Dissertations / Theses on the topic 'Dark matter'
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1
Halovanic, Maria. "Dark Matter poems /." College Park, Md. : University of Maryland, 2003. http://hdl.handle.net/1903/110.
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Thesis (M.F.A.) -- University of Maryland, College Park, 2003.Thesis research directed by: Creative Writing. Title from t.p. of PDF. Includes bibliographical references. Published by UMI Dissertation Services, Ann Arbor, Mich. Also available in paper.
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Zukin, Phillip Gregory. "Dark matter dynamics." Thesis, Massachusetts Institute of Technology, 2012. http://hdl.handle.net/1721.1/77258.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Physics, 2012.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Cataloged from student-submitted PDF version of thesis.
Includes bibliographical references (p. 147-150).
N-body simulations have revealed a wealth of information about dark matter halos but their results are largely empirical. Here we attempt to shed light on simulation results by using a combination of analytic and numerical methods. First we generalize an analytic model of halo formation, known as Secondary Infall, to include the effects of tidal torque. Given this model we compare its predictions for halo profiles to simulation results and infer that angular momentum plays an important role in setting the structure of dark matter profiles at small radii. Next, we focus on explaining the origin of universality in halos. We find evidence that diffusion -- which can potentially lead to universality -- occurs during halo evolution and is partially sourced by external torques from large scale structure. This is surprising given that the halo is nonlinear and typically thought to be unaffected by neighboring structures. Last, we describe promising ways to analytically describe the evolution of nonlinear halos using a Fokker-Planck formalism.
by Phillip Gregory Zukin.
Ph.D.
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Williams, A. J. R. "Dark matter phenomenology." Thesis, Royal Holloway, University of London, 2013. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.591078.
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In this thesis we present some phenomenological investigations of freeze-in models of dark matter and also a numerical calculation of the particle flux produced by dark matter annihilations around a rotating black hole. Freeze-in is an alternative dark matter production mechanism in which an out of equilibrium very weakly coupled particle is produced in the early universe. We consider the Minimal Supersymmetric Standard Model (MSSM) extended by an additional singlet superfield feebly coupled to the other particles. This feeble coupling leads to a long lifetime for the next to lightest superpartner which can only decay via this coupling. The long lifetime of this decaying particles could lead to displaced vertices which provide a prominent signal for beyond the standard model physics. The phenomenology of the signals from this simple Feebly Interacting Massive Particle (AMP) model is investigated and compared to some experimental searches. The freeze-in mechanism may also constitute an alternative for generating the correct relic density for dark matter candidates whose predicted freeze-out abundance is too low due to a large total annihilation cross section. We show that although such a mechanism could explain why a dark matter candidate has the correct relic density, some candidates may still be ruled out because they would lead to a large gamma ray flux in dwarf spheroidal galaxies or a large elastic scattering rate in direct detection experiments. To investigate this scenario we examine neutralino dark matter in the MSSM. Collisions around black holes may provide a window onto very high energy physics. The geodesics of massless particles produced in collisions near a rotating black hole are solved numerically and a Monte Carlo integration of the momentum distribution of the massless particles is performed to calculate the fraction that escape the black hole to infinity. A distribution of in falling dark matter particles, which are assumed to annihilate to massless panicles, is considered and an estimate of the emergent flux from the collisions is made. The energy spectrum of the emergent particles is found to contain two Lorentz shifted peaks centred on the mass of the dark matter. The separation of the peaks is found to depend on the density profile of the dark matter and could provide information about the size of the annihilation plateau around a black hole and the mass of the dark matter particle.
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Panci, Tibaldo. "Dark matter phenomenology." Paris 7, 2011. http://www.theses.fr/2011PA077061.
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Dans cette thèse j'essaye de résumer la phénoménologie de la Matière Noire (MN) dans tous ses aspects: Détection Directe, Indirecte et constructions de modèles. Il s'agit d'un domaine très prometteur, car la profusion de mesures de ces dernières années l'a rapidement fait progresser et l'a rendu très dynamique. En ce qui concerne la Détection Directe je passe en revue les principaux ingrédients et recettes pour le calcul des signaux dus à une diffusion WIMP-noyau. Je présente le traitement analytique permettant de calculer le taux théorique attendu. Avec un choix standard des caractéristiques du halo de MN et de la section efficace d'interaction, je présente les régions favorisées actuelles et les contraintes sur la MN. En ce qui concerne la Détection Indirecte, je fournis les ingrédients les plus avancés pour calculer les signaux d'annihilations et désintégrations de MN à l'échelle du TeV. Avec ces ingrédients et recettes, je calcule les contraintes sur la MN qui sont imposées par le fond diffus gamma. Je considère les données de FERMI (1ere année) et je les compare aux prédictions d'annihilation et désintégration de MN. Enfin, comme les annihilations de MN après recombinaison et pendant l'époque de la formation des structures déposent de l'énergie dans le milieu intergalactique primordial, j’enquête également sur les contraintes imposées par la profondeur optique observée de l'Univers. En ce qui concerne la construction de modèles, je présente deux modèles jouets de MN qui peuvent échapper aux contraintes actuelles de détection directe. Ils sont fondés sur l'hypothèse que les forces entre les deux secteurs pourraient ne pas être à courte portéeIn this Ph. D. Thesis I have tried to summarize the Dark Matter (DM) phenomenology in ail aspects: Direct Detection, Indirect Detection and some aspects of mode! building. This is a very promising area as the profusion of ground and satellite-based measurements in recent years has rapidly advanced the field making it dynamic and timely. Concerning DM direct detection I review the main ingredients and recipes for Computing signals due to a WIMP-nucleus scattering I present the analytic treatment that allows us to derive the theoretical rate expected and, considering a standard choice in the features of the DM Halo and interaction cross section (point-like interaction), I report the current fits and constraints on DM properties. Concerning DM indirect detection, I provide the most advanced ingredients and recipes for Computing signals of TeV-scale DM annihilations and decays. Subsequently considering these ingredients and recipes, I compute the gamma ray constraints on DM properties that are imposed by the observed diffuse gamma rays. ] consider the data from FERMI first year observations and I compare them to the gamma rays fluxes predicted by DM annihilation and decays. Finally, as DM annihilations after recombination and during the epoch of structure formation deposit energy in the primordial intergalactic medium, I also investigate the constraints that are imposed by the observed optical depth of the Universe. Concerning model building, I present two DM toy mode 1s that can evade the current constraints on direct detection searches. They are based on the assumption that the forces between the two sectors might not be short range
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Baldi, Marco. "Interactions between Dark Energy and Dark Matter." Diss., lmu, 2009. http://nbn-resolving.de/urn:nbn:de:bvb:19-101617.
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Ciocia, Giuseppe. "Emerging dark matter from corpuscular dark energy." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2021. http://amslaurea.unibo.it/23294/.
