Towards Understanding the Origin of Cosmic-Ray Electrons

Abstract

Precision results on cosmic-ray electrons, based on $28.1 \times 10^{6}$ electrons collected by the Alpha Magnetic Spectrometer on the International Space Station, are presented in the energy range from 0.5 GeV to 1.4 TeV. Compared to the positron spectrum, the electron spectrum has distinctly different magnitudes and energy dependences in the entire energy range. At low energy region, electron flux exhibits a significant excess starting from $42.1_{-5.2}^{+5.4}$ GeV compared to the lower energy trends, but the nature of this excess is different from the positron flux excess above $25.2 \pm 1.8$ GeV. At high energy region, it does not have an energy cutoff below 1.9 TeV at the 5$\sigma$ level, which is contrary to the positron flux with an exponential energy cutoff of $810_{-180}^{+310}$ GeV. In the entire energy range the electron flux is well described by the sum of two power law components. It's a clear evidence that most high energy electrons originate from different sources than high energy positrons, based on the different behavior of the cosmic-ray electrons and positrons measured by the Alpha Magnetic Spectrometer.