Extended Measurement of the Cosmic-Ray Electron and Positron Spectrum from 11 GeV to 4.8 TeV with the Calorimetric Electron Telescope on the International Space Station

Abstract

Extended results on the cosmic-ray electron + positron spectrum from 11 GeV to 4.8 TeV are presented based on observations with the Calorimetric Electron Telescope (CALET) on the International Space Station utilizing the data up to November 2017. The analysis uses the full detector acceptance at high energies, approximately doubling the statistics compared to the previous result. CALET is an all-calorimetric instrument with a total thickness of 30 X_{0} at normal incidence and fine imaging capability, designed to achieve large proton rejection and excellent energy resolution well into the TeV energy region. The observed energy spectrum in the region below 1 TeV shows good agreement with Alpha Magnetic Spectrometer (AMS-02) data. In the energy region below ∼300 GeV, CALET's spectral index is found to be consistent with the AMS-02, Fermi Large Area Telescope (Fermi-LAT), and Dark Matter Particle Explorer (DAMPE), while from 300 to 600 GeV the spectrum is significantly softer than the spectra from the latter two experiments. The absolute flux of CALET is consistent with other experiments at around a few tens of GeV. However, it is lower than those of DAMPE and Fermi-LAT with the difference increasing up to several hundred GeV. The observed energy spectrum above ∼1 TeV suggests a flux suppression consistent within the errors with the results of DAMPE, while CALET does not observe any significant evidence for a narrow spectral feature in the energy region around 1.4 TeV. Our measured all-electron flux, including statistical errors and a detailed breakdown of the systematic errors, is tabulated in the Supplemental Material in order to allow more refined spectral analyses based on our data.

Cosmic ray models

“…Gamma-ray observations can be also used to compare the CR spectrum as function of Galactic Figure 12: Left panel: Cosmic ray electron plus positron energy spectrum measured by AMS-02 [193], Fermi-LAT [194], H.E.S.S. [195], DAMPE [196], and CALET [197]. Right panel: Comparison of the proton spectrum from Fig.…”

“…12, we show the combined electron plus positron flux F (E) multiplied with E 3 measured by AMS-02 [193], Fermi-LAT [194], H.E.S.S. [195], DAMPE [196], and CALET [197]. The spectrum E 3 F (E) has a peak at 10 GeV and is affected by solar modulations at energies E < ∼ 20 GeV, as one can see from the differences between the data of PAMELA and AMS-02 which measured the electron flux at different times, for more details see Ref.…”

Features in cosmic-ray lepton data unveil the properties of nearby cosmic accelerators

“…At even higher energies, H.E.S.S. [5,6], DAMPE [7] and CALET [8] measured the e − + e + spectrum up to 20 TeV and outlined a sharp softening at 1 TeV. Above that feature, the power-law spectrum extends with no clear sign of cutoff all the way up to the maximal detected energy.…”

A genetic algorithm for astroparticle physics studies

“…The CR positron flux measured by PAMELA [16] and AMS-02 [17,18] shows a significant excess above ∼30 GeV and a cutoff at ∼200 GeV. Moreover, the spectra of CR leptons with a softening behavior at ∼0.9 TeV have been measured by DAMPE [19] and HESS [20], and confirmed by CALET [21]. These exciting features have triggered models involving: (i) nearby sources [22]; (ii) pulsars [23][24][25][26][27][28]; or (iii) dark matter [29][30][31][32][33].…”