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In the last years, the standard model of cosmology has been corroborated by a wide number of astrophysical observations. Despite its undeniable success, nowadays there is little knowledge about the true nature of dark matter and dark energy. In this thesis we use a different approach to give an intriguing answer to these open problems, in the light of the corpuscular model of gravity. We give a general overview on the reasons behind the need for a corpuscular theory of the gravitational interaction. Then, we show that if the same picture is extended to cosmological spaces, dark energy naturally emerges as a quantum state of the gravitational dynamics, and it is described as a Bose-Einstein condensate of very soft and virtual gravitons without the necessity of introducing an exotic dark fluid. Besides, the cosmic condensate responds locally to the presence of baryonic matter, and the back-reaction manifests itself in the emergence of a dark force that mimics a dark matter behavior. In particular, at galactic scales the MOND formula for the acceleration is recovered. Then, a first attempt of estimating the back-reaction is proposed within the framework of Bootstrapped Newtonian gravity, that allows for an effective field description where Newtonian theory is “bootstrapped" introducing post-Newtonian corrections, providing a useful tool for calculations. Finally, we show that a logarithmic potential arises as a solution of the Bootstrapped field equation, in accordance with MOND prediction.
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Mondragon, Antonio Richard. "Lorentz-violating dark matter." [College Station, Tex. : Texas A&M University, 2007. http://hdl.handle.net/1969.1/ETD-TAMU-1672.
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D'Eramo, Francesco. "Hot and dark matter." Thesis, Massachusetts Institute of Technology, 2012. http://hdl.handle.net/1721.1/76977.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Physics, 2012.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 253-273).
In this thesis, we build new Effective Field Theory tools to describe the propagation of energetic partons in hot and dense media, and we propose two new reactions for dark matter in the early universe. In the first part, we analyze the transverse momentum broadening in the absence of radiation of an energetic parton propagating through quark-gluon plasma via Soft Collinear Effective Theory (SCET). We show that the probability for picking up transverse momentum ki is given by the Fourier transform of the expectation value of two transversely separated light-like path-ordered Wilson lines. We evaluate the result for the strongly coupled plasma of N = 4 SYM theory by using gauge/gravity duality, and for the weakly coupled QCD plasma by using perturbation theory. In the second part, we introduce two new dark matter reactions, called "semi-annihilation" and "assimilation". The semi-annihilation reaction takes the schematic form [psi]i[psi]j -> [psi]k[psi], where [psi]i are stable dark matter particles and # is an unstable state. They lead to non-trivial dark matter dynamics in the early universe, and they might also take place today in the Milky Way, enriching the (semi-)annihilation final state spectrum observed in indirect detection experiments. The "assimilation" reaction efficiently destroy singlet dark matter particles, but dark matter number is stored in new quasi-stable heavy states which carry the baryon asymmetry. The subsequent annihilation and late-time decay of these heavy states yields (symmetric) dark matter as well as (asymmetric) standard model baryons.
by Francesco D'Eramo.
Ph.D.
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Mussie, Ezana. "Dark Matter, White Space." Thesis, Malmö universitet, Fakulteten för kultur och samhälle (KS), 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:mau:diva-21571.
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This thesis addresses the ambiguous role of Malmö’s latest megaproject in the context of the city’s racializing urban development trajectory. The project is a public/private congress center, concert hall and hotel complex called Malmö Live. Malmö Live is problematized as the height of spectacle and challenge as it is expected to be the city’s most prominent cultural and social meeting place. The inquiry is directed to how its expectation of relevancy came about and utilizes a Foucauldian inspired genealogical methodology. The result stems from an investigation of the historical, present, local and global conditions that constitutes the expectancy of its relevancy. The investigation notes the divisiveness of tourism and how it affects ways of thinking and doing government on multiple scales, and in particular how it motivates the case in question. The result shows that there are affinities between tourism- during-colonialism and the contemporary tourism industry. Where the former was appropriated by colonialism and overtly racializing, the latter is allowed appropriacy by a currency ascribed to selected geographies and histories. By describing the becoming of this megaproject and the use of tourism knowledge and technology, the how-question about the expectation of Malmö Live’s relevancy leads to a genealogical reconstruction of Malmö Live as a wager on whiteness. The wager on whiteness hold no guarantees, but the power of it is the ability to be persuasive and believed, and the currency it holds for those who perform it. The thesis ends with a discussion on what is at stake with Malmö Live, i.e. Malmö’s whiteness.
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McEwen, Joseph Eugene McEwen. "The Hidden Universe: Dark Energy, Dark Matter, Baryons." The Ohio State University, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=osu1471877488.
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Dienes, Keith R., Fei Huang, Shufang Su, and Brooks Thomas. "Dynamical Dark Matter from strongly-coupled dark sectors." AMER PHYSICAL SOC, 2017. http://hdl.handle.net/10150/623226.
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Dynamical Dark Matter (DDM) is an alternative framework for dark-matter physics in which the dark sector comprises a vast ensemble of particle species whose Standard-Model decay widths are balanced against their cosmological abundances. Previous studies of this framework have focused on a particular class of DDM ensembles-motivated primarily by Kaluza-Klein towers in theories with extra dimensions-in which the density of dark states scales roughly as a polynomial of the mass. In this paper, by contrast, we study the properties of a different class of DDM ensembles in which the density of dark states grows exponentially with mass. Ensembles with this Hagedorn-like property arise naturally as the "hadronic" resonances associated with the confining phase of a strongly-coupled dark sector; they also arise naturally as the gauge-neutral bulk states of Type I string theories. We study the dynamical properties of such ensembles, and demonstrate that an appropriate DDM-like balancing between decay widths and abundances can emerge naturally-even with an exponentially rising density of states. We also study the effective equations of state for such ensembles, and investigate some of the model-independent observational constraints on such ensembles that follow directly from these equations of state. In general, we find that such constraints tend to introduce correlations between various properties of these DDM ensembles such as their associated mass scales, lifetimes, and abundance distributions. For example, we find that these constraints allow DDM ensembles with energy scales ranging from the GeV scale all the way to the Planck scale, but that the total present-day cosmological abundance of the dark sector must be spread across an increasing number of different states in the ensemble as these energy scales are dialed from the Planck scale down to the GeV scale. Numerous other correlations and constraints are also discussed.
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Fornasa, Mattia. "Not-so-Dark Matter: strategies for indirect detection and identification of Dark Matter." Doctoral thesis, Università degli studi di Padova, 2009. http://hdl.handle.net/11577/3426089.
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The existence of Dark Matter (DM) is supported by multiple evidences, achieved by means of very different experimental strategies. Its energy density today has been measured to account for almost a quarter of the total energy density in the Universe.
DM is mainly sensible to gravity and it interacts only weakly through nuclear and electromagnetic interactions.
Under the assumption that a DM particle is its own anti-particle, annihilation products can be searched for in order to obtain informations about DM distribution and, more generally, to infer some of its properties. This is the idea beyond DM indirect detection. In this Ph.D. thesis I will focus only on DM annihilation into gamma-rays and discuss the possibility of obtaining clear DM signatures from the analysis of gamma-rays signals.
Being the annihilation flux proportional to the DM density squared, natural targets for indirect searches are the Galactic Center (due to its vicinity and its large amount of DM) and the near dwarf spheroidal galaxies (due to their large mass-to-light ratio). Experimental data from both these classes of sources have not found any clear DM signal, being able only to provide upper limits on the annihilation flux.
I will present here two alternative strategies for which DM signatures may be detected and a signal from annihilation may be disentagled from the gamma-ray background.
In the first case I will focus on the effect that Black Holes (BHs) can have on the distribution of DM producing overdensities. The most efficent mechanism is the adiabatic contraction around SuperMassive Black Holes, able to create large enhancements called spikes. However, the scenario of mini-spikes around Intermediate Mass Black Holes is more realistic and I will present prospects of detecting DM from mini-spikes in our Galaxy and in the Andromeda Galaxy.
