41. |
42. |
43. Dark Matter search with the Fermi Large Area TelescopeGabrijela Zaharijas, unpublished invited conference lecture Abstract: High energy gamma-rays are one of the most promising tools to constrain or reveal the nature of dark matter. During the almost eight years of the Fermi satellite mission, the data from its Large Area Telescope (LAT) were used to set constraints on the dark matter cross section to various particle channels which now cut well into the theoretically motivated region of the parameter space. In this talk I will describe methods used to search for evidence of dark matter with the LAT, and review the status of the searches. Special attention will be given to the latest indications of the origin of the unaccounted gamma-ray excess at few GeV in the Fermi-LAT data in the region around the Galactic Center, which steered lots of attention as it was shown to be consistent with putative signals of WIMP dark matter particles. Finally I will discuss projections of the expected sensitivities with continued LAT data taking.
Keywords: dark matter, Fermi LAT experiment
Published in RUNG: 21.06.2016; Views: 4743; Downloads: 0
This document has many files! More... |
44. Sensitivity projections for dark matter searches with the Fermi large area telescopeGabrijela Zaharijas, Collaboration Fermi LAT, 2016, original scientific article Abstract: The nature of dark matter is a longstanding enigma of physics; it may consist of particles beyond the Standard Model that are still elusive to experiments. Among indirect searchtechniques, which look for stable products from the annihilation or decay of dark matter particles, or from axions coupling to high-energy photons, observations of the γ -ray sky have come to prominence over the last few years, because of the excellent sensitivity of the Large Area Telescope (LAT) on the Fermi Gamma-ray Space Telescope mission. The LAT energy range from 20 meV to above 300 GeV is particularly well suited for searching for products of the interactions of dark matter particles. In this report we describe methods used to search for evidence of dark matter with the LAT, and review the status of searches performed with up to six years of LAT data. We also discuss the factors that determine the sensitivities of these searches, including the magnitudes of the signals and the relevant backgrounds, considering both statistical and systematic uncertainties. We project the expected sensitivities of each search method for 10 and 15 years of LAT data taking. In particular, we find that the sensitivity of searches targeting dwarf galaxies, which provide the best limits currently, will improve faster than the square root of observing time. Current LAT limits for dwarf galaxies using six years of data reach the thermal relic level for masses up to 120 GeV for the bb ̄ annihilation channel for reasonable dark matter density profiles. With projected discoveries of additional dwarfs, these limits could extend to about 250 GeV. With as much as 15 years of LAT data these searches would be sensitive to dark matter annihilations at the thermal relic cross section for masses to greater than 400 GeV (200 GeV) in the bb ̄(τ+τ−) annihilation channels.
Keywords: dark matter, gamma rays
Published in RUNG: 20.06.2016; Views: 4614; Downloads: 0
This document has many files! More... |
45. Constraints on the Galactic Dark Matter signal from the Fermi-LAT measurement of the diffuse gamma-ray emissionGabrijela Zaharijas, 2012, published scientific conference contribution Abstract: We study diffuse gamma-ray emission at intermediate Galactic latitudes measured by the Fermi Large Area Telescope with the aim of searching for a signal from dark matter annihilation or decay. In the absence of a robust dark matter signal, constraints are presented. We set both, conservative dark matter limits requiring that the dark matter signal does not exceed the observed diffuse gamma-ray emission and limits derived based on modeling the foreground astrophysical diffuse emission. Uncertainties in several parameters which characterize conventional astrophysical emission are taken into account using a profile likelihood formalism. The resulting limits impact the range of particle masses over which dark matter thermal production in the early Universe is possible, and challenge the interpretation of the PAMELA/Fermi-LAT cosmic ray anomalies as annihilation of dark matter.
Keywords: gamma rays, Galactic diffuse emission, dark matter serach
Published in RUNG: 03.05.2016; Views: 4388; Downloads: 0
This document has many files! More... |
46. |
47. Asymmetric WIMP Dark Matter in the presence of DM/anti-DM OscillationsGabrijela Zaharijas, 2012, published scientific conference contribution abstract Abstract: The class of ‘Asymmetric Dark Matter’ scenarios relies on the existence of a primordial
particle/anti-particle asymmetry in the dark sector related to the baryon asymmetry as a
way to address the observed similarity between the baryonic and dark matter energy densities
today. Focusing on this framework we calculate the evolution of the dark matter relic
abundance in the presence of particle/anti-particle oscillations. We show how oscillations reopen
the parameter space of asymmetric dark matter models, in particular in the direction of
allowing large (WIMP-scale) DM masses. Finally, we constrain the parameter space in this
framework by applying up-to-date bounds from indirect detection signals on annihilating DM.
Keywords: dark matter, early universe
Published in RUNG: 23.03.2016; Views: 4555; Downloads: 0
This document has many files! More... |
48. Galactic Dark Matter signal and the Fermi-LAT measurement of the diffuse gamma-ray emissionGabrijela Zaharijas, published scientific conference contribution Abstract: We study diffuse gamma-ray emission at intermediate Galactic latitudes measured by the Fermi LAT with the aim of searching for a signal from dark matter annihilation or decay. In the absence of a robust dark matter signal, constraints are presented. We present and improve upon conservative dark matter limits obtained with no modeling of the foreground astrophysical diffuse emission. We do so, by taking into account uncertainties in several parameters which characterize conventional astrophysical emission and using a profile likelihood formalism. The resulting limits impact the range of particle masses over which dark matter thermal production in the early Universe is possible, and challenge the interpretation of the PAMELA/Fermi-LAT cosmic ray anomalies as annihilation of dark matter.
Keywords: Dark matter, high-energy gamma rays
Published in RUNG: 21.03.2016; Views: 4445; Downloads: 0
This document has many files! More... |
49. Prospects for Indirect Dark Matter Searches with the Cherenkov Telescope Array (CTA)John Carr, Gabrijela Zaharijas, 2015, published scientific conference contribution Abstract: The Cherenkov Telescope Array (CTA) will have a unique chance of discovery for a large range of masses in Weakly Interacting Massive Particles models of dark matter. The principal target for dark matter searches with CTA is the centre of the Galactic Halo. The best strategy is to perform CTA observations within a few degrees of the Galactic Centre, with the Galactic Centre itself and the most intense diffuse emission regions removed from the analysis. Assuming a cuspy dark matter density profile for the Milky Way, 500 hours of observations in this region provide sensitivities to and below the thermal cross-section of dark matter annihilations, for masses between a few hundred GeV and a few tens of TeV; therefore CTA will have a significant chance of discovery in some models. Since the dark matter density in the Milky Way is far from certain in the inner kpc region, other targets are also proposed for observation, like ultra-faint dwarf galaxies such as Segue 1 with 100 hours per year proposed. Beyond these two observational targets, further alternatives, such as Galactic dark clumps, will be considered closer to the actual date of CTA operations. Sensitivity predictions for dark matter searches are given on the various targets taking into account the latest instrument response functions expected for CTA together with a discussion on the systematic uncertainties from the backgrounds.
Keywords: dark matter, gamma-ray astronomy
Published in RUNG: 01.03.2016; Views: 4640; Downloads: 230
 Full text (724,07 KB) |
