK-8000 Aarhus C, Denmark and National Institute for Nuclear Physics and High Energy Physics, NIKHEF, NL-1098 SJ Amsterdam, Netherlands and Department of Physics, Middle East Technical University, METU, 06800 Ankara, Turkey and Laboratoire d'Annecy-Le-Vieux de Physique des Particules, LAPP, IN2P3/CNRS and Université de Savoie, F-74941 Annecy-le-Vieux, France and Beihang University, BUAA, Beijing, 100191, China and Institute of Electrical Engineering, IEE, Chinese Academy of Sciences, Beijing, 100080, China and Institute of High Energy Physics, IHEP, Chinese Academy of Sciences, Beijing, 100039, China and INFN-Sezione di Bologna, I-40126 Bologna, Italy and Università di Bologna, I-40126 Bologna, Italy and Massachusetts Institute of Technology, MIT, Cambridge, Massachusetts 02139, USA and National Central University, NCU, Chung-Li, Tao Yuan 32054, Taiwan and East-West Center for Space Science, University of Maryland, College Park, Maryland 20742, USA and IPST, University of Maryland, College Park, Maryland 20742, USA and Department of Physics, Texas A&M University, College Station, Texas 77843, USA and CHEP, Kyungpook National University, 702-701 Daegu, Korea and National Aerospace Laboratory, NLR, NL-8300 AD Emmeloord, Netherlands and CNR-IROE, I-50125 Firenze, Italy and ASDC ESRIN, I-00044 Frascati, Italy and European Organization for Nuclear Research, CERN, CH-1211 Geneva 23, Switzerland and DPNC, Université de Genève, CH-1211 Genève 4, Switzerland and Laboratoire de Physique subatomique et de cosmologie, LPSC, IN2P3/CNRS and Université Joseph Fourier, Grenoble INP, F-38026 Grenoble, France and Sun Yat-sen University, SYSU, Guangzhou, 510275, China and University of Hawaii, Physics and Astronomy Department, 2505 Correa Road, WAT 432; Honolulu, Hawaii 96822, USA and NASA, National Aeronautics and Space Administration, Johnson Space Center,
59
Metsahovi Radio Observatory, Helsinki University of Technology, FIN-02540 Kylmala, Finland.
60
I. Physikalisches Institut B, RWTH, D-52056 Aachen, Germany and Institute of Physics, Academia Sinica, Nankang, Taipei 11529, Taiwan.
61
ASDC ESRIN, I-00044 Frascati, Italy and INFN-Sezione di Perugia, I-06100 Perugia, Italy.
62
Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas, CIEMAT, E-28040 Madrid, Spain and INFN-Sezione di Perugia, I-06100 Perugia, Italy and Università di Perugia, I-06100 Perugia, Italy.
63
Laboratoire d'Annecy-Le-Vieux de Physique des Particules, LAPP, IN2P3/CNRS and Université de Savoie, F-74941 Annecy-le-Vieux, France and Instituto de Astrofísica de Canarias, IAC, E-38205, La Laguna, Tenerife, Spain.
64
European Organization for Nuclear Research, CERN, CH-1211 Geneva 23, Switzerland and Università di Milano, I-20090 Milano, Italy.
65
European Organization for Nuclear Research, CERN, CH-1211 Geneva 23, Switzerland and INFN-Sezione di Milano-Bicocca, I-20126 Milano, Italy and Università di Milano-Bicocca, I-20126 Milano, Italy.
66
East-West Center for Space Science, University of Maryland, College Park, Maryland 20742, USA.
67
Shanghai Jiaotong University, SJTU, Shanghai, 200030, China.
68
National Institute for Nuclear Physics and High Energy Physics, NIKHEF, NL-1098 SJ Amsterdam, Netherlands.
69
INFN-Sezione di Milano, I-20090 Milano, Italy and Università di Milano, I-20090 Milano, Italy.
70
Sun Yat-sen University, SYSU, Guangzhou, 510275, China and Institute of Physics, Academia Sinica, Nankang, Taipei 11529, Taiwan.
71
Beihang University, BUAA, Beijing, 100191, China and Institute of Physics, Academia Sinica, Nankang, Taipei 11529, Taiwan.
72
Massachusetts Institute of Technology, MIT, Cambridge, Massachusetts 02139, USA and INFN-Sezione di Perugia, I-06100 Perugia, Italy.

Abstract

A precision measurement by the Alpha Magnetic Spectrometer on the International Space Station of the positron fraction in primary cosmic rays in the energy range from 0.5 to 350 GeV based on 6.8 × 10(6) positron and electron events is presented. The very accurate data show that the positron fraction is steadily increasing from 10 to ∼ 250  GeV, but, from 20 to 250 GeV, the slope decreases by an order of magnitude. The positron fraction spectrum shows no fine structure, and the positron to electron ratio shows no observable anisotropy. Together, these features show the existence of new physical phenomena.

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