I will move then to the analysis of the angular power spectrum of anistropies in the gamma-ray emission. After that the galactic foreground (due to cosmic rays interacting with the Galactic interstellar medium) is subtructed from a map of the gamma-ray sky, a residual isotropic background remains, called Extra-galactic Cosmic Gamma-ray Background (EGB) and measured by EGRET.
The Fermi LAT satellite will soon provide a more precise measurement of the EGB and I will present here predictions showing that the DM can contribution to the EGB flux and that its presence can be detected in the analysis of the angular power spectrum of the EGB. Both Galactic and extra-galactic DM substructures are taken into account, the first dominating the angular spectrum at low multipoles.
This thesis is based on the projects I have been involved in during my Ph.D. and I will mainly present results already discussed in those papers where I am among the authors.L'esistenza della Materia Oscura (MO) e' sostenuta da molteplici evidenze, ottenute con l'utilizzo di tecniche sperimentali diversificate e complementari. La densita' energetica della MO risulta spiegare quasi un quarto della densita' di energia dell'intero Universo. Essa risente prevalentemente della gravita' interagendo solo debolmente tramite interazioni nucleari ed elettromagnetiche. Seguendo l'ipotesi che la particella di MO sia anche la sua stessa anti-particella, una strategia per ottenere informazioni su come e' distribuita la MO e, piu' in generale per dedurre alcune delle sue proprieta', e' quella di cercare i suoi prodotti di annichilazione. E' questa l'idea che sta alla base della rivelazione indiretta di MO. Nella presente tesi di dottorato mi limitero' all'annichilazione della MO in raggi gamma e verranno discusse le previsioni per ottenere una chiara segnatura della presenza della MO dall'analisi dei segnali gamma. Essendo il flusso di annichilazione proporzionale alla densita' di MO al quadrato, gli obiettivi principali della rivelazione indiretta sono il Centro Galattico (a causa della sua vicinanza e della grande quantita' di MO stimata) e le galassie sferoidali nane presenti all'interno della Via Lattea (a causa del loro alto rapporto massa su luce). Gli dati sperimentali attuali provenienti da queste due classi di oggetti, non sono stati in grado di rivelare un chiaro segnale della presenza della MO, ma solamente di fornire dei limiti superiori al flusso di annichilazione. Presentero' in questa tesi due strategie alternative in grado di identificare delle segnature piuttosto chiare della presenza della MO attraverso le quali sara' possibile distinguere il segnale di annichilazione dal fondo gamma. Nel primo caso mi focalizzero' sull'effetto che i buchi neri possono avere sulla distribuzione di MO portando alla formazione di sovra-densita'. Il meccanismo piu' efficente e' quello della contrazione adiabatica attorno ai Buchi Neri SuperMassici, capace di produrre grandi innalzamenti nella densita' di MO chiamate cuspidi. D'altro canto, lo scenario piu' plausibile e' quello delle mini-cuspidi attorno ai Buchi Neri di Massa Intermedia e verranno presentate previsioni per la rivelazione della MO nelle mini-cuspidi della Via Lattea e della galassia di Andromeda. Mi focalizzero poi sulla seconda alternativa, lo studio dello spettro angolare di potenza per le anisotropie nell'emissione gamma. Dopo che il contributo Galattico (dovuto all'interazione dei raggi cosmici con il mezzo interstellare Galattico) e' stato sottratto dai dati di EGRET, un fondo isotropo residuo rimane, chiamato Fondo Extra-galattico Gamma (FEG). Il satellite Fermi LAT fornira' nell'immediato futuro una nuova stima del FEG ed io mostero', negli ultimi capitoli, come la MO possa contribuire al flusso del FEG e come la sua presenza possa essere rivelata nell'analisi del spettro angolare del FEG. Verranno considerate allo stesso tempo sottostrutture Galattiche ed extra-galattiche, dove le prime constituiscono la componente principale dello spettro angolare a bassi multipoli. Questa tesi e' basata sui progetti nei quali sono stato coinvolti durante il mio dottorato e presentero' risultati gia' discussi in quei lavori per i quali figuro tra gli autori.
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Ståhl, Martin. "Probing the effect of dark matter velocity distributions on neutrino-based dark matter detection." Thesis, Uppsala universitet, Högenergifysik, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-395645.
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Dark matter has a long history, but it was not until modern times that we have a chance of detecting it. This thesis focuses on the velocity distribution and its effect on indirect WIMP detection. Recently a new velocity distribution, based on data from SDSS and GAIA, was proposed. For this reason simulation of capture, annihilation and resulting flux of neutrinos from the Sun and Earth has been made both for the new and Maxwell-Boltzmann velocity distribution. The newly proposed velocity can reduce the annihilation rate in Earth by two thirds. For the Sun the effect depends on the mass of the WIMPs. For 50 GeV WIMPs the newly proposed velocity distribution could increase the annihilation rate by 5%, while for 3 TeV WIMPs it could decrease the annihilation rate by 28%. For Earth and high mass WIMPs the low velocity tail is the important part and the low resolution of this region in the new velocity distribution result in some uncertainties.
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Kranz, Thilo. "Dark matter in spiral galaxies." [S.l.] : [s.n.], 2002. http://deposit.ddb.de/cgi-bin/dokserv?idn=964708000.
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McCabe, Christopher. "Aspects of dark matter phenomenology." Thesis, University of Oxford, 2011. http://ora.ox.ac.uk/objects/uuid:74ec0d09-40d6-481d-b2ec-d0e9d41d5c1d.
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Identifying the relic particles that constitute the cold dark matter in our Universe is an outstanding problem in astro-particle physics. Direct detection experiments are among the most promising methods of detecting particle dark matter through non-gravitational interactions. In this thesis, the usual assumptions made when calculating the event rate at direct detection experiments are examined. Varying astrophysical parameters and the dark matter velocity distribution leads to significant changes in acceptance regions and exclusion curves for scenarios in which the tail of the velocity distribution is sampled; this includes 'light dark matter' (mass less than 10 GeV) and 'inelastic dark matter'. The DAMA and CoGeNT collaborations both report an annual modulation in their event rate that they attribute to dark matter. Two analyses of these experiments are performed. In the first, it is shown that these experiments can be compatible with each other and with the constraints from other direct detection experiments. This requires some isospin violation in the couplings of dark matter to protons and neutrons and a small inelastic splitting to boost the modulation fraction. The second analysis provides a comparison of the modulation signals free from all astrophysical parameters, under the assumption that dark matter scatters elastically. Again it is found that some isospin violation and a boosted modulation fraction is required in order that DAMA and CoGeNT are consistent with all experiments. A boosted modulation fraction may arise from a velocity distribution different from the Maxwell-Boltzmann distribution, which is usually assumed. Finally, a supersymmetric theory in which the dark matter candidate is a mixture of left- and right-handed sneutrino is considered. This theory has many novel signatures at colliders, indirect detection and direct detection experiments.
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Silverwood, Hamish George Miles. "Supersymmetric Dark Matter in IceCube." Thesis, University of Canterbury. Physics and Astronomy, 2012. http://hdl.handle.net/10092/6927.
