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Constraints on cosmological dark matter annihilation from the Fermi-LAT isotropic diffuse gamma-ray measurement
Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
2010 (English)In: Journal of Cosmology and Astroparticle Physics, ISSN 1475-7516, no 4, 014- p.Article in journal (Refereed) Published
Abstract [en]

The first published Fermi large area telescope (Fermi-LAT) measurement of the isotropic diffuse gamma-ray emission is in good agreement with a single power law, and is not showing any signature of a dominant contribution from dark matter sources in the energy range from 20 to 100 GeV. We use the absolute size and spectral shape of this measured flux to derive cross section limits on three types of generic dark matter candidates: annihilat- ing into quarks, charged leptons and monochromatic photons. Predicted gamma-ray fluxes from annihilating dark matter are strongly aected by the underlying distribution of dark matter, and by using different available results of matter structure formation we assess these uncertainties. We also quantify how the dark matter constraints depend on the assumed conventional backgrounds and on the Universe’s transparency to high-energy gamma-rays. In reasonable background and dark matter structure scenarios (but not in all scenarios we consider) it is possible to exclude models proposed to explain the excess of electrons and positrons measured by the Fermi-LAT and PAMELA experiments. Derived limits also start to probe cross sections expected from thermally produced relics (e.g. in minimal supersym- metry models) annihilating predominantly into quarks. For the monochromatic gamma-ray signature, the current measurement constrains only dark matter scenarios with very strong signals.

Place, publisher, year, edition, pages
2010. no 4, 014- p.
Keyword [en]
dark matter experiments, dark matter simulations, dark matter theory
National Category
Physical Sciences Astronomy, Astrophysics and Cosmology
URN: urn:nbn:se:su:diva-38905DOI: 10.1088/1475-7516/2010/04/014ISI: 000277684600019OAI: diva2:317448
Totalt 149 författare.Available from: 2010-05-03 Created: 2010-05-03 Last updated: 2012-04-27Bibliographically approved
In thesis
1. Cosmological Dark Matter and the Isotropic Gamma-Ray Background: Measurements and Upper Limits
Open this publication in new window or tab >>Cosmological Dark Matter and the Isotropic Gamma-Ray Background: Measurements and Upper Limits
2010 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis addresses the isotropic diffuse gamma-ray background, as measured by the Fermi gamma ray space telescope, and its implications for indirect detection of dark matter. We describe the measurement of the isotropic background, including also an alternative analysis method besides the one published by the Fermi-LAT collaboration. The measured isotropic diffuse background is compatible with a power law differential energy spectrum with a spectral index of  -2.41 ± 0.05 and -2.39 ± 0.08, for the two analysis methods respectively. This is a softer spectrum than previously reported by the EGRET experiment. This rules out any dominant contribution with a significantly different shape, e.g. from dark matter, in the energy range 20 MeV to 102.4 GeV. Instead we present upper limits on a signal originating from annihilating dark matter of extragalactic origin. The uncertainty in the dark matter signal is primarily dependent on the cosmological evolution of the dark matter distribution. We use recent N-body simulations of structure formation, as well as a semi-analytical calculation, to assess this uncertainty. We investigate three main annihilation channels and find that in some, but not in all, of our scenarios we can start to probe, and sometimes rule out, interesting parameter spaces of particle physics models beyond the standard model.We also investigate the possibility to use the angular anisotropies of the annihilation signal to separate it from a background originating from conventional sources, e.g. from active galactic nuclei. By carefully modelling the performance of the Fermi gamma-ray space telescope and galactic foregrounds we find that this method could be as sensitive as using information from the energy spectrum only.

Place, publisher, year, edition, pages
Stockholm: Department of Physics, Stockholm University, 2010. 118 p.
dark matter theory, dark matter simulations, dark matter experiments, isotropic gamma-ray background, Fermi gamma-ray space telescope
National Category
Subatomic Physics
Research subject
Theoretical Physics
urn:nbn:se:su:diva-38900 (URN)978-91-7447-082-6 (ISBN)
Public defence
2010-06-03, FD5, AlbaNova universitetscentrum, Roslagstullsbacken 21, Stockholm, 13:00 (English)

At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 4: Manuscript.

Available from: 2010-05-11 Created: 2010-05-03 Last updated: 2013-01-22Bibliographically approved

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Conrad, JanSellerholm, Alexander
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