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. 2019 Sep 27;5(9):eaax3793.
doi: 10.1126/sciadv.aax3793. eCollection 2019 Sep.

Measurement of the cosmic ray proton spectrum from 40 GeV to 100 TeV with the DAMPE satellite

DAMPE Collaboration; Q An  1   2 , R Asfandiyarov  3 , P Azzarello  3 , P Bernardini  4   5 , X J Bi  6   7 , M S Cai  8   9 , J Chang  8   9 , D Y Chen  7   8 , H F Chen  1   2 , J L Chen  10 , W Chen  7   8 , M Y Cui  8 , T S Cui  11 , H T Dai  1   2 , A D'Amone  4   5 , A De Benedittis  4   5 , I De Mitri  12   13 , M Di Santo  4   5 , M Ding  7   10 , T K Dong  8 , Y F Dong  6 , Z X Dong  11 , G Donvito  14 , D Droz  3 , J L Duan  10 , K K Duan  7   8 , D D'Urso  15 , R R Fan  6 , Y Z Fan  8   9 , F Fang  10 , C Q Feng  1   2 , L Feng  8 , P Fusco  14   16 , V Gallo  3 , F J Gan  1   2 , M Gao  6 , F Gargano  14 , K Gong  6 , Y Z Gong  8 , D Y Guo  6 , J H Guo  8   9 , X L Guo  8   9 , S X Han  11 , Y M Hu  8 , G S Huang  1   2 , X Y Huang  8 , Y Y Huang  8 , M Ionica  15 , W Jiang  8   9 , X Jin  1   2 , J Kong  10 , S J Lei  8 , S Li  7   8 , W L Li  11 , X Li  8 , X Q Li  11 , Y Li  10 , Y F Liang  8 , Y M Liang  11 , N H Liao  8 , C M Liu  1   2 , H Liu  8 , J Liu  10 , S B Liu  1   2 , W Q Liu  10 , Y Liu  8 , F Loparco  14   16 , C N Luo  8   9 , M Ma  11 , P X Ma  8   9 , S Y Ma  1   2 , T Ma  8 , X Y Ma  11 , G Marsella  4   5 , M N Mazziotta  14 , D Mo  10 , X Y Niu  10 , X Pan  8   9 , W X Peng  6 , X Y Peng  8 , R Qiao  6 , J N Rao  11 , M M Salinas  3 , G Z Shang  11 , W H Shen  11 , Z Q Shen  7   8 , Z T Shen  1   2 , J X Song  11 , H Su  10 , M Su  8   17 , Z Y Sun  10 , A Surdo  5 , X J Teng  11 , A Tykhonov  3 , S Vitillo  3 , C Wang  1   2 , H Wang  11 , H Y Wang  6 , J Z Wang  6 , L G Wang  11 , Q Wang  1   2 , S Wang  7   8 , X H Wang  10 , X L Wang  1   2 , Y F Wang  1   2 , Y P Wang  7   8 , Y Z Wang  7   8 , Z M Wang  12   13 , D M Wei  8   9 , J J Wei  8 , Y F Wei  1   2 , S C Wen  1   2 , D Wu  6 , J Wu  8   9 , L B Wu  1   2 , S S Wu  11 , X Wu  3 , K Xi  10 , Z Q Xia  8   9 , H T Xu  11 , Z H Xu  8   9 , Z L Xu  8 , Z Z Xu  1   2 , G F Xue  11 , H B Yang  10 , P Yang  10 , Y Q Yang  10 , Z L Yang  10 , H J Yao  10 , Y H Yu  10 , Q Yuan  8   9 , C Yue  7   8 , J J Zang  8 , F Zhang  6 , J Y Zhang  6 , J Z Zhang  10 , P F Zhang  8 , S X Zhang  10 , W Z Zhang  11 , Y Zhang  7   8 , Y J Zhang  10 , Y L Zhang  1   2 , Y P Zhang  10 , Y Q Zhang  7   8 , Z Zhang  8 , Z Y Zhang  1   2 , H Zhao  6 , H Y Zhao  10 , X F Zhao  11 , C Y Zhou  11 , Y Zhou  10 , X Zhu  1   2 , Y Zhu  11 , S Zimmer  3
Affiliations

Measurement of the cosmic ray proton spectrum from 40 GeV to 100 TeV with the DAMPE satellite

DAMPE Collaboration et al. Sci Adv. .

Abstract

The precise measurement of the spectrum of protons, the most abundant component of the cosmic radiation, is necessary to understand the source and acceleration of cosmic rays in the Milky Way. This work reports the measurement of the cosmic ray proton fluxes with kinetic energies from 40 GeV to 100 TeV, with 2 1/2 years of data recorded by the DArk Matter Particle Explorer (DAMPE). This is the first time that an experiment directly measures the cosmic ray protons up to ~100 TeV with high statistics. The measured spectrum confirms the spectral hardening at ~300 GeV found by previous experiments and reveals a softening at ~13.6 TeV, with the spectral index changing from ~2.60 to ~2.85. Our result suggests the existence of a new spectral feature of cosmic rays at energies lower than the so-called knee and sheds new light on the origin of Galactic cosmic rays.

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Figures

Fig. 1
Fig. 1. The combined signal spectra of PSD for protons and helium nuclei.
The left panel is for BGO deposited energies between 447 and 562 GeV, the middle panel is for BGO deposited energies of 4.47 to 5.62 TeV, and the right panel is for BGO deposited energies between 20 and 63 TeV. The on-orbit data (black) are shown, together with the best-fit templates of simulations of protons (blue), helium nuclei (green), and their sum (red). The vertical dashed lines show the cuts to select proton candidates in this deposited energy range.
Fig. 2
Fig. 2. Proton spectrum from 40 GeV to 100 TeV measured with DAMPE (red filled circles).
The red error bars show the statistical uncertainties, the inner shaded band shows the estimated systematic uncertainties due to the analysis procedure, and the outer band shows the total systematic uncertainties including also those from the hadronic models. The other direct measurements by PAMELA (10) (green stars), AMS-02 (11) (blue squares), ATIC-2 (7) (cyan diamonds), CREAM I + III (16) (magenta circles), and NUCLEON-KLEM (17) are shown for comparison. For the PAMELA data, a −3.2% correction of the absolute fluxes has been included (43, 44). The error bars of PAMELA and AMS-02 data include both statistical and systematic uncertainties added in quadrature. For ATIC-2, CREAM, and NUCLEON data, only statistical uncertainties are shown.
Fig. 3
Fig. 3. Some key information for the proton spectrum measurement.
(A) The charge selection efficiency of protons versus incident energies for the GEANT FTFP_BERT model. (B) The fraction of helium (red open circles) and electron (blue filled dots) backgrounds in the proton candidate events as a function of deposited energy. (C) Probability distribution of deposited energies in the BGO calorimeter for different incident energies, for the GEANT FTFP_BERT model. The color represents the fraction of events in each energy bin. (D) Effective acceptance of protons versus incident energies for the GEANT FTFP_BERT model.
Fig. 4
Fig. 4. Statistical and systematic uncertainties of the proton flux measurements.
Fig. 5
Fig. 5. Comparison between the best fitting of the proton spectrum from 1 to 100 TeV with the SBPL function (solid line) and the DAMPE data.
See this image and copyright information in PMC

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