1. 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.
Found in: ključnih besedah
Keywords: dark matter, early universe
Published: 23.03.2016; Views: 3572; Downloads: 0
 Fulltext (431,48 KB) |
2. Indirect Detection ExperimentsGabrijela Zaharijas, 2017, published scientific conference contribution abstract (invited lecture) Found in: ključnih besedah
Summary of found: ...significant number of experiments actively monitoring high-energy Universe. Many of these probes provide excellent tests...
Keywords: We live in a golden age for astro-particle physics, with a significant number of experiments actively monitoring high-energy Universe. Many of these probes provide excellent tests of particle physics models of dark matter particles. In particular, experiments such as Fermi -LAT, AMS-02, Ice Cube, ... are significantly cutting into the parameter space of one of the most popular candidates, the WIMPs. In this talk I will describe some of the strategies and methods used to search for dark matter with astrophysical data. Special attention will be given to the latest indications of an unaccounted gamma-ray excess at few GeV in the Fermi-LAT data in the region around the Galactic Centre, which steered lots of attention as it was shown to be consistent with putative signals of WIMP dark matter particles and complementary constraints provided by other experiments. Finally I will discuss projections of the expected sensitivities with upcoming experiments and continued data taking with current ones.
Published: 17.07.2017; Views: 3975; Downloads: 0
Fulltext (50,35 MB) |
3. Search for Physics beyond the Standard Model with the CRESST Experiment2017, master's thesis Abstract: In spite of the successes of observational astro- and particle physics and cosmology very much of the universe remains unknown. The Standard Model of particle physics is a theory describing the electromagnetic, weak, and strong nuclear interactions, as well as classifying all the subatomic particles known. But there is overwhelming evidence, that all the known particles, the ordinary (baryonic) matter, the building blocks of planets, stars and ourselves, only make up about 4.9% of the energy content of the universe. The standard model of cosmology (CDM) indicates that the total mass-energy of the universe contains beside the 4.9% ordinary matter two other components: 26.8% dark matter and 68.3% dark energy. The accelerating expansion of the Universe is the result of the effect of the dark energy with its most simple form given by a cosmological constant in Einstein's Equation. Dark matter is an unidentified type of matter that is not accounted for by dark energy and neutrinos and is generally believed to be a non-relativistic, charge neutral and non-baryonic new form of matter. Although dark matter has not been directly observed yet, its existence and properties are inferred from its gravitational effects such as the motions of visible matter, gravitational lensing, its influence on the universe's large-scale structure, and its effects in the cosmic microwave background. Thus the search for Dark Matter is the search for physics beyond the standard model. Although the nature of dark matter is yet unknown, its presence is crucial to understanding the future of the universe. The CRESST experiment is searching for direct evidence in the form of a nuclear recoil induced on a scintillating CaWO4 crystal by a dark matter particle, and is installed and taking data underground at Laboratory Nazionali del Gran Sasso (LNGS) in Italy. While both, dark energy and dark matter, have not been detected directly, a class of dark matter particles that interact only via gravity and the weak force, referred to asWeakly Interacting Massive Particles (WIMPs), has been established as the leading candidate among the dark matter community. For this thesis a special model of dark matter was studied, namely the dark photon. This thesis provides a detailed description of the calculation of the 90% upper limit on the dark photon kinetic mixing based on data from the second phase of the CRESST experiment. The analysis was carried out in a frequentist approach based on the (unbinned) maximum-likelihood method and likelihood ratios. To make a statement about the calculated result and its quality, the used algorithm had to be tested, what was done with Monte Carlo simulations (pseudo data).
Found in: ključnih besedah
Summary of found: ...physics and cosmology very much of the universe remains unknown. The Standard Model of particle...