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The Minimally Supersymmetric Standard Model (MSSM) provides us with a WIMP dark matter candidate particle, the neutralino. Neutralinos from the dark matter halo can potentially become captured by the sun and concentrated in the core, where they can undergo self-annihilation and so produce a distinct neutrino signal. The IceCube Neutrino Observatory has the potential to detect this neutrino signal and thus give indirect evidence of the presence and properties of neutralino dark matter. Although the full, unconstrained MSSM has 105 parameters this can be reduced to 25 parameters by the application of physically motivated assumptions. Scans of this MSSM-25 parameter space are conducted using the DarkSUSY software package and an adaptive scanning technique based on the Monte-Carlo VEGAS algorithm. The IceCube exclusion confidence level is then calculated for a set of points produced by these scans. Results indicate that the detection capability of IceCube exceeds that of current direct detection methods in certain regions of the parameter space. The use of a 25 dimensional parameter space reveals that there are new regions of observables with high exclusion confidence levels compared to earlier simulations performed with a seven dimensional parameter space.
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Macias, Ramirez Oscar. "Astrophysical Constraints on Dark Matter." Thesis, University of Canterbury. Department of Physics and Astronomy, 2014. http://hdl.handle.net/10092/9857.
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Well motivated theoretical models predict the annihilation of dark matter (DM) into standard model particles, a phenomenon which could be a significant source of photons in the gamma-ray sky. With its unprecedented sensitivity and its broad energy range (20 MeV to more than 300 GeV) the main instrument on board the Fermi satellite, the Large Area Telescope (LAT), might be able to detect an indirect signature of DM annihilations. In this work we revisit several interesting claims of extended dark matter emission made from analyses of Fermi-LAT data: First, based on three years of Fermi Large Area Telescope (LAT) gamma-ray data of the Virgo cluster, evidence for an extended emission associated with dark matter pair annihilation in the bb̄ channel has been reported by Han et al. (arxiv:1201.1003). After an in depth spatial and temporal analysis, we argue that the tentative evidence for a gamma-ray excess from the Virgo cluster is mainly due to the appearance of a population of previously unresolved gamma-ray point sources in the region of interest. These point sources are not part of the LAT second source catalogue (2FGL), but are found to be above the standard detection significance threshold when three or more years of LAT data is included.
Second, we confirm the detection of a spatially extended excess of 2-5 GeV gamma rays from the Galactic Center (GC), consistent with the emission expected from annihilating dark matter or an unresolved population of about 10³ milisecond pulsars. However, there are significant uncertainties in the diffuse galactic background at the GC. We have performed a revaluation of these two models for the extended gamma ray source at the GC by accounting for the systematic uncertainties of the Galactic diffuse emission model. We also marginalize over point source and diffuse background parameters in the region of interest. We show that the excess emission is significantly more extended than a point source. We find that the DM (or pulsars population) signal is larger than the systematic errors and therefore proceed to determine the sectors of parameter space that provide an acceptable fit to the data. We found that a population of order a 10³ MSPs with parameters consistent with the average spectral shape of Fermi-LAT measured MSPs was able to fit the GC excess emission. For DM, we found that a pure τ⁺τ⁻ annihilation channel is not a good fit to the data. But a mixture of τ⁻τ⁻ and bb̄ with a (σν) of order the thermal relic value and a DM mass of around 20 to 60 GeV provides an adequate fit.
We also consider the possibility that the GeV excess is due to nonthermal bremsstrahlung produced by a population of electrons interacting with neutral gas in molecular clouds. The millisecond pulsars and dark matter alternatives have spatial templates well fitted by the square of a generalized Navarro-Frenk-White (NFW) profile with inner slope γ = 1.2. We model the third option with a 20-cm continuum emission Galactic Ridge template. A template based on the HESS residuals is shown to give similar results. The gamma-ray excess is found to be best fit by a combination of the generalized NFW squared template and a Galactic Ridge template. We also find the spectra of each template is not significantly affected in the combined fit and is consistent with previous single template fits. That is, the generalized NFW squared spectrum can be fit by either of order 10³ unresolved MSPs or DM with mass around 30 GeV, a thermal cross section, and mainly annihilating to bb̄ quarks. While the Galactic Ridge continues to have a spectrum consistent with a population of nonthermal electrons whose spectrum also provides a good fit to synchrotron emission measurements. We also show that the current DM fit may be hard to test, even with 10 years of Fermi-LAT data, especially if there is a mixture of DM and MSPs contributing to the signal, in which case the implied DM cross section will be suppressed.
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Lin, Tongyan. "Signals of Particle Dark Matter." Thesis, Harvard University, 2012. http://dissertations.umi.com/gsas.harvard:10273.
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This thesis explores methods of detecting dark matter particles, with some emphasis on several dark matter models of current interest. Detection in this context means observation of an experimental signature correlated with dark matter interactions with Standard Model particles. This includes recoils of nuclei or electrons from dark matter scattering events, and direct or indirect observation of particles produced by dark matter annihilation.Physics
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McDowell, J. C. "Light limits on dark matter." Thesis, University of Cambridge, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.382578.
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Davis, Jonathan Henry Maynard. "The character of Dark Matter." Thesis, Durham University, 2014. http://etheses.dur.ac.uk/10672/.
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From galaxies, to clusters, to the Cosmic Microwave Background, there is strong gravitational evidence that the matter content of the Universe is not restricted to the particles of the Standard Model. Specifically, observations indicate that there must also be a large relic population of non-luminous Dark Matter. However, the character of this Dark Matter remains unknown: in particular, to what extent does it interact with the particles of the Standard Model, and with itself, through non-gravitational means? We seek to answer this question in this thesis. We first present constraints on the interaction of Dark Matter with quarks, through an analysis of data from the XENON100 and CoGeNT Direct Detection experiments. In order to do so, we develop a Bayesian technique, which aims to maximise the amount of information we can extract from the data. After this, we discuss potential constraints on the charge of Dark Matter due to its interactions with galactic magnetic fields, and the potential for constraints on its self-annihilation cross section from Cosmic Ray data. We also consider Dark Photons, which partner Dark Matter in many models, and place bounds on their couplings to quarks using the quark-gluon plasma, produced in heavy-ion collisions. We place emphasis on a multi-scale approach and on the robust statistical treatment of Dark Matter data. Our main scientific result comes from the analysis of CoGeNT data, where we show that there is less than one sigma evidence for DM recoils, in contrast to previous claims. We show that the ‘region of interest’ derived in previous analyses, is the result of a bias in the analysis from a particular choice of functional fit for the energy-dependence of the fraction of bulk events. When we account for this bias the preference for Dark Matter vanishes.
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Lopez, Honorez Laura. "Dark matter: signs and genesis." Doctoral thesis, Universite Libre de Bruxelles, 2007. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/210692.
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The success of Big Bang Nucleosynthesis (BBN) combined with the detailed analysis of the small imperfections of the Cosmic Microwave Background blackbody spectrum lead to the conclusion that most of the matter content of our universe is made of some non-baryonic material, the dark matter!
In this thesis, we review the compiling indications of dark matter and the so-called freeze-out mechanism which may settle the relic density of the species in the framework of the standard Big Bang model. We also examine principally two methods of detection of dark matter, direct and indirect detection searches.
Let us stress that the Standard Model on its own is unable to provide enough aspirants for the role of dark matter. As a consequence, one has to dig into the tremendous domain of physics "Beyond the Standard Model" in order to have a chance to elucidate the problem of the missing mass.
