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

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. In this paper, 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. Finally, 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.

Authors:
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Publication Date:
Research Org.:
SLAC National Accelerator Lab., Menlo Park, CA (United States)
Sponsoring Org.:
USDOE
Contributing Org.:
Fermi LAT Collaboration
OSTI Identifier:
1357437
Grant/Contract Number:  
AC02-76SF00515
Resource Type:
Accepted Manuscript
Journal Name:
Astroparticle Physics
Additional Journal Information:
Journal Volume: 32; Journal Issue: 2; Journal ID: ISSN 0927-6505
Publisher:
Elsevier
Country of Publication:
United States
Language:
English
Subject:
79 ASTRONOMY AND ASTROPHYSICS; Cosmic ray electrons and positrons; Pulsars; Dark-matter; Fermi-LAT

Citation Formats

Grasso, D., Profumo, S., Strong, A. W., Baldini, L., Bellazzini, R., Bloom, E. D., Bregeon, J., Di Bernardo, G., Gaggero, D., Giglietto, N., Kamae, T., Latronico, L., Longo, F., Mazziotta, M. N., Moiseev, A. A., Morselli, A., Ormes, J. F., Pesce-Rollins, M., Pohl, M., Razzano, M., Sgro, C., Spandre, G., and Stephens, T. E. On possible interpretations of the high energy electron–positron spectrum measured by the Fermi Large Area Telescope. United States: N. p., 2009. Web. doi:10.1016/j.astropartphys.2009.07.003.
Grasso, D., Profumo, S., Strong, A. W., Baldini, L., Bellazzini, R., Bloom, E. D., Bregeon, J., Di Bernardo, G., Gaggero, D., Giglietto, N., Kamae, T., Latronico, L., Longo, F., Mazziotta, M. N., Moiseev, A. A., Morselli, A., Ormes, J. F., Pesce-Rollins, M., Pohl, M., Razzano, M., Sgro, C., Spandre, G., & Stephens, T. E. On possible interpretations of the high energy electron–positron spectrum measured by the Fermi Large Area Telescope. United States. doi:10.1016/j.astropartphys.2009.07.003.
Grasso, D., Profumo, S., Strong, A. W., Baldini, L., Bellazzini, R., Bloom, E. D., Bregeon, J., Di Bernardo, G., Gaggero, D., Giglietto, N., Kamae, T., Latronico, L., Longo, F., Mazziotta, M. N., Moiseev, A. A., Morselli, A., Ormes, J. F., Pesce-Rollins, M., Pohl, M., Razzano, M., Sgro, C., Spandre, G., and Stephens, T. E. Sat . "On possible interpretations of the high energy electron–positron spectrum measured by the Fermi Large Area Telescope". United States. doi:10.1016/j.astropartphys.2009.07.003. https://www.osti.gov/servlets/purl/1357437.
@article{osti_1357437,
title = {On possible interpretations of the high energy electron–positron spectrum measured by the Fermi Large Area Telescope},
author = {Grasso, D. and Profumo, S. and Strong, A. W. and Baldini, L. and Bellazzini, R. and Bloom, E. D. and Bregeon, J. and Di Bernardo, G. and Gaggero, D. and Giglietto, N. and Kamae, T. and Latronico, L. and Longo, F. and Mazziotta, M. N. and Moiseev, A. A. and Morselli, A. and Ormes, J. F. and Pesce-Rollins, M. and Pohl, M. and Razzano, M. and Sgro, C. and Spandre, G. and Stephens, T. E.},
abstractNote = {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. In this paper, 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. Finally, 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.},
doi = {10.1016/j.astropartphys.2009.07.003},
journal = {Astroparticle Physics},
number = 2,
volume = 32,
place = {United States},
year = {2009},
month = {7}
}

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