On discrepancy between ATIC and Fermi data

Abstract

Either ATIC or Fermi-LAT data can be fitted together with the PAMELA data by three components: primary background ∼ E−3.3, secondary background ∼ E−3.6, and an additional source of electrons ∼ E−γaExp(−E/Ecut). We find that the best fits for ATIC + PAMELA and for Fermi + PAMELA are approximately the same, γa ≈ 2 and Ecut ∼ 500 GeV. However, the ATIC data have a narrow bump between 300 GeV and 600 GeV which contradicts the smooth Fermi spectrum. An interpretation of the ATIC bump as well as the featureless Fermi spectrum in terms of dark matter models and pulsars is discussed.