Inferred cosmic-ray spectrum from Fermi large area telescope γ-ray observations of Earth's limb

M Ackermann; M Ajello; A Albert; A Allafort; L Baldini; G Barbiellini; D Bastieri; K Bechtol; R Bellazzini; R D Blandford; E D Bloom; E Bonamente; E Bottacini; A Bouvier; T J Brandt; M Brigida; P Bruel; R Buehler; S Buson; G A Caliandro; R A Cameron; P A Caraveo; C Cecchi; E Charles; R C G Chaves; A Chekhtman; J Chiang; G Chiaro; S Ciprini; R Claus; J Cohen-Tanugi; J Conrad; S Cutini; M Dalton; F D'Ammando; A de Angelis; F de Palma; C D Dermer; S W Digel; L Di Venere; E do Couto e Silva; P S Drell; A Drlica-Wagner; C Favuzzi; S J Fegan; E C Ferrara; W B Focke; A Franckowiak; Y Fukazawa; S Funk; P Fusco; F Gargano; D Gasparrini; S Germani; N Giglietto; F Giordano; M Giroletti; T Glanzman; G Godfrey; G A Gomez-Vargas; I A Grenier; J E Grove; S Guiriec; M Gustafsson; D Hadasch; Y Hanabata; A K Harding; M Hayashida; K Hayashi; J W Hewitt; D Horan; X Hou; R E Hughes; Y Inoue; M S Jackson; T Jogler; G Jóhannesson; A S Johnson; T Kamae; T Kawano; J Knödlseder; M Kuss; J Lande; S Larsson; L Latronico; F Longo; F Loparco; M N Lovellette; P Lubrano; M Mayer; M N Mazziotta; J E McEnery; J Mehault; P F Michelson; W Mitthumsiri; T Mizuno; A A Moiseev; C Monte; M E Monzani; A Morselli; I V Moskalenko; S Murgia; R Nemmen; E Nuss; T Ohsugi; A Okumura; M Orienti; E Orlando; J F Ormes; D Paneque; J H Panetta; J S Perkins; M Pesce-Rollins; F Piron; G Pivato; T A Porter; S Rainò; R Rando; M Razzano; S Razzaque; A Reimer; O Reimer; S Ritz; M Roth; M Schaal; A Schulz; C Sgrò; E J Siskind; G Spandre; P Spinelli; A W Strong; H Takahashi; Y Takeuchi; J G Thayer; J B Thayer; D J Thompson; L Tibaldo; M Tinivella; D F Torres; G Tosti; E Troja; V Tronconi; T L Usher; J Vandenbroucke; V Vasileiou; G Vianello; V Vitale; M Werner; B L Winer; K S Wood; M Wood; Z Yang; Fermi LAT Collaboration

doi:10.1103/PhysRevLett.112.151103

Inferred cosmic-ray spectrum from Fermi large area telescope γ-ray observations of Earth's limb

Phys Rev Lett. 2014 Apr 18;112(15):151103. doi: 10.1103/PhysRevLett.112.151103. Epub 2014 Apr 17.