In this thesis in particular, we consider the Inert Doublet Model (IDM) which includes an additional Higgs doublet, enclosing two neutral scalars candidates for dark matter. We invoke the Standard freeze-out mechanism for the production of dark matter. We get then dark matter candidates in two rather separate mass ranges, one between 40 and 80 GeV, the other one between 400 GeV and 1 TeV. We also show that dark matter annihilation at the galactic center can be at the origin of a gamma-ray flux which can be probed by the future GLAST experiment.
We address a low reheating temperature scenario for the genesis of dark matter in a Left-Right symmetric extension of the Standard Model. The candidate for dark matter is a MeV right-handed neutrino and we show that a baryon-dark matter interaction at the galactic center can be the source of the low energy positrons responsible for the 511 keV gamma-ray excess observed by the INTEGRAL experiment in the galactic bulge region.
Finally, prompted by the possibility to explain the baryon and dark matter rather similar abundances by one single "Matter Genesis" mechanism, we study a non-thermal production mechanism for dark matter. The framework is also Left-Right symmetric and dark candidate is a ~3 GeV right handed neutrino.
Doctorat en Sciences
info:eu-repo/semantics/nonPublished
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Erkoca, Arif Emre. "Neutrino Signals from Dark Matter." Diss., The University of Arizona, 2010. http://hdl.handle.net/10150/195731.
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Large-scale neutrino telescopes will be powerful tools to observe multitude of mysterious phenomena happening in the Universe. The dark matter puzzle is listed as one of them. In this study, indirect detection of dark matter via neutrino signals is presented. The upward muon, the contained muon and the hadronic shower fluxes are calculated, assuming annihilation/decay of the dark matter in the core of the astrophysical objects and in the Galactic center. Direct neutrino production and secondary neutrino production from the decay of Standard Model particles produced in the annihilation/decay of dark matter are studied. The results are contrasted to the ones previously obtained in the literature, illustrating the importance of properly treating muon propagation and energy loss for the upward muon flux. The dependence of the dark matter signals on the density profile, the dark matter mass and the detector threshold are discussed. Different dark matter models (gravitino, Kaluza-Klein and leptophilic) which can account for recent observations of some indirect searches are analyzed regarding their detection in the kilometer size neutrino detectors in the near future. Muon and shower rates and the minimum observation times in order to reach 2σ detection significance are evaluated, with the result suggesting that the optimum cone half angles chosen about the Galactic center are about 10° (50°) for the muon (shower) events. A detailed analysis shows that for the annihilating dark matter models such as the leptophilic and Kaluza-Klein models, upward and contained muon as well as showers yield promising signals for dark matter detection in just a few years of observation, whereas for decaying dark matter models, the same observation times can only be reached with showers. The analytical results for the final fluxes are also obtained as well as parametric forms for the muon and shower fluxes for the dark matter models considered in this study.
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PRISCO, MAURIZIO. "Extra dimensions and dark matter." Doctoral thesis, Università degli Studi di Roma "Tor Vergata", 2008. http://hdl.handle.net/2108/607.
Full textAbstract:
In this thesis we analyze the consequences of extra spacetime dimensions
on the MSSM. We begin by reviewing the MSSM in four dimensions. We
specify the superpotential and all the possible soft terms to break supersymmetry.
After describing gravity-mediated susy breaking models, we present
the mass spectrum of the MSSM. In particular we introduce the neutralinos
as lightest supersymmetric particles. They are suitable candidates for
dark matter. We present a pedagogical introduction to the method of the
effective potential. We apply this method to the MSSM in order to obtain
its renormalization group equations. We also do an analysis in terms of
Feynman diagrams. We present the string-inspired model by Dienes, Dudas
and Gherghetta [Nuclear Physics B537, 47 (1999)]. We treat different scenarios
showing how extra dimensions give rise to `power-law' running of the
parameters. We also analyze the possible implications of extra dimensions
related to the dark matter problem. Extra dimensions affect also cosmology:
we take care of this modifying the Friedmann equation. The result of
the computation is that the neutralino is still the lightest supersymmetric
particle and it is higgsino like in most of the parameter space.
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Yegorova, Iryna. "Dark matter in spiral galaxies." Doctoral thesis, SISSA, 2007. http://hdl.handle.net/20.500.11767/4184.
Full textAbstract:
During the last few decades, it has been discovered that most of the material in the Universe is invisible. Since it interacts only gravitationally with the rest of the Universe components. From the latest measurements of WMAP satellite we know that the Universe consists of 4% Baryons, 22% Cold Dark Matter, 74% Dark Energy. Now it is clear a wonderful time to study cosmology. Using the latest technological advances we have obtained detailed picture of the early Universe and maps of the distribution of matter on the largest scales in the Universe today. And we have a physical model for the origin and evolution of the Universe. However on the small scales there are still a lot of open issues. The mass distribution in spiral galaxies is an interesting question that is tightly band to the galaxy formation and evolution process.
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Scott, Pat. "Searches for Particle Dark Matter Dark stars, dark galaxies, dark halos and global supersymmetric fits /." Doctoral thesis, Stockholm : Department of Physics, Stockholm University, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-38221.
Full textAbstract:
Diss. (sammanfattning) Stockholm : Stockholms universitet, 2010.At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 5: Accepted. Paper 6: Submitted. Härtill 6 uppsatser.
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Mitridate, Andrea. "Bindings in the dark : bound states in dark matter phenomenology." Doctoral thesis, Scuola Normale Superiore, 2019. http://hdl.handle.net/11384/85901.
Full textAbstract:
It is almost a century now since data implying the presence of nonluminous matter in the Universe surfaced: in 1932 Oort [1] observed that the number of stars near the sun was 30´50% less than the number necessary to explain their velocities; then, in 1933, Zwicky [2] pointed out that the velocity dispersion of galaxies in the Coma cluster required 10 to 100 times more mass than the one accounted for the luminous galaxies themselves. The same Zwicky called this unseen matter dunkle materie (dark matter). These observations were practically ignored for almost four decades until a large number of new evidences corroborating the claim of Oort and Zwicky emerged. Nowadays evidences advocating the existence of Dark Matter (DM) range from the galactic scale, where DM is needed to explain the observed stellar dynamics, to cosmological scales, DM being one of the pillars of the ΛCDM model. However, despite its central role, the nature of the DM remains unknown. This ignorance, which mostly stems from our inability to detect nongravitational interactions between dark and baryonic matter, together with the fact that DM is one of the few phenomenological flaws of the Standard Model (SM) has driven a huge activity in the theoretical community.1 However, if the lack of information about the DM properties makes quite easy is to come up with plausible theoretical solutions it also makes very hard to proof or disproof them. Thus it is crucial to keep pushing the experimental frontiers in parallel with the theoretical efforts. In the following we summarize the (few) experimental informations we have about the DM, and the experimental endeavors that the community is undergoing in the attempt to unveil some of its key features. [...]
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Danninger, Matthias. "Searches for Dark Matter with IceCube and DeepCore : New constraints on theories predicting dark matter particles." Doctoral thesis, Stockholms universitet, Fysikum, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-89820.
