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

M Aguilar; G Alberti; B Alpat; A Alvino; G Ambrosi; K Andeen; H Anderhub; L Arruda; P Azzarello; A Bachlechner; F Barao; B Baret; A Barrau; L Barrin; A Bartoloni; L Basara; A Basili; L Batalha; J Bates; R Battiston; J Bazo; R Becker; U Becker; M Behlmann; B Beischer; J Berdugo; P Berges; B Bertucci; G Bigongiari; A Biland; V Bindi; S Bizzaglia; G Boella; W de Boer; K Bollweg; J Bolmont; B Borgia; S Borsini; M J Boschini; G Boudoul; M Bourquin; P Brun; M Buénerd; J Burger; W Burger; F Cadoux; X D Cai; M Capell; D Casadei; J Casaus; V Cascioli; G Castellini; I Cernuda; F Cervelli; M J Chae; Y H Chang; A I Chen; C R Chen; H Chen; G M Cheng; H S Chen; L Cheng; N Chernoplyiokov; A Chikanian; E Choumilov; V Choutko; C H Chung; C Clark; R Clavero; G Coignet; V Commichau; C Consolandi; A Contin; C Corti; M T Costado Dios; B Coste; D Crespo; Z Cui; M Dai; C Delgado; S Della Torre; B Demirkoz; P Dennett; L Derome; S Di Falco; X H Diao; A Diago; L Djambazov; C Díaz; P von Doetinchem; W J Du; J M Dubois; R Duperay; M Duranti; D D'Urso; A Egorov; A Eline; F J Eppling; T Eronen; J van Es; H Esser; A Falvard; E Fiandrini; A Fiasson; E Finch; P Fisher; K Flood; R Foglio; M Fohey; S Fopp; N Fouque; Y Galaktionov; M Gallilee; L Gallin-Martel; G Gallucci; B García; J García; R García-López; L García-Tabares; C Gargiulo; H Gast; I Gebauer; S Gentile; M Gervasi; W Gillard; F Giovacchini; L Girard; P Goglov; J Gong; C Goy-Henningsen; D Grandi; M Graziani; A Grechko; A Gross; I Guerri; C de la Guía; K H Guo; M Habiby; S Haino; F Hauler; Z H He; M Heil; J Heilig; R Hermel; H Hofer; Z C Huang; W Hungerford; M Incagli; M Ionica; A Jacholkowska; W Y Jang; H Jinchi; M Jongmanns; L Journet; L Jungermann; W Karpinski; G N Kim; K S Kim; Th Kirn; R Kossakowski; A Koulemzine; O Kounina; A Kounine; V Koutsenko; M S Krafczyk; E Laudi; G Laurenti; C Lauritzen; A Lebedev; M W Lee; S C Lee; C Leluc; H León Vargas; V Lepareur; J Q Li; Q Li; T X Li; W Li; Z H Li; P Lipari; C H Lin; D Liu; H Liu; T Lomtadze; Y S Lu; S Lucidi; K Lübelsmeyer; J Z Luo; W Lustermann; S Lv; J Madsen; R Majka; A Malinin; C Mañá; J Marín; T Martin; G Martínez; F Masciocchi; N Masi; D Maurin; A McInturff; P McIntyre; A Menchaca-Rocha; Q Meng; M Menichelli; I Mereu; M Millinger; D C Mo; M Molina; P Mott; A Mujunen; S Natale; P Nemeth; J Q Ni; N Nikonov; F Nozzoli; P Nunes; A Obermeier; S Oh; A Oliva; F Palmonari; C Palomares; M Paniccia; A Papi; W H Park; M Pauluzzi; F Pauss; A Pauw; E Pedreschi; S Pensotti; R Pereira; E Perrin; G Pessina; G Pierschel; F Pilo; A Piluso; C Pizzolotto; V Plyaskin; J Pochon; M Pohl; V Poireau; S Porter; J Pouxe; A Putze; L Quadrani; X N Qi; P G Rancoita; D Rapin; Z L Ren; J S Ricol; E Riihonen; I Rodríguez; U Roeser; S Rosier-Lees; L Rossi; A Rozhkov; D Rozza; A Sabellek; R Sagdeev; J Sandweiss; B Santos; P Saouter; M Sarchioni; S Schael; D Schinzel; M Schmanau; G Schwering; A Schulz von Dratzig; G Scolieri; E S Seo; B S Shan; J Y Shi; Y M Shi; T Siedenburg; R Siedling; D Son; F Spada; F Spinella; M Steuer; K Stiff; W Sun; W H Sun; X H Sun; M Tacconi; C P Tang; X W Tang; Z C Tang; L Tao; J Tassan-Viol; Samuel C C Ting; S M Ting; C Titus; N Tomassetti; F Toral; J Torsti; J R Tsai; J C Tutt; J Ulbricht; T Urban; V Vagelli; E Valente; C Vannini; E Valtonen; M Vargas Trevino; S Vaurynovich; M Vecchi; M Vergain; B Verlaat; C Vescovi; J P Vialle; G Viertel; G Volpini; D Wang; N H Wang; Q L Wang; R S Wang; X Wang; Z X Wang; W Wallraff; Z L Weng; M Willenbrock; M Wlochal; H Wu; K Y Wu; Z S Wu; W J Xiao; S Xie; R Q Xiong; G M Xin; N S Xu; W Xu; Q Yan; J Yang; M Yang; Q H Ye; H Yi; Y J Yu; Z Q Yu; S Zeissler; J G Zhang; Z Zhang; M M Zhang; Z M Zheng; H L Zhuang; V Zhukov; A Zichichi; P Zuccon; C Zurbach; AMS Collaboration