Authors

M Ackermann¹, M Ajello², A Albert³, A Allafort³, L Baldini⁴, G Barbiellini⁵, D Bastieri⁶, K Bechtol³, R Bellazzini⁴, R D Blandford³, E D Bloom³, E Bonamente⁷, E Bottacini³, A Bouvier⁸, T J Brandt⁹, M Brigida¹⁰, P Bruel¹¹, R Buehler¹, S Buson⁶, G A Caliandro¹², R A Cameron³, P A Caraveo¹³, C Cecchi⁷, E Charles³, R C G Chaves¹⁴, A Chekhtman¹⁵, J Chiang³, G Chiaro¹⁶, S Ciprini¹⁷, R Claus³, J Cohen-Tanugi¹⁸, J Conrad¹⁹, S Cutini¹⁷, M Dalton²⁰, F D'Ammando²¹, A de Angelis²², F de Palma¹⁰, C D Dermer²³, S W Digel³, L Di Venere²⁴, E do Couto e Silva³, P S Drell³, A Drlica-Wagner²⁵, C Favuzzi¹⁰, S J Fegan¹¹, E C Ferrara⁹, W B Focke³, A Franckowiak³, Y Fukazawa²⁶, S Funk³, P Fusco¹⁰, F Gargano²⁷, D Gasparrini¹⁷, S Germani⁷, N Giglietto¹⁰, F Giordano¹⁰, M Giroletti²¹, T Glanzman³, G Godfrey³, G A Gomez-Vargas²⁸, I A Grenier¹⁴, J E Grove²³, S Guiriec⁹, M Gustafsson²⁹, D Hadasch³⁰, Y Hanabata³¹, A K Harding⁹, M Hayashida³¹, K Hayashi³², J W Hewitt⁹, D Horan¹¹, X Hou²⁰, R E Hughes³³, Y Inoue³, M S Jackson³⁴, T Jogler³, G Jóhannesson³⁵, A S Johnson³, T Kamae³, T Kawano²⁶, J Knödlseder³⁶, M Kuss⁴, J Lande³, S Larsson³⁷, L Latronico³⁸, F Longo⁵, F Loparco¹⁰, M N Lovellette²³, P Lubrano⁷, M Mayer¹, M N Mazziotta²⁷, J E McEnery³⁹, J Mehault²⁰, P F Michelson³, W Mitthumsiri⁴⁰, T Mizuno⁴¹, A A Moiseev⁴², C Monte¹⁰, M E Monzani³, A Morselli⁴³, I V Moskalenko³, S Murgia⁴⁴, R Nemmen⁴⁵, E Nuss¹⁸, T Ohsugi⁴¹, A Okumura⁴⁶, M Orienti²¹, E Orlando³, J F Ormes⁴⁷, D Paneque⁴⁸, J H Panetta³, J S Perkins⁹, M Pesce-Rollins⁴, F Piron¹⁸, G Pivato¹⁶, T A Porter³, S Rainò¹⁰, R Rando⁶, M Razzano⁴, S Razzaque⁴⁹, A Reimer⁵⁰, O Reimer⁵⁰, S Ritz⁸, M Roth⁵¹, M Schaal⁵², A Schulz¹, C Sgrò⁴, E J Siskind⁵³, G Spandre⁴, P Spinelli¹⁰, A W Strong⁵⁴, H Takahashi²⁶, Y Takeuchi⁵⁵, J G Thayer³, J B Thayer³, D J Thompson⁹, L Tibaldo³, M Tinivella⁴, D F Torres⁵⁶, G Tosti⁷, E Troja³⁹, V Tronconi¹⁶, T L Usher³, J Vandenbroucke³, V Vasileiou¹⁸, G Vianello³, V Vitale⁵⁷, M Werner³⁰, B L Winer³³, K S Wood²³, M Wood³, Z Yang⁵⁸; Fermi LAT Collaboration

