On possible interpretations of the high energy electron-positron spectrum measured by the Fermi Large Area Telescope

Authors:
  • DGD. Grasso
    D. Grasso
  • SPS. Profumo
    S. Profumo
  • ASA. W. Strong
    A. W. Strong
  • LBL. Baldini
    L. Baldini
  • RBR. Bellazzini
    R. Bellazzini
  • EBE. D. Bloom
    E. D. Bloom
  • JBJ. Bregeon
    J. Bregeon
  • GBG. Di Bernardo
    G. Di Bernardo
  • DGD. Gaggero
    D. Gaggero
  • NGN. Giglietto
    N. Giglietto
  • TKT. Kamae
    T. Kamae
  • LLL. Latronico
    L. Latronico
Preprint
Publisher website
Google Scholar
Abstract
The Fermi-LAT experiment recently reported high precision measurements of the spectrum of cosmic-ray electrons-plus-positrons (CRE) between 20 GeV and 1 TeV. The spectrum shows no prominent spectral features, and is significantly harder than that inferred from several previous experiments. We show that the interpretation of the reported data, especially when combined with other experimental results, requires changes to the standard scenario of CRE origin and propagation. Here we discuss several interpretations of the Fermi results based either on conventional Galactic cosmic ray diffusive models or by invoking additional electron-positron primary sources, e.g. nearby pulsars or particle Dark Matter annihilation. When appropriate, we account for other complementary experimental results, specifically the upper limits on the CRE flux above 600 GeV reported by H.E.S.S. and the measurement of the positron fraction reported by PAMELA between 1 and 100 GeV, as well as gamma-ray data. We find that several combinations of parameters involving both the pulsar and dark matter scenarios allow a consistent interpretation of all data sets. We also briefly discuss the possibility of discriminating between those scenarios by looking for a possible anisotropy in the CRE flux.