doi:10.1103/PhysRevLett.110.141102

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

Phys Rev Lett. 2013 Apr 5;110(14):141102. doi: 10.1103/PhysRevLett.110.141102. Epub 2013 Apr 3.

Authors

M Aguilar¹, G Alberti², B Alpat³, A Alvino², G Ambrosi³, K Andeen⁴, H Anderhub⁵, L Arruda⁶, P Azzarello⁷, A Bachlechner⁸, F Barao⁶, B Baret⁹, A Barrau⁹, L Barrin¹⁰, A Bartoloni¹¹, L Basara¹², A Basili¹³, L Batalha⁶, J Bates¹⁴, R Battiston¹⁵, J Bazo³, R Becker¹³, U Becker¹³, M Behlmann¹³, B Beischer⁸, J Berdugo¹⁶, P Berges¹³, B Bertucci², G Bigongiari¹⁷, A Biland⁵, V Bindi¹⁸, S Bizzaglia³, G Boella¹⁹, W de Boer⁴, K Bollweg¹⁴, J Bolmont²⁰, B Borgia²¹, S Borsini², M J Boschini²², G Boudoul⁹, M Bourquin²³, P Brun¹², M Buénerd⁹, J Burger¹³, W Burger²⁴, F Cadoux²⁵, X D Cai¹³, M Capell¹³, D Casadei²⁶, J Casaus¹⁶, V Cascioli², G Castellini²⁷, I Cernuda¹⁶, F Cervelli²⁸, M J Chae²⁹, Y H Chang³⁰, A I Chen¹³, C R Chen³¹, H Chen¹³, G M Cheng³², H S Chen³², L Cheng³³, N Chernoplyiokov³⁴, A Chikanian³⁵, E Choumilov¹³, V Choutko¹³, C H Chung⁸, C Clark¹⁴, R Clavero³⁶, G Coignet¹², V Commichau⁵, C Consolandi³⁷, A Contin²⁶, C Corti¹⁸, M T Costado Dios³⁶, B Coste⁹, D Crespo¹⁶, Z Cui³³, M Dai³⁸, C Delgado¹⁶, S Della Torre¹⁹, B Demirkoz³⁹, P Dennett¹³, L Derome⁹, S Di Falco²⁸, X H Diao⁴⁰, A Diago³⁶, L Djambazov⁵, C Díaz¹⁶, P von Doetinchem⁸, W J Du³³, J M Dubois¹², R Duperay⁹, M Duranti², D D'Urso⁴¹, A Egorov¹³, A Eline¹³, F J Eppling¹³, T Eronen⁴², J van Es⁴³, H Esser⁸, A Falvard²⁰, E Fiandrini², A Fiasson¹², E Finch³⁵, P Fisher¹³, K Flood¹³, R Foglio⁹, M Fohey¹⁴, S Fopp⁸, N Fouque¹², Y Galaktionov¹³, M Gallilee¹³, L Gallin-Martel⁹, G Gallucci²⁸, B García¹⁶, J García¹⁶, R García-López³⁶, L García-Tabares¹⁶, C Gargiulo⁴⁴, H Gast⁸, I Gebauer⁴, S Gentile²¹, M Gervasi¹⁹, W Gillard⁹, F Giovacchini¹⁶, L Girard¹², P Goglov¹³, J Gong⁴⁵, C Goy-Henningsen¹², D Grandi²², M Graziani², A Grechko³⁴, A Gross⁸, I Guerri¹⁷, C de la Guía¹⁶, K H Guo⁴⁰, M Habiby²³, S Haino⁴⁶, F Hauler⁴, Z H He⁴⁰, M Heil⁴, J Heilig¹⁴, R Hermel¹², H Hofer⁵, Z C Huang⁴⁰, W Hungerford⁴⁷, M Incagli⁴⁸, M Ionica², A Jacholkowska²⁰, W Y Jang⁴⁹, H Jinchi⁵⁰, M Jongmanns⁵, L Journet¹², L Jungermann⁴, W Karpinski⁸, G N Kim⁴⁹, K S Kim⁴⁹, Th Kirn⁸, R Kossakowski¹², A Koulemzine¹³, O Kounina¹³, A Kounine¹³, V Koutsenko¹³, M S Krafczyk¹³, E Laudi², G Laurenti⁵¹, C Lauritzen¹⁴, A Lebedev¹³, M W Lee⁴⁹, S