Probing the ATIC peak in the cosmic-ray electron spectrum with H.E.S.S

TL;DR

This study measures the cosmic-ray electron spectrum with H.E.S.S., confirming the overall flux similar to ATIC but ruling out a sharp peak, and finds a steepening spectrum above 1 TeV, informing dark matter and astrophysical source models.

Contribution

First H.E.S.S. measurement of the electron spectrum above 340 GeV that challenges the ATIC peak interpretation and refines the spectral shape at high energies.

Findings

H.E.S.S. flux agrees with ATIC within errors

Excludes a pronounced peak in the electron spectrum

Spectral index of 3.0 with steepening above 1 TeV

Abstract

The measurement of an excess in the cosmic-ray electron spectrum between 300 and 800 GeV by the ATIC experiment has - together with the PAMELA detection of a rise in the positron fraction up to 100 GeV - motivated many interpretations in terms of dark matter scenarios; alternative explanations assume a nearby electron source like a pulsar or supernova remnant. Here we present a measurement of the cosmic-ray electron spectrum with H.E.S.S. starting at 340 GeV. While the overall electron flux measured by H.E.S.S. is consistent with the ATIC data within statistical and systematic errors, the H.E.S.S. data exclude a pronounced peak in the electron spectrum as suggested for interpretation by ATIC. The H.E.S.S. data follow a power-law spectrum with spectral index of 3.0 +- 0.1 (stat.) +- 0.3 (syst.), which steepens at about 1 TeV.