Distinctive properties of cosmic-ray positron and electron fluxes measured by AMS on ISS

Abstract

The precise AMS data reveals distinctive properties of cosmic-ray positron and electron fluxes. The positron spectrum hardens starting from ∼20 GeV. Most importantly, the positron spectrum exhibits a sharp drop-off at ∼300 GeV, showing the existence of an energy cutoff at highest energy. The electron spectrum is distinctly different from the positron spectrum in both the magnitude and energy dependence. The electron spectrum hardens from ∼30 GeV. Remarkably, the electron spectrum is well described by a single power law from 55 GeV to 1 TeV and does not have an energy cutoff. These experimental data show that, at high energies, the cosmic-ray positrons predominately originate either from dark matter annihilation or from a new astrophysical source, whereas the cosmic-ray electrons originate from different sources.