C Lee⁵², C Leluc²³, H León Vargas⁵³, V Lepareur¹², J Q Li⁴⁵, Q Li⁴⁵, T X Li⁴⁰, W Li⁵⁴, Z H Li³², P Lipari¹¹, C H Lin⁵², D Liu⁵², H Liu⁴⁵, T Lomtadze²⁸, Y S Lu³², S Lucidi³, K Lübelsmeyer⁸, J Z Luo⁴⁵, W Lustermann⁵, S Lv⁴⁰, J Madsen⁵⁵, R Majka³⁵, A Malinin⁵⁶, C Mañá¹⁶, J Marín¹⁶, T Martin¹⁴, G Martínez¹⁶, F Masciocchi²³, N Masi²⁶, D Maurin⁹, A McInturff⁵⁷, P McIntyre⁵⁷, A Menchaca-Rocha⁵³, Q Meng⁴⁵, M Menichelli³, I Mereu², M Millinger⁸, D C Mo⁴⁰, M Molina⁵⁸, P Mott¹⁴, A Mujunen⁵⁹, S Natale⁶⁰, P Nemeth¹⁴, J Q Ni⁴⁰, N Nikonov⁴, F Nozzoli⁶¹, P Nunes⁶, A Obermeier⁴, S Oh²⁹, A Oliva⁶², F Palmonari²⁶, C Palomares¹⁶, M Paniccia²⁵, A Papi³, W H Park⁴⁹, M Pauluzzi², F Pauss⁵, A Pauw⁴³, E Pedreschi²⁸, S Pensotti¹⁹, R Pereira⁶, E Perrin²³, G Pessina¹⁹, G Pierschel⁸, F Pilo²⁸, A Piluso², C Pizzolotto⁶¹, V Plyaskin¹³, J Pochon⁶³, M Pohl²³, V Poireau¹², S Porter¹⁴, J Pouxe⁹, A Putze⁸, L Quadrani²⁶, X N Qi⁴⁰, P G Rancoita²², D Rapin²³, Z L Ren⁵², J S Ricol⁹, E Riihonen⁴², I Rodríguez¹⁶, U Roeser⁵, S Rosier-Lees¹², L Rossi⁶⁴, A Rozhkov¹³, D Rozza⁶⁵, A Sabellek⁴, R Sagdeev⁶⁶, J Sandweiss³⁵, B Santos⁶, P Saouter²³, M Sarchioni³, S Schael⁸, D Schinzel¹³, M Schmanau⁴, G Schwering⁸, A Schulz von Dratzig⁸, G Scolieri³, E S Seo⁵⁶, B S Shan⁵⁴, J Y Shi⁴⁵, Y M Shi⁶⁷, T Siedenburg⁸, R Siedling⁸, D Son⁴⁹, F Spada¹¹, F Spinella²⁸, M Steuer¹³, K Stiff⁵⁷, W Sun¹³, W H Sun⁴⁵, X H Sun⁴⁰, M Tacconi¹⁹, C P Tang⁴⁰, X W Tang³², Z C Tang³², L Tao¹², J Tassan-Viol¹², Samuel C C Ting¹³, S M Ting¹³, C Titus¹³, N Tomassetti², F Toral¹⁶, J Torsti⁴², J R Tsai³¹, J C Tutt¹⁴, J Ulbricht⁵, T Urban¹⁴, V Vagelli⁴, E Valente¹¹, C Vannini²⁸, E Valtonen⁴², M Vargas Trevino⁹, S Vaurynovich¹³, M Vecchi³⁰, M Vergain¹³, B Verlaat⁶⁸, C Vescovi⁹, J P Vialle¹², G Viertel⁵, G Volpini⁶⁹, D Wang³¹, N H Wang³³, Q L Wang³⁸, R S Wang⁶⁷, X Wang¹³, Z X Wang⁴⁰, W Wallraff⁸, Z L Weng⁷⁰, M Willenbrock¹³, M Wlochal⁸, H Wu⁴⁵, K Y Wu⁷¹, Z S Wu⁴⁰, W J Xiao⁴⁰, S Xie⁶⁷, R Q Xiong⁴⁵, G M Xin³³, N S Xu⁴⁰, W Xu³², Q Yan³², J Yang²⁹, M Yang³², Q H Ye⁶⁷, H Yi⁴⁵, Y J Yu³⁸, Z Q Yu³², S Zeissler⁴, J G Zhang⁴⁵, Z Zhang⁴⁰, M M Zhang⁴⁰, Z M Zheng⁵⁴, H L Zhuang³², V Zhukov⁸, A Zichichi²⁶, P Zuccon⁷², C Zurbach²⁰; AMS Collaboration

Affiliations

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.

PMID: 25166975
DOI: 10.1103/PhysRevLett.110.141102

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.