Direct Measurement of the Cosmic-Ray Proton Spectrum from 50 GeV to 10 TeV with the Calorimetric Electron Telescope on the International Space Station

O. Adriani, University of Florence, INFN Sezione di Florence
Y. Akaike, University of Maryland, Astroparticle Physics Laboratory, NASA/GSFC
K. Asano, Institute for Cosmic Ray Research, The University of Tokyo
Y. Asaoka, Waseda Research Institute for Science and Engineering, Waseda University, JEM Utilization Center, Human Spaceflight Technology Directorate, Japan Aerospace Exploration Agency
M. G. Bagliesi, University of Siena, INFN Sezione di Pisa
E. Berti, University of Florence, INFN Sezione di Florence
G. Bigongiari, University of Siena, INFN Sezione di Pisa
W. R. Binns, McDonnell Center for the Space Sciences, Washington University
S. Bonechi, University of Siena, INFN Sezione di Pisa
M. Bongi, University of Florence, INFN Sezione di Florence
P. Brogi, University of Siena, INFN Sezione di Pisa
A. Bruno, Heliospheric Physics Laboratory, NASA/GSFC
J. H. Buckley, McDonnell Center for the Space Sciences, Washington University
N. Cannady, Louisiana State University
G. Castellini, Institute of Applied Physics (IFAC), National Research Council (CNR), Via Madonna del Piano
C. Checchia, University of Padova, INFN Sezione di Padova
M. L. Cherry, Louisiana State University
G. Collazuol, University of Padova, INFN Sezione di Padova
V. Di Felice, University of Rome “Tor Vergata”, Via della Ricerca Scientifica, INFN Sezione di Rome
K. Ebisawa, Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency
H. Fuke, Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency
T. G. Guzik, Louisiana State University
T. Hams, University of Maryland, CRESST and Astroparticle Physics Laboratory NASA/GSFC
N. Hasebe, Waseda Research Institute for Science and Engineering, Waseda University
K. Hibino, Kanagawa University
M. Ichimura, Faculty of Science and Technology, Graduate School of Science and Technology, Hirosaki University
K. Ioka, Yukawa Institute for Theoretical Physics, Kyoto University
W. Ishizaki, Institute for Cosmic Ray Research, The University of Tokyo
M. H. Israel, McDonnell Center for the Space Sciences, Washington University
K. Kasahara, Waseda Research Institute for Science and Engineering, Waseda University
J. Kataoka, Waseda Research Institute for Science and Engineering, Waseda University
R. Kataoka, National Institute of Polar Research
Y. Katayose, Division of Intelligent Systems Engineering, Yokohama National University
C. Kato, Shinshu University
N. Kawanaka, Hakubi Center, Kyoto University
Y. Kawakubo, Louisiana State University, Aoyama Gakuin University
K. Kohri, Institute of Particle and Nuclear Studies, High Energy Accelerator Research Organization
H. S. Krawczynski, McDonnell Center for the Space Sciences, Washington University
J. F. Krizmanic, CRESST and Astroparticle Physics Laboratory NASA/GSFC, University of Maryland
T. Lomtadze, INFN Sezione di Pisa
P. Maestro, University of Siena, INFN Sezione di Pisa
P. S. Marrocchesi, University of Siena, INFN Sezione di Pisa
A. M. Messineo, University of Pisa, INFN Sezione di Pisa
J. W. Mitchell, Astroparticle Physics Laboratory, NASA/GSFC
S. Miyake, National Institute of Technology, Ibaraki College
A. A. Moiseev, University of Maryland, CRESST and Astroparticle Physics Laboratory NASA/GSFC
K. Mori, Waseda Research Institute for Science and Engineering, Waseda University, Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency
M. Mori, Ritsumeikan University
N. Mori, INFN Sezione di Florence
H. M. Motz, Global Center for Science and Engineering, Waseda University
K. Munakata, Shinshu University
H. Murakami, Waseda Research Institute for Science and Engineering, Waseda University
S. Nakahira, RIKEN
J. Nishimura, Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency
G. A. de Nolfo, Heliospheric Physics Laboratory, NASA/GSFC
S. Okuno, Kanagawa University
J. F. Ormes, University of DenverFollow
S. Ozawa, Waseda Research Institute for Science and Engineering, Waseda University
L. Pacini, University of Florence, Institute of Applied Physics (IFAC), National Research Council (CNR), Via Madonna del Piano, INFN Sezione di Florence
F. Palma, University of Rome “Tor Vergata”, Via della Ricerca Scientifica, INFN Sezione di Rome
P. Papini, INFN Sezione di Florence
A. V. Penacchioni, University of Siena, ASI Science Data Center (ASDC), Via del Politecnico snc
B. F. Rauch, McDonnell Center for the Space Sciences, Washington University
S. B. Ricciarini, Institute of Applied Physics (IFAC), National Research Council (CNR), Via Madonna del Piano, INFN Sezione di Florence
K. Sakai, CRESST and Astroparticle Physics Laboratory NASA/GSFC, University of Maryland
T. Sakamoto, Aoyama Gakuin University
M. Sasaki, CRESST and Astroparticle Physics Laboratory NASA/GSFC, University of Maryland
Y. Shimizu, Kanagawa University
A. Shiomi, Nihon University
R. Sparvoli, University of Rome “Tor Vergata”, Via della Ricerca Scientifica, INFN Sezione di Rome
P. Spillantini, University of Florence
F. Stolzi, University of Siena, INFN Sezione di Pisa
J. E. Suh, University of Siena, INFN Sezione di Pisa
A. Sulaj, University of Siena, INFN Sezione di Pisa
I. Takahashi, Kavli Institute for the Physics and Mathematics of the Universe, The University of Tokyo
M. Takayanagi, Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency
M. Takita, Institute for Cosmic Ray Research, The University of Tokyo
T. Tamura, Kanagawa University
T. Terasawa, RIKEN
H. Tomida, Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency
S. Torii, Waseda Research Institute for Science and Engineering, Waseda University
Y. Tsunesada, Osaka City University
Y. Uchihori, National Institutes for Quantum and Radiation Science and Technology
S. Ueno, Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency
E. Vannuccini, INFN Sezione di Florence
J. P. Wefel, Louisiana State University
K. Yamaoka, Nagoya University
S. Yanagita, Ibaraki University
A. Yoshida, Aoyama Gakuin University
K. Yoshida, Shibaura Institute of Technology
CALET Collaboration

