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

TL;DR

This paper reports the first direct measurement of cosmic-ray electrons and positrons up to 4.6 TeV, revealing a spectral break at around 0.9 TeV, which confirms previous indirect evidence and advances understanding of high-energy Galactic processes.

Contribution

It provides the first direct measurement of the CRE spectrum up to 4.6 TeV with high resolution, confirming a spectral break at 0.9 TeV and improving understanding of cosmic-ray origins.

Findings

Detection of a spectral break at ~0.9 TeV in CRE spectrum

Confirmation of previous indirect measurements by H.E.S.S.

High energy resolution measurement up to 4.6 TeV

Abstract

High energy cosmic ray electrons plus positrons (CREs), which lose energy quickly during their propagation, provide an ideal 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 directly measured up to $\sim 2$ TeV in previous balloon- or space-borne experiments, and indirectly up to $\sim 5$ TeV by ground-based Cherenkov $\gamma$-ray telescope arrays. Evidence for a spectral break in the TeV energy range has been provided by indirect measurements of H.E.S.S., although the results were qualified by sizeable systematic uncertainties. Here we report a direct measurement of CREs in the energy range $25~{\rm GeV}-4.6~{\rm TeV}$ by the DArk Matter Particle Explorer (DAMPE) with unprecedentedly high energy resolution and low background. The majority of the spectrum can be properly fitted by a smoothly broken power-law model rather than a single power-law model. The direct detection of a spectral break at $E \sim0.9$ TeV confirms the evidence found by H.E.S.S., clarifies the behavior of the CRE spectrum at energies above 1 TeV and sheds light on the physical origin of the sub-TeV CREs.