Affiliations

¹ Deutsches Elektronen Synchrotron DESY, D-15738 Zeuthen, Germany.
² Space Sciences Laboratory, 7 Gauss Way, University of California, Berkeley, California 94720-7450, USA.
³ W. W. Hansen Experimental Physics Laboratory, Kavli Institute for Particle Astrophysics and Cosmology, Department of Physics and SLAC National Accelerator Laboratory, Stanford University, Stanford, California 94305, USA.
⁴ Istituto Nazionale di Fisica Nucleare, Sezione di Pisa, I-56127 Pisa, Italy.
⁵ Istituto Nazionale di Fisica Nucleare, Sezione di Trieste, I-34127 Trieste, Italy and Dipartimento di Fisica, Università di Trieste, I-34127 Trieste, Italy.
⁶ Istituto Nazionale di Fisica Nucleare, Sezione di Padova, I-35131 Padova, Italy and Dipartimento di Fisica e Astronomia "G. Galilei", Università di Padova, I-35131 Padova, Italy.
⁷ Istituto Nazionale di Fisica Nucleare, Sezione di Perugia, I-06123 Perugia, Italy and Dipartimento di Fisica, Università degli Studi di Perugia, I-06123 Perugia, Italy.
⁸ Santa Cruz Institute for Particle Physics, Department of Physics and Department of Astronomy and Astrophysics, University of California at Santa Cruz, Santa Cruz, California 95064, USA.
⁹ NASA Goddard Space Flight Center, Greenbelt, Maryland 20771, USA.
¹⁰ Dipartimento di Fisica "M. Merlin" dell'Università e del Politecnico di Bari, I-70126 Bari, Italy and Istituto Nazionale di Fisica Nucleare, Sezione di Bari, 70126 Bari, Italy.
¹¹ Laboratoire Leprince-Ringuet, École polytechnique, CNRS/IN2P3, Palaiseau, France.
¹² W. W. Hansen Experimental Physics Laboratory, Kavli Institute for Particle Astrophysics and Cosmology, Department of Physics and SLAC National Accelerator Laboratory, Stanford University, Stanford, California 94305, USA and Consorzio Interuniversitario per la Fisica Spaziale (CIFS), I-10133 Torino, Italy.
¹³ INAF-Istituto di Astrofisica Spaziale e Fisica Cosmica, I-20133 Milano, Italy.
¹⁴ Laboratoire AIM, CEA-IRFU/CNRS/Université Paris Diderot, Service d'Astrophysique, CEA Saclay, 91191 Gif sur Yvette, France.
¹⁵ Center for Earth Observing and Space Research, College of Science, George Mason University, Fairfax, Virginia 22030, USA.
¹⁶ Dipartimento di Fisica e Astronomia "G. Galilei", Università di Padova, I-35131 Padova, Italy.
¹⁷ Agenzia Spaziale Italiana (ASI) Science Data Center, I-00044 Frascati (Roma), Italy and Istituto Nazionale di Astrofisica - Osservatorio Astronomico di Roma, I-00040 Monte Porzio Catone (Roma), Italy.
¹⁸ Laboratoire Univers et Particules de Montpellier, Université Montpellier 2, CNRS/IN2P3 Montpellier, France.
¹⁹ Department of Physics, Stockholm University, AlbaNova, SE-106 91 Stockholm, Sweden and The Oskar Klein Centre for Cosmoparticle Physics, AlbaNova, SE-106 91 Stockholm, Sweden and The Royal Swedish Academy of Sciences, Box 50005, SE-104 05 Stockholm, Sweden.
²⁰ Centre d'Études Nucléaires de Bordeaux Gradignan, IN2P3/CNRS, Université Bordeaux 1, BP120, F-33175 Gradignan Cedex, France.
²¹ INAF Istituto di Radioastronomia, 40129 Bologna, Italy.
²² Dipartimento di Fisica, Università di Udine and Istituto Nazionale di Fisica Nucleare, Sezione di Trieste, Gruppo Collegato di Udine, I-33100 Udine, Italy.
²³ Space Science Division, Naval Research Laboratory, Washington, D.C. 20375-5352, USA.
²⁴ Dipartimento di Fisica "M. Merlin" dell'Università e del Politecnico di Bari, I-70126 Bari, Italy.
²⁵ Fermilab, Batavia, Illinois 60510, USA.
²⁶ Department of Physical Sciences, Hiroshima University, Higashi-Hiroshima, Hiroshima 739-8526, Japan.
²⁷ Istituto Nazionale di Fisica Nucleare, Sezione di Bari, 70126 Bari, Italy.
²⁸ Istituto Nazionale di Fisica Nucleare, Sezione di Roma "Tor Vergata", I-00133 Roma, Italy and Departamento de Física Teórica, Universidad Autónoma de Madrid, Cantoblanco, E-28049 Madrid, Spain and Instituto de Física Teórica IFT-UAM/CSIC, Universidad Autónoma de Madrid, Cantoblanco, E-28049 Madrid, Spain.
²⁹ Service de Physique Theorique, Universite Libre de Bruxelles (ULB), Bld du Triomphe, CP225, 1050 Brussels, Belgium.
³⁰ Institut für Astro- und Teilchenphysik and Institut für Theoretische Physik, Leopold-Franzens-Universität Innsbruck, A-6020 Innsbruck, Austria.
³¹ Institute for Cosmic-Ray Research, University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8582, Japan.
³² Institute of Space and Astronautical Science, JAXA, 3-1-1 Yoshinodai, Chuo-ku, Sagamihara, Kanagawa 252-5210, Japan.
³³ Department of Physics, Center for Cosmology and Astro-Particle Physics, The Ohio State University, Columbus, Ohio 43210, USA.
³⁴ The Oskar Klein Centre for Cosmoparticle Physics, AlbaNova, SE-106 91 Stockholm, Sweden and Department of Physics, KTH Royal Institute of Technology, AlbaNova, SE-106 91 Stockholm, Sweden.
³⁵ Science Institute, University of Iceland, IS-107 Reykjavik, Iceland.