Keywords: astro physics, particle physics, cosmology, universe, Standard Model of particle physics, standard model of cosmology, matter, ordinary matter, dark matter, dark energy, accelerating expansion of the Universe, non-baryonic, new form of matter, gravitational lensing, cosmic microwave background, search for physics beyond the standard model, CRESST experiment, direct detection, CaWO4 crystal, underground laboratory, Laboratory Nazionali del Gran Sasso, Weakly Interacting Massive Particles, WIMP, dark photon, 90% upper limit, upper limit, kinetic mixing, frequentist approach, unbinned, maximum likelihood
Published: 13.10.2017; Views: 3627; Downloads: 0
Fulltext (10,71 MB) |
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7. Indications of Intermediate-Scale Anisotropy of Cosmic Rays with Energy Greater Than 57 EeV in the Northern Sky Measured with the Surface Detector of the Telescope Array ExperimentJ. P. Lundquist, R.U. Abbasi, 2014, original scientific article Abstract: We have searched for intermediate-scale anisotropy in the arrival directions of ultrahigh-energy cosmic rays with energies above 57 EeV in the northern sky using data collected over a 5 year period by the surface detector of the Telescope Array experiment. We report on a cluster of events that we call the hotspot, found by oversampling using 20∘-radius circles. The hotspot has a Li-Ma statistical significance of 5.1σ, and is centered at R.A.=146.7∘, Dec.=43.2∘. The position of the hotspot is about 19∘ off of the supergalactic plane. The probability of a cluster of events of 5.1σ significance, appearing by chance in an isotropic cosmic-ray sky, is estimated to be 3.7×10−4 (3.4σ).
Found in: ključnih besedah
Summary of found: ...of particles, cosmic rays, large-scale structure of universe, surveys...
Keywords: acceleration of particles, cosmic rays, large-scale structure of universe, surveys
Published: 24.04.2020; Views: 2231; Downloads: 0
Fulltext (529,81 KB) |
8. Evidence of Intermediate-scale Energy Spectrum Anisotropy of Cosmic Rays E ≥ 10^19.2 eV with the Telescope Array Surface DetectorJ. P. Lundquist, R.U. Abbasi, 2018, original scientific article Abstract: Evidence for an intermediate-scale energy spectrum anisotropy has been found in the arrival directions of ultra-high energy cosmic rays for energies greater than 10^19.2 eV in the northern hemisphere using 7 years of Telescope Array surface detector data. A relative energy distribution test is done comparing events inside oversampled spherical caps of equal exposure, to those outside, using the Poisson likelihood ratio. The center of maximum significance is at 9h16m, 45°, and has a deficit of events with energies 10^19.2 ≤ E < 10^19.75 eV and an excess for E ≥ 10^19.75 eV. The post-trial probability of this energy anisotropy, appearing by chance anywhere on an isotropic sky, is found by Monte Carlo simulation to be 9 × 10−5 (3.74σ global).
Found in: ključnih besedah
Keywords: astroparticle physics, cosmic rays, anisotropy, large-scale structure of universe
Published: 24.04.2020; Views: 2196; Downloads: 150
Fulltext (1,43 MB) |
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10. Evidence for a Supergalactic Structure of Magnetic Deflection Multiplets of Ultra-High Energy Cosmic RaysJ. P. Lundquist, R. Abbasi, 2020, original scientific article Abstract: Evidence for a large-scale supergalactic cosmic ray multiplet (arrival directions correlated with energy) structure is reported for ultra-high energy cosmic ray (UHECR) energies above 10^19 eV using seven years of data from the Telescope Array (TA) surface detector and updated to 10 years. Previous energy-position correlation studies have made assumptions regarding magnetic field shapes and strength, and UHECR composition. Here the assumption tested is that, since the supergalactic plane is a fit to the average matter density of the local Large Scale Structure (LSS), UHECR sources and intervening extragalactic magnetic fields are correlated with this plane. This supergalactic deflection hypothesis is tested by the entire field-of-view (FOV) behavior of the strength of intermediate-scale energy-angle correlations. These multiplets are measured in spherical cap section bins (wedges) of the FOV to account for coherent and random magnetic fields. The structure found is consistent with supergalactic deflection, the previously published energy spectrum anisotropy results of TA (the hotspot and coldspot), and toy-model simulations of a supergalactic magnetic sheet. The seven year data post-trial significance of this supergalactic structure of multiplets appearing by chance, on an isotropic sky, is found by Monte Carlo simulation to be 4.19σ. The ten years of data post-trial significance is 4.09σ. Furthermore, the starburst galaxy M82 is shown to be a possible source of the TA Hotspot, and an estimate of the supergalactic magnetic field using UHECR measurements is presented.
Found in: ključnih besedah
Keywords: astroparticle physics, cosmic rays, UHECR, supergalactic plane, multiplets, magnetic deflection, large-scale structure of universe
Published: 19.05.2020; Views: 1905; Downloads: 0
Fulltext (4,40 MB) |
