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High-energy cosmic-ray electrons and positrons (CREs), which lose energy quickly during their propagation, provide a probe of Galactic high-energy processes and may enable the observation of phenomena such as dark-matter particle annihilation or decay. The CRE spectrum has been measured directly up to approximately 2 teraelectronvolts in previous balloon- or space-borne experiments, and indirectly up to approximately 5 teraelectronvolts using ground-based Cherenkov γ-ray telescope arrays. Evidence for a spectral break in the teraelectronvolt energy range has been provided by indirect measurements, although the results were qualified by sizeable systematic uncertainties. Here we report a direct measurement of CREs in the energy range 25 gigaelectronvolts to 4.6 teraelectronvolts by the Dark Matter Particle Explorer (DAMPE) with unprecedentedly high energy resolution and low background. The largest part of the spectrum can be well fitted by a 'smoothly broken power-law' model rather than a single power-law model. The direct detection of a spectral break at about 0.9 teraelectronvolts confirms the evidence found by previous indirect measurements, clarifies the behaviour of the CRE spectrum at energies above 1 teraelectronvolt and sheds light on the physical origin of the sub-teraelectronvolt CREs.

Using the latest AMS-02 cosmic ray antiproton flux data, we search for potential dark matter annihilation signal. The background parameters about the propagation, source injection, and solar modulation are not assumed a priori, but based on the results inferred from the recent B/C ratio and proton data measurements instead. The possible dark matter signal is incorporated into the model self-consistently under a Bayesian framework. Compared with the astrophysical background only hypothesis, we find that a dark matter signal is favored. The rest mass of the dark matter particles is ∼ 20 − 80 GeV and the velocity-averaged hadronic annihilation cross section is about (0.2 − 5) × 10 −26 cm 3 s −1 , in agreement with that needed to account for the Galactic center GeV excess and/or the weak GeV emission from dwarf spheroidal galaxies Reticulum 2 and Tucana III. Tight constraints on the dark matter annihilation models are also set in a wide mass region. PACS numbers: 95.35.+d,Introduction -The precise measurements of cosmic ray (CR) anti-particle spectra by space-borne instruments, such as PAMELA and AMS-02, provide very good sensitivity to probe the particle dark matter (DM) annihilation or decay in the Milky Way. The CR antiprotons, primarily come from the inelastic collisions between the CR protons (and Helium) and the interstellar medium (ISM), are effective to constrain the DM models [1][2][3]. Recent observations of the antiproton fluxes [4][5][6] are largely consistent with the expectation from the CR propagation model, leaving very limited room for the annihilation or decay of DM [2,[7][8][9][10].There are several sources of uncertainties in using antiprotons to constrain DM models. The largest uncertainty may come from the propagation parameters. Usually the secondary-to-primary ratio of CR nuclei, such as the Boronto-Carbon ratio (B/C), and the radioactive-to-stable isotope ratio of secondary nuclei, such as the Beryllium isotope ratio 10 Be/ 9 Be, are used to determine the propagation parameters [11,12]. Limited by the data quality, the constraints on the propagation parameters are loose [13,14]. Even the effect on the background antiproton flux due to uncertainties of propagation parameters is moderate, the flux from the DM component depends sensitively on propagation parameters [15]. Additional uncertainties include the injection spectrum of the CR nuclei, solar modulation, and hadronic interaction models [8]. Those uncertainties make the DM searches with antiprotons inconclusive [16,17].Given the new measurements of the proton, Helium, and B/C data by , improved constraints on the propagation and source injection parameters can be obtained through global Bayesian approaches [22][23][24][25]. With these data, we conduct a global study to determine the propagation, injection, and solar modulation parameters si- * The corresponding author: yuanq@pmo.ac.cn † The corresponding author: yzfan@pmo.ac.cn multaneously using the Markov Chain Monte Carlo (MCMC) method [26]. These "background" parameters and their like...

The DArk Matter Particle Explorer (DAMPE), one of the four scientific space science missions within the framework of the Strategic Pioneer Program on Space Science of the Chinese Academy of Sciences, is a general purpose high energy cosmic-ray and gamma-ray observatory, which was successfully launched on December 17th, 2015 from the Jiuquan Satellite Launch Center. The DAMPE scientific objectives include the study of galactic cosmic rays up to $\sim 10$ TeV and hundreds of TeV for electrons/gammas and nuclei respectively, and the search for dark matter signatures in their spectra. In this paper we illustrate the layout of the DAMPE instrument, and discuss the results of beam tests and calibrations performed on ground. Finally we present the expected performance in space and give an overview of the mission key scientific goals.Comment: 45 pages, including 29 figures and 6 tables. Published in Astropart. Phy