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The cubic-kilometer sized IceCube neutrino observatory, constructed in the glacial ice at the South Pole, searches indirectly for dark matter via neutrinos from dark matter self-annihilations. It has a high discovery potential through striking signatures. This thesis presents searches for dark matter annihilations in the center of the Sun using experimental data collected with IceCube. The main physics analysis described here was performed for dark matter in the form of weakly interacting massive particles (WIMPs) with the 79-string configuration of the IceCube neutrino telescope. For the first time, the DeepCore sub-array was included in the analysis, lowering the energy threshold and extending the search to the austral summer. Data from 317 days live-time are consistent with the expected background from atmospheric muons and neutrinos. Upper limits were set on the dark matter annihilation rate, with conversions to limits on the WIMP-proton scattering cross section, which initiates the WIMP capture process in the Sun.These are the most stringent spin-dependent WIMP-proton cross-sections limits to date above 35 GeV for most WIMP models. In addition, a formalism for quickly and directly comparing event-level IceCube data with arbitrary annihilation spectra in detailed model scans, considering not only total event counts but also event directions and energy estimators, is presented. Two analyses were made that show an application of this formalism to both model exclusion and parameter estimation in models of supersymmetry. An analysis was also conducted that extended for the first time indirect dark matter searches with neutrinos using IceCube data, to an alternative dark matter candidate, Kaluza-Klein particles, arising from theories with extra space-time dimensions. The methods developed for the solar dark matter search were applied to look for neutrino emission during a flare of the Crab Nebula in 2010.
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Sivertsson, Sofia. "Dark matter in and around stars." Licentiate thesis, Stockholm : Skolan för teknikvetenskap, Kungliga Tekniska högskolan, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-11259.
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Righi, Nicole. "Fuzzy dark matter from string axions." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2019. http://amslaurea.unibo.it/18010/.
Full textAbstract:
In this thesis we study the viability for ultra-light axions coming from moduli stabilisation in the Large volume scenario to fit recent observations about the dark matter presence in several galaxies and clusters. After a historical introduction on the dark matter problem and a review of the candidates proposed as dark matter constituents through the years, in Chapter 1 we present WIMPs and ALPs, which are nowadays believed to be the most likely constituents. In Chapter 2 we give the theoretical basis to analyse these particles, that is Supersymmetry and String theory, focusing especially on dimensional reduction and string compactifications in order to derive an effective theory. Then, in Chapter 3 we discuss the issue of moduli stabilisation and we deal with it in the Large volume scenario, examining the examples of Swiss cheese and Fibred Calabi-Yau manifolds. Finally, in Chapter 4 we present the original results of this thesis. Starting from recent observations claiming the existence of a preferred range of masses for the ultra-light axions constituting dark matter, we provide a theoretical explanation in the Large volume scenario. We demonstrate that a preferable mass exists for these axions and that axions having this mass could account for the total observed dark matter abundance in a natural way. In addition to this, we examine how to provide several axions with different masses by imposing reasonable cosmological hierarchies. Finally, we show how to generalise these results to Calabi-Yau manifolds with any number of axions, while in Chapter 5 some interesting outlooks of the present work are discussed.
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Massaro, Daniele. "Loop-induced annihilation of dark matter." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2019. http://amslaurea.unibo.it/19428/.
Full textAbstract:
Plenty of evidences suggest the existence of a new type of non-luminous matter in the Universe, that has been called dark matter. Its nature is still unresolved, however, there is a widespread belief that is a new particle. Today we have three important search strategies for dark matter: indirect detection, direct detection and collider searches. In this thesis we focus on indirect detection, which investigates the products of annihilation of dark matter in overdense regions of the Universe. In particular we focus on gamma-ray observations, considering the gamma-ray line signal, arising from dark matter annihilation into a pair of monochromatic photons. For electrically neutral dark matter, this process can proceed only via loop diagrams. Its computation can be done using numerical techniques. Numerical tools are a huge step forward in the dark matter research, and help scientists to make predictions and improve their models. However, at the current status there is no tool allowing for the calculation of loop-induced gamma-ray signals for arbitrary models. In this thesis we make an important step towards filling this gap. We focus on the numerical tool MadDM, and we validate the feature of automatised loop-induced computation using two dark matter models: the singlet scalar Higgs portal model and a simplified top-philic model. We then constrain the parameter space of these models using the current experimental results. In particular we consider the upper limits on gamma-ray line searches obtained by Fermi-LAT and HESS collaborations, finding that they provide important constraints on the parameters of both models.
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Zemp, Marcel. "The stability of dark matter cusps /." Zürich : ETH, Eidgenössische Technische Hochschule Zürich, Institute of Theoretical Physics, 2003. http://e-collection.ethbib.ethz.ch/show?type=dipl&nr=236.
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Fedotova, Veronika. "Constraining leptophilic dark matter with KM3NeT." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2021. http://amslaurea.unibo.it/23181/.
Full textAbstract:
Revealing the nature of the dark matter is among the most puzzling issues of today particle physics, astrophysics and cosmology.
Given the striking evidences for dark matter at all astrophysical scales, starting from galactic and going to cosmological scales, a widespread and well motivated assumption on the nature of the dark matter is that it is made by a new particle that extends the Standard Models of Particle Physics.
Indirect detection of dark matter, which annihilates in over-dense regions like the galactic centre, is an important probe of a possible dark matter interaction with the Standard Model particles. It could provide insights both to the underlying production mechanism of dark matter in the early Universe, on the annihilation properties at present time in galactic halos and on the underlying particle physics model.
In this master thesis project we will focus on simplified leptophilic models for dark matter. These models feature an massive boson, called for instance Z', and a Dirac dark matter candidate, that complement the Standard Model of particle physics.
We will study the annihilation of dark matter into leptons, focusing in particular on neutrino lines and box-shaped energy spectra. These tow signals are smoking gun signature to discover the dark matter properties. We will perform a numerical analysis using the dark matter software MadDM to predict the expected flux from the galactic centre, by performing scans in the model parameter space. We will implement the constrains from the Fermi-LAT telescope and the XENON1T experiment. Finally we will use the predictions of those models to assess the reach of the future KM3NeT neutrino telescope.
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Esch, Ernst-Ingo. "Detector development for dark matter research." [S.l. : s.n.], 2001. http://deposit.ddb.de/cgi-bin/dokserv?idn=962819433.
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Dal, Lars Andreas. "Antideuterons as Signature for Dark Matter." Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for fysikk, 2011. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-12634.
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In this thesis, we examine the antideuteron spectra from annihilations of dark matter in the form of Weakly Interacting Massive Particles (WIMPs). The so-called coalescence model is commonly used to describe the production of antideuterons. This model can be applied directly within a Monte Carlo simulation, but traditionally, approximations have been made that allow coalescence to be applied to the produced nucleon energy spectra after the simulation is done. The traditional approach is based on the assumption that the nucleons produced have isotropically distributed momenta, and is still commonly used today.We find that the assumption of isotropy does not hold; the final state particles from WIMP annihilations are confined in jets, something which increases the antideuteron yield. This effect is missed by the traditional approach, and using the direct implementation of the coalescence model leads to an order of magnitude enhancement of the antideuteron yield. Furthermore, we find that incorrect treatment of input gauge bosons as on-shell particles in Monte Carlo generators lead to underestimates of the antideuteron flux from WIMP annihilations into gauge bosons. This effect is particularly important when using the traditional application of the coalescence model.We also consider the contributions to the antideuteron spectrum from higher order annihilation processes, and find that for the lightest MSSM neutralino as WIMP candidate, these contributions are likely to become important for neutralino masses in the TeV range.
