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

D. Grasso , S. Profumo , A.W. Strong , Luca Baldini , R. Bellazzini , E.D. Bloom , J. Bregeon , G. Di Bernardo , D. Gaggero , N. Giglietto , T. Kamae , L. Latronico , F. Longo , M.N. Mazziotta , A.A. Moiseev , A. Morselli , J.F. Ormes , M. Pesce-Rollins , M. Pohl , M. Razzano , C. Sgro , G. Spandre , T.E. Stephens

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. Here we discuss several interpretations of the Fermi results based either on a single large scale Galactic CRE component or by invoking additional electron-positron primary sources, e.g. nearby pulsars or particle Dark Matter annihilation. We show that while the reported Fermi-LAT data alone can be interpreted in terms of a single component scenario, when combined with other complementary experimental results, specifically the CRE spectrum measured by H.E.S.S. and especially the positron fraction reported by PAMELA between 1 and 100 GeV, that class of models fails to provide a consistent interpretation. Rather, we find that several combinations of parameters, involving both the pulsar and dark matter scenarios, allow a consistent description of those results. We also briefly discuss the possibility of discriminating between the pulsar and dark matter interpretations by looking for a possible anisotropy in the CRE flux.

Mots clés: Physical Sciences

D. Grasso, S. Profumo, A.W. Strong, Luca Baldini, R. Bellazzini, et al.. On possible interpretations of the high energy electron-positron spectrum measured by the Fermi Large Area Telescope. Astroparticle Physics, 2009, 32 (2), pp.140. ⟨10.1016/j.astropartphys.2009.07.003⟩. ⟨hal-00498975⟩