³⁶ CNRS, IRAP, F-31028 Toulouse cedex 4, France and GAHEC, Université de Toulouse, UPS-OMP, IRAP, 31028 Toulouse, France.
³⁷ Department of Physics, Stockholm University, AlbaNova, SE-106 91 Stockholm, Sweden and The Oskar Klein Centre for Cosmoparticle Physics, AlbaNova, SE-106 91 Stockholm, Sweden and Department of Astronomy, Stockholm University, SE-106 91 Stockholm, Sweden.
³⁸ Istituto Nazionale di Fisica Nucleare, Sezione di Torino, I-10125 Torino, Italy.
³⁹ NASA Goddard Space Flight Center, Greenbelt, Maryland 20771, USA and Department of Physics and Department of Astronomy, University of Maryland, College Park, Maryland 20742, USA.
⁴⁰ W. W. Hansen Experimental Physics Laboratory, Kavli Institute for Particle Astrophysics and Cosmology, Department of Physics and SLAC National Accelerator Laboratory, Stanford University, Stanford, California 94305, USA and Department of Physics, Faculty of Science, Mahidol University, Bangkok 10400, Thailand.
⁴¹ Hiroshima Astrophysical Science Center, Hiroshima University, Higashi-Hiroshima, Hiroshima 739-8526, Japan.
⁴² Department of Physics and Department of Astronomy, University of Maryland, College Park, Maryland 20742, USA and Center for Research and Exploration in Space Science and Technology (CRESST) and NASA Goddard Space Flight Center, Greenbelt, Maryland 20771, USA.
⁴³ Istituto Nazionale di Fisica Nucleare, Sezione di Roma "Tor Vergata", I-00133 Roma, Italy.
⁴⁴ Center for Cosmology, Physics and Astronomy Department, University of California, Irvine, California 92697-2575, USA.
⁴⁵ NASA Goddard Space Flight Center, Greenbelt, Maryland 20771, USA and Center for Research and Exploration in Space Science and Technology (CRESST) and NASA Goddard Space Flight Center, Greenbelt, Maryland 20771, USA and Department of Physics and Center for Space Sciences and Technology, University of Maryland Baltimore County, Baltimore, Maryland 21250, USA.
⁴⁶ W. W. Hansen Experimental Physics Laboratory, Kavli Institute for Particle Astrophysics and Cosmology, Department of Physics and SLAC National Accelerator Laboratory, Stanford University, Stanford, California 94305, USA and Solar-Terrestrial Environment Laboratory, Nagoya University, Nagoya 464-8601, Japan.
⁴⁷ Department of Physics and Astronomy, University of Denver, Denver, Colorado 80208, USA.
⁴⁸ W. W. Hansen Experimental Physics Laboratory, Kavli Institute for Particle Astrophysics and Cosmology, Department of Physics and SLAC National Accelerator Laboratory, Stanford University, Stanford, California 94305, USA and Max-Planck-Institut für Physik, D-80805 München, Germany.
⁴⁹ Department of Physics, University of Johannesburg, PO Box 524, Auckland Park 2006, South Africa.
⁵⁰ W. W. Hansen Experimental Physics Laboratory, Kavli Institute for Particle Astrophysics and Cosmology, Department of Physics and SLAC National Accelerator Laboratory, Stanford University, Stanford, California 94305, USA and Institut für Astro- und Teilchenphysik and Institut für Theoretische Physik, Leopold-Franzens-Universität Innsbruck, A-6020 Innsbruck, Austria.
⁵¹ Department of Physics, University of Washington, Seattle, Washington 98195-1560, USA.
⁵² National Research Council Research Associate, National Academy of Sciences, Washington, D.C. 20001, USA.
⁵³ NYCB Real-Time Computing Inc., Lattingtown, New York 11560-1025, USA.
⁵⁴ Max-Planck Institut für extraterrestrische Physik, 85748 Garching, Germany.
⁵⁵ Research Institute for Science and Engineering, Waseda University, 3-4-1, Okubo, Shinjuku, Tokyo 169-8555, Japan.
⁵⁶ Institut de Ciències de l'Espai (IEEE-CSIC), Campus UAB, 08193 Barcelona, Spain and Institució Catalana de Recerca i Estudis Avançats (ICREA), Barcelona, Spain.
⁵⁷ Istituto Nazionale di Fisica Nucleare, Sezione di Roma "Tor Vergata", I-00133 Roma, Italy and Dipartimento di Fisica, Università di Roma "Tor Vergata", I-00133 Roma, Italy.
⁵⁸ Department of Physics, Stockholm University, AlbaNova, SE-106 91 Stockholm, Sweden and The Oskar Klein Centre for Cosmoparticle Physics, AlbaNova, SE-106 91 Stockholm, Sweden.

PMID: 24785023
DOI: 10.1103/PhysRevLett.112.151103

Abstract

Recent accurate measurements of cosmic-ray (CR) species by ATIC-2, CREAM, and PAMELA reveal an unexpected hardening in the proton and He spectra above a few hundred GeV, a gradual softening of the spectra just below a few hundred GeV, and a harder spectrum of He compared to that of protons. These newly discovered features may offer a clue to the origin of high-energy CRs. We use the Fermi Large Area Telescope observations of the γ-ray emission from Earth's limb for an indirect measurement of the local spectrum of CR protons in the energy range ∼90 GeV-6 TeV (derived from a photon energy range 15 GeV-1 TeV). Our analysis shows that single power law and broken power law spectra fit the data equally well and yield a proton spectrum with index 2.68±0.04 and 2.61±0.08 above ∼200 GeV, respectively.