Publication Date

5-10-2019

Document Type

Article

Organizational Units

Physics and Astronomy

Keywords

Cosmic ray acceleration, Cosmic ray composition & spectra, Cosmic ray propagation, Cosmic ray sources, Cosmic rays & astroparticles

Abstract

In this paper, we present the analysis and results of a direct measurement of the cosmic-ray proton spectrum with the CALET instrument onboard the International Space Station, including the detailed assessment of systematic uncertainties. The observation period used in this analysis is from October 13, 2015 to August 31, 2018 (1054 days). We have achieved the very wide energy range necessary to carry out measurements of the spectrum from 50 GeV to 10 TeV covering, for the first time in space, with a single instrument the whole energy interval previously investigated in most cases in separate subranges by magnetic spectrometers (BESS-TeV, PAMELA, and AMS-02) and calorimetric instruments (ATIC, CREAM, and NUCLEON). The observed spectrum is consistent with AMS-02 but extends to nearly an order of magnitude higher energy, showing a very smooth transition of the power-law spectral index from −2.81±0.03 (50–500 GeV) neglecting solar modulation effects (or −2.87±0.06 including solar modulation effects in the lower energy region) to −2.56±0.04 (1–10 TeV), thereby confirming the existence of spectral hardening and providing evidence of a deviation from a single power law by more than 3σ.

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