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Wilkinson, Ryan. "Deciphering dark matter with cosmological observations." Thesis, Durham University, 2016. http://etheses.dur.ac.uk/11762/.
Full textAbstract:
Determining the nature of dark matter (DM) remains one of the key challenges in both particle physics and cosmology. Although we know the approximate distribution of DM in the Universe, we lack an understanding of its fundamental properties such as its mass and potential couplings to Standard Model particles. In the weakly-interacting massive particle (WIMP) paradigm, DM was in thermal equilibrium in the early Universe and we should expect scattering to have occurred between DM and Standard Model particles. In this thesis, we first consider the impact of primordial scattering between DM and radiation (photons or neutrinos). Such interactions give rise to a modification in the amplitude and position of the cosmic microwave background (CMB) acoustic peaks and a series of damped oscillations in the matter power spectrum. We obtain constraints from the Planck satellite and other CMB experiments, and then derive limits from large-scale structure (LSS) surveys. By providing forecasts for future experiments, we illustrate the power of LSS surveys in probing deviations from the standard cold DM (CDM) model. Then, using high-resolution N-body simulations, we show that the suppressed matter power spectra in such interacting DM scenarios allows one to alleviate the small-scale challenges faced by CDM; in particular, the "missing satellite" and "too big to fail" problems. Finally, we show that the excess of 511 keV gamma-rays from the Galactic centre, which has been observed by numerous experiments for four decades, cannot be explained via annihilations of light WIMPs, suggesting an astrophysical or more exotic DM source of the signal.
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Trott, Cathryn Margaret. "Structure of dark matter in galaxies /." Connect to thesis, 2004. http://eprints.unimelb.edu.au/archive/00000906.
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Lindgren, Carrigan Marcus. "Neutrino Signals from Light Dark Matter." Thesis, KTH, Fysik, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-116706.
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Kerins, Eamonn John. "Baryonic dark matter and its detection." Thesis, Queen Mary, University of London, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.243974.
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Sming, Yue-Lin Sming. "Observational signatures of supersymmetric dark matter." Thesis, University of Sheffield, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.544174.
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Kalkitsas, Nikolaos, and Thom Jäderlund. "Simulation of Dark Matter Using micrOMEGAs." Thesis, KTH, Teoretisk fysik, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-167805.
Full textAbstract:
Weakly interactive massive particles (WIMPs) are one of the most popular dark matter candidates and in our study we have decided on a WIMP based model due to its accurate predictions of the dark matter (DM) relic density. To determine a possible WIMP, we have used the minimal supersymmetric model (MSSM), an extension of superymmetry (SUSY). Using micrOMEGAs we have made predictions of the direct and indirect detection for two different sets of parameters for a MSSM model considering the neutralino as the lightest supersymmetric particle (LSP). The results showed a discrete difference for the two sets of parameters in order of magnitude and the energy range, experimental data can rule in favour of one of the sets accordingly. We also found that it was preferable to have indirect detectors aimed at the Sun rather than the Earth.Weakly Interactive Massive Particles (WIMPs) anses vara en av de mest populära kandidaterna för mörk materia och i denna studie har en supersymmetrisk WIMP modellanvänts, där supersymmetrin beskrivs av den minimala supersymmetriska modellen (MSSM) och WIMPs för dess noggranna förutsägelse av relikdensiteten hos mörk materia. Simuleringar gjordes i programmet micrOMEGAs för direkt och indirekt detektion baserat på två varianter av MSSM-modellen och antagandet att neutralinon är den lättaste supersymmetriska partikeln (LSP). Resultaten visade en tydlig skillnad mellan de två varianterna i storleksordning och energiomfång och således kan experimentellt data uppmätts, vilket kan gynna en av varienterna. Det har även framgått att indirekt detektion är mer lämpat att studera med solen som källa, än jorden.
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Roldán, Carlos Antonio Calcáneo. "The evolution of dark matter substructure." Thesis, Durham University, 2001. http://etheses.dur.ac.uk/4232/.
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This thesis investigates the dynamical evolution of systems orbiting within deeper potentials. Initially we use a simple satellite-halo interaction to study the dynamical processes that act on orbiting systems and we compare these results to analytical theory. Deep images of the Centaurus cluster reveal a spectacular arc of diffuse light that stretches for over 100 kpc and yet is just a few kpc wide. We use numerical simulations to show that this feature can be produced by the tidal debris of a spiral galaxy that has been disrupted by the potential of one of the central cD galaxies of the cluster. The evolution of sub-halos is then studied in a cosmological context using high resolution N-body simulations of galactic mass halos that form in a cold dark matter (CDM) simulation. CDM halos form via a complex series of mergers, accretion events and violent relaxation. Halos are non-spherical, have steep singular density profiles and contain many thousands of surviving dark matter substructure clumps. This will lead to several unique signatures for experiments that aim to detect dark matter either indirectly, through particle annihilation, or directly in a laboratory. For the first time it is possible to construct maps of the gamma-ray sky that result from the annihilation of dark matter particles within simulated dark matter halo distributions.
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Jubb, Thomas William. "Dark matter : no place for WIMPs." Thesis, Durham University, 2017. http://etheses.dur.ac.uk/12369/.
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The primary goal of this thesis will be to explore the 'model space' of 'Weakly Interacting Massive Particle' (WIMP) 'Dark Matter' (DM), using simplified models in order to make some general statements on the allowed parameter space and to guide future detection efforts. The context for this thesis is a time in which many experiments are attempting, either directly or indirectly, to pin down the interactions of DM with the very precisely measured standard model. So far no robust signals have been found. Depending on your particular tastes, you may hold out for one particular realization of 'Beyond the Standard Model' (BSM) physics (e.g. Supersymmetry) and explore its rich phenomenology to ever increasing precision. But as time marches on, with diminishing confidence in discovery despite concerted efforts, you may instead look for ways in which to explore all possible realizations at once, a 'bottom-up' approach, to help guide future searches and model building efforts. This is the utility of simplified models. We will show that much of the parameter space of a neutral thermal WIMP (with arbitrary spin, spanning a complete set of simplified models) is heavily constrained by a combination of indirect/direct searches. Inevitably, carrying out such a study requires many assumptions, not all of them sound all of the time. To test the robustness of the study we will take an in-depth phenomenological look at a more detailed model, tackling many of the assumptions of simplified models (such as minimal flavour violation and gauge-invariance). We will take several detours along the way. We will show that the next generation of direct detections machines will be sensitive detectors for light (sub GeV) new particles in the neutrino sector. We will also consider how heavy flavour observables might be impacted by the breakdown of the assumption of quark-hadron duality, rather than from genuine new physics.
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Contenta, Filippo. "Probing dark matter with star clusters." Thesis, University of Surrey, 2017. http://epubs.surrey.ac.uk/844882/.
