Direct detection of a break in the teraelectronvolt cosmic-ray spectrum of electrons and positrons

A direct measurement of cosmic-ray electrons and positrons with unprecedentedly high energy resolution reveals a spectral break at about 0.9 teraelectronvolts, confirming the evidence found by previous indirect measurements. A break in the cosmic-ray spectrum The spectrum of cosmic-ray electrons and positrons that arrive at Earth potentially contains information about the sources that accelerated them, and may reveal dark-matter annihilation. The spectrum has previously been measured directly up to around 2 teraelectronvolts (TeV), and indirectly up to around 5 TeV from ground-based Cherenkov arrays, which revealed a possible break in the spectrum. The Dark Matter Particle Explorer (DAMPE) Collaboration reports a direct measurement between 25 gigaelectronvolts and 4.6 TeV, which clearly reveals a spectral break at around 0.9 TeV. High-energy cosmic-ray electrons and positrons (CREs), which lose energy quickly during their propagation, provide a probe of Galactic high-energy processes 1 , 2 , 3 , 4 , 5 , 6 , 7 and may enable the observation of phenomena such as dark-matter particle annihilation or decay 8 , 9 , 10 . The CRE spectrum has been measured directly up to approximately 2 teraelectronvolts in previous balloon- or space-borne experiments 11 , 12 , 13 , 14 , 15 , 16 , and indirectly up to approximately 5 teraelectronvolts using ground-based Cherenkov γ-ray telescope arrays 17 , 18 . Evidence for a spectral break in the teraelectronvolt energy range has been provided by indirect measurements 17 , 18 , 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) 19 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 17 , 18 , clarifies the behaviour of the CRE spectrum at energies above 1 teraelectronvolt and sheds light on the physical origin of the sub-teraelectronvolt CREs.