The Dark Matter Particle Explorer (DAMPE), also known as “WuKong”, which was launched into a Sun-synchronous orbit at an altitude of about 500 km on 17 December 2015. The primary mission of WuKong is to search dark matter signatures by precisely measuring the spectra of cosmic-ray electrons/ positrons and gamma-rays up to about 10 TeV.

In its first 530 days of on-orbit operation, WuKong has detected ~2.8 billions of high energy cosmic-ray events, including ~1.5 millions cosmic-ray electrons and positrons above 25 GeV. Based on these valuable datasets, the scientists of WuKong obtained the most precise measurement of cosmic-ray spectrum of electrons and positrons (see fig.1) in TeV energy range all over the world.

Figure: The red dashed line represents a smoothly broken power-law model that best fits the DAMPE data in the range 55 GeV to 2.63 TeV. Also shown are the direct measurements from the space-borne experiments AMS-0214 and Fermi-LAT16, and the indirect measurement by the H.E.S.S. Collaboration (the grey band represents its systematic errors apart from the approximately 15% energy scale uncertainty)17,18. The error bars (±1σ) of DAMPE, AMS-02 and Fermi-LAT include both systematic and statistical uncertainties added in quadrature.

Compared with previous results from other experiments, the electron and positron data from WuKong are characterized by unprecedentedly high energy resolution and low background contamination. This result explores a new observation window in TeV range for astrophysics. For the first time, WuKong has directly detected a spectral break at ~0.9 TeV, which indicates the typical acceleration mechanism of high energy cosmic-ray electrons and positions in the universe. The precise measurement of this spectral break is considerably important for clarification of the possible connection between the positron anomaly and the dark matter. The data from WuKong also hint the presence of spectral structure at ~1.4 TeV - a possible signal from nearby high energy cosmic-ray sources, e.g. pulsars or exotic physical process. Yet more data are required to explore this phenomenon.

This research work by DAMPE Collaboration has been published in Nature on Nov. 30.

For more details please see: https://www.nature.com/articles/nature24475.pdf or https://arxiv.org/abs/1711.10981.