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Star clusters are collisional and dark matter (DM) free stellar systems, where their evolution is ruled by two-body interactions and the galactic potential. Using direct summation N-body simulations, I study how the observational properties of star clusters can be used to: (i) distinguish between DM free and DM dominated objects. From observations, the nature of several faint stellar systems in the Milky Way halo is not clear, therefore, I quantify the contribution of star clusters to the faint stellar systems population. (ii) Probe the underlying DM density of their host galaxy. I apply a new method to the recently discovered Eridanus~II ultra-faint dwarf galaxy that hosts a star cluster in its centre. I find that a cored DM density profile naturally reproduces the observed properties of Eridanus II’s star cluster. (iii) Infer their progenitor properties if they are accreted star clusters, such as Crater. From its properties I find that Crater is likely to be tidally stripped from a dwarf galaxy, and it must have formed extended and with a low concentration. Throughout this thesis, the comparison of simulations and data took into consideration observational biases and uncertainties. I show that the initial conditions of star clusters can heavily influence its present-day properties, and that the stellar evolution prescriptions can also impact the final star cluster properties, such as the neutron stars natal kick distribution. I conclude, through a series of test cases, that N-body simulations can be used to reproduce the observed properties of star clusters, and these can ultimately probe their host galaxy DM distribution.
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Kahlhoefer, Felix Karl David. "Complementarity of searches for dark matter." Thesis, University of Oxford, 2014. http://ora.ox.ac.uk/objects/uuid:ec5b1afe-b75c-44d9-9dad-e0d342e46fa1.
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The striking evidence for the existence of dark matter in the Universe implies that there is new physics to be discovered beyond the Standard Model. To identify the nature of this dark matter is a key task for modern astroparticle physics, and a large number of experiments pursuing a range of different search strategies have been developed to solve it. The topic of this thesis is the complementarity of these different experiments and the issue of how to combine the information from different searches independently of experimental and theoretical uncertainties. The first part focuses on the direct detection of dark matter scattering in nuclear recoil detectors, with a special emphasis on the impact of the assumed velocity distribution of Galactic dark matter particles. By converting experimental data to variables that make the astrophysical unknowns explicit, different experiments can be compared without implicit assumptions concerning the dark matter halo. We extend this framework to include annual modulation signals and apply it to recent experimental hints for dark matter, showing that the tension between these results and constraints from other experiments is independent of astrophysical uncertainties. We explore possible ways of ameliorating this tension by changing our assumptions on the properties of dark matter interactions. In this context, we propose a new approach for inferring the properties of the dark matter particle, which does not require any assumptions about the structure of the dark matter halo. A particularly interesting option is to study dark matter particles that couple differently to protons and neutrons (so-called isospin-violating dark matter). Such isospin-violation arises naturally in models where the vector mediator is the gauge boson of a new U(1) that mixes with the Standard Model gauge bosons. In the second part, we first discuss the case where both the Z' and the dark matter particle have a mass of a few GeV and then turn to the case where the Z' is significantly heavier. While the former case is most strongly constrained by precision measurements from LEP and B-factories, the latter scenario can be probed with great sensitivity at the LHC using monojet and monophoton searches, as well as searches for resonances in dijet, dilepton and diboson final states. Finally, we study models of dark matter where loop contributions are important for a comparison of LHC searches and direct detection experiments. This is the case for dark matter interactions with Yukawa-like couplings to quarks and for interactions that lead to spin-dependent or momentum suppressed scattering cross sections at tree level. We find that including the contribution from heavy-quark loops can significantly alter the conclusions obtained from a tree-level analysis.
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Lasenby, Robert. "New phenomenology from asymmetric dark matter." Thesis, University of Oxford, 2015. https://ora.ox.ac.uk/objects/uuid:ac7e21bc-c79b-49cc-9303-6b3fb5783e75.
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The properties of dark matter - its microphysical form, and its cosmological origin and history - are one of the most important mysteries in fundamental physics. So far, evidence for matter beyond the Standard Model comes entirely from gravitational effects. However, other experiments are reaching the point where the 'simplest' models of dark matter are coming into tension with data, and may be strongly constrained by medium-term observations. This, along with theoretical considerations, motivates the exploration of other possibilities for the history and composition of dark matter, especially those with the possibility of new, generic observational signatures. In this thesis, we explore some different classes of new dark matter models, focussing on regimes in which they may display approximately model-independent phenomenology. Firstly, we look at a class of dark matter models featuring large-number, stable composite states, and investigate how these may be synthesised in the early universe. As the example of Standard Model nuclear physics and Big Bang Nucleosynthesis demonstrates, the properties of small-number composite states in strongly-coupled theories may be complicated, and sensitive to the precise details of the theory. However, it may reasonably be expected that the properties of large enough composite states will obey simple geometrical scaling laws. In this case, if large enough states are synthesised in the early universe, the overall results of the synthesis process may become broadly independent of the detailed parameters of the model, and of initial conditions. We model 'dark nucleosynthesis' in such a regime, and find that the late-time number distribution takes on one of two characteristic forms, in both cases with weak dependence on small-number initial conditions and behaviour. Following on from this, we consider the scattering phenomenology that would result from dark matter being made up of such large composite states. This includes the coherent enhancement of scattering rates - for example, at direct detection experiments - compared to e.g. collider production processes. The spatially extended nature of composite dark matter states could also lead to characteristic momentum-dependent form factors in scattering processes, which may be identifiable in direct detection experiments. In addition, inelastic interactions between dark matter states may be important in astrophysical settings. Illustrating the effects of dark-sector energy injections, we present calculations for dark matter halo modifications through velocity kicks. As an example application, we discuss a different class of asymmetric dark matter models, in which late-time decays of part of the dark matter can re-populate a symmetric component, giving annihilation signals in galactic halos. The velocity kicks arising from the decay process may modify the spatial profile of such signals, to the extent to eliminating them almost completely from low-escape-velocity systems such as dwarf galaxies.
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Simha, Vimal. "Dark Matter Substructures and Galaxy Assembly." The Ohio State University, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=osu1313085907.
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Sidhu, Jagjit Singh. "Probing Macroscopic Dark Matter Parameter Space." Case Western Reserve University School of Graduate Studies / OhioLINK, 2021. http://rave.ohiolink.edu/etdc/view?acc_num=case1598956916361224.
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Han, Tao, Felix Kling, Shufang Su, and Yongcheng Wu. "Unblinding the dark matter blind spots." SPRINGER, 2017. http://hdl.handle.net/10150/623247.
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The dark matter (DM) blind spots in the Minimal Supersymmetric Standard Model (MSSM) refer to the parameter regions where the couplings of the DM particles to the Z-boson or the Higgs boson are almost zero, leading to vanishingly small signals for the DM direct detections. In this paper, we carry out comprehensive analyses for the DM searches under the blind-spot scenarios in MSSM. Guided by the requirement of acceptable DM relic abundance, we explore the complementary coverage for the theory parameters at the LHC, the projection for the future underground DM direct searches, and the indirect searches from the relic DM annihilation into photons and neutrinos. We find that (i) the spin-independent (SI) blind spots may be rescued by the spin-dependent (SD) direct detection in the future underground experiments, and possibly by the indirect DM detections from IceCube and SuperK neutrino experiments; (H) the detection of gamma rays from Fermi-LAT may not reach the desirable sensitivity for searching for the DM blind spot regions; (Hi) the SUSY searches at the LHC will substantially extend the discovery region for the blind-spot parameters. The dark matter blind spots thus may be unblinded with the collective efforts in future DM searches.
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Spolyar, Douglas. "Dark matter and the first stars /." Diss., Digital Dissertations Database. Restricted to UC campuses, 2009. http://uclibs.org/PID/11984.
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Reed, Darren S. "Cosmological simulations of dark matter halos /." Thesis, Connect to this title online; UW restricted, 2003. http://hdl.handle.net/1773/5443.
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