High-Statistics Measurement of the Cosmic-Ray Electron Spectrum with H.E.S.S

Abstract

Owing to their rapid cooling rate and hence loss-limited propagation distance, cosmic-ray electrons and positrons (CRe) at very high energies probe local cosmic-ray accelerators and provide constraints on exotic production mechanisms such as annihilation of dark matter particles. We present a high-statistics measurement of the spectrum of CRe candidate events from 0.3 to 40 TeV with the High Energy Stereoscopic System (H.E.S.S.), covering two orders of magnitude in energy and reaching a proton rejection power of better than $10^4$. The measured spectrum is well described by a broken power law, with a break around 1 TeV, where the spectral index increases from ${\Gamma }_1=3.25$ $\pm$ 0.02 (stat) $\pm$ 0.2 (sys) to ${\Gamma }_2=4.49$ $\pm$ 0.04 (stat) $\pm$ 0.2 (sys). Apart from the break, the spectrum is featureless. The absence of distinct signatures at multi-TeV energies imposes constraints on the presence of nearby CRe accelerators and the local CRe propagation mechanisms.

main paper: 8 pages, 4 figures, supplemental material: 12 pages, 14 figures, accepted for publication in Physical Review Letters https://journals.aps.org/prl/

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• Universal energy limits of radiation belts in planetary and brown dwarf magnetospheric systems
• A New Census of the Universe's Entropy
• SECRET: Stochasticity Emulator for Cosmic Ray Electrons
• Anisotropic diffusion modeling of cosmic-ray lepton propagation