@article{4e359e4624bd4cdc8acd08c8ee414e91,
title = "Direct Measurement of the Cosmic-Ray Carbon and Oxygen Spectra from 10 GeV/ n to 2.2 TeV/ n with the Calorimetric Electron Telescope on the International Space Station",
abstract = "In this paper, we present the measurement of the energy spectra of carbon and oxygen in cosmic rays based on observations with the Calorimetric Electron Telescope on the International Space Station from October 2015 to October 2019. Analysis, including the detailed assessment of systematic uncertainties, and results are reported. The energy spectra are measured in kinetic energy per nucleon from 10 GeV/n to 2.2 TeV/n with an all-calorimetric instrument with a total thickness corresponding to 1.3 nuclear interaction length. The observed carbon and oxygen fluxes show a spectral index change of ∼0.15 around 200 GeV/n established with a significance >3σ. They have the same energy dependence with a constant C/O flux ratio 0.911±0.006 above 25 GeV/n. The spectral hardening is consistent with that measured by AMS-02, but the absolute normalization of the flux is about 27% lower, though in agreement with observations from previous experiments including the PAMELA spectrometer and the calorimetric balloon-borne experiment CREAM.",
author = "{(CALET Collaboration)} and O. Adriani and Y. Akaike and K. Asano and Y. Asaoka and Bagliesi, {M. G.} and E. Berti and G. Bigongiari and Binns, {W. R.} and M. Bongi and P. Brogi and A. Bruno and Buckley, {J. H.} and N. Cannady and G. Castellini and C. Checchia and Cherry, {M. L.} and G. Collazuol and K. Ebisawa and H. Fuke and S. Gonzi and Guzik, {T. G.} and T. Hams and K. Hibino and M. Ichimura and K. Ioka and W. Ishizaki and Israel, {M. H.} and K. Kasahara and J. Kataoka and R. Kataoka and Y. Katayose and C. Kato and N. Kawanaka and Y. Kawakubo and K. Kobayashi and K. Kohri and Krawczynski, {H. S.} and Krizmanic, {J. F.} and J. Link and P. Maestro and Marrocchesi, {P. S.} and Messineo, {A. M.} and Mitchell, {J. W.} and S. Miyake and Moiseev, {A. A.} and M. Mori and N. Mori and Motz, {H. M.} and K. Munakata and S. Nakahira",
note = "Funding Information: We gratefully acknowledge JAXA{\textquoteright}s contributions to the development of CALET and to the operations onboard the International Space Station. We also wish to express our sincere gratitude to Agenzia Spaziale Italiana (ASI) and NASA for their support of the CALET project. This work was supported in part by JSPS Grant-in-Aid for Scientific Research (S) No. 26220708 and No. 19H05608, JSPS Grant-in-Aid for Scientific Research (B) No. 17H02901, and by the MEXT-Supported Program for the Strategic Research Foundation at Private Universities (2011-2015) (No. S1101021) at Waseda University. The CALET effort in Italy is supported by ASI under agreement 2013-018-R.0 and its amendments. The CALET effort in the United States is supported by NASA through Grants No. NNX16AB99G, No. NNX16AC02G, and No. NNH14ZDA001N-APRA-0075. Publisher Copyright: {\textcopyright} 2020 us.",
year = "2020",
month = dec,
day = "18",
doi = "10.1103/PhysRevLett.125.251102",
language = "English",
volume = "125",
journal = "Physical Review Letters",
issn = "0031-9007",
publisher = "American Physical Society",
number = "25",
}