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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
261

Oscilação de neutrinos produzidos por aniquilação de matéria escura no sol / Neutrinos Oscillations Produced by Dark Matter annihilation in the Sun.

Britto, André Luiz Moura 17 October 2014 (has links)
Neste trabalho foi estudado como a materia escura pode ser capturada por corpos celestes e como a ela pode se comunicar com o Modelo Padrao atraves de sua aniquilacao em quarks e leptons. Os hadrons e leptons gerados podem decair em neutrinos que podem ser detectados por experimentos na Terra. Como tres tipos de neutrinos de autoestados de sabor ja foram observados experimentalmente e que diversos dados experimentais evidenciam oscilacao de sabor entre esses neutrinos, e preciso levar essa fenomenologia em consideracao ao estudar os neutrinos produzidos pela materia escura. O formalismo que permite considerar oscilacoes de neutrinos e ao mesmo tempo colisoes elasticas e inelasticas na materia e o formalismo de matriz densidade. Com ele estudamos o fluxo de muons gerados por neutrinos provenientes da aniquilacao da materia escura no interior do sol e como utilizar esse resultado para testes de modelos de particulas para materia escura. / In this work was studied how dark matter can be captured by celestial bodies and how it can communicate with the Standard Model through its annihilation in quarks and leptons. The hadrons and leptons generated can decay in to neutrinos which can be detected by experiments in Earth. As three types of neutrino flavor eigenstates have been observed experimentally and many experimental data have shown the flavor neutrino oscillate, it is necessary use this phenomenology when studying neutrinos produced by Dark Matter. The formalism that allows considering neutrino oscillations and, at same time, elastic and inelastic matter collisions is the density matrix formalism. With this formalism we studied the muons flux produced by neutrinos coming from dark matter annihilation inside the sun and how to use these results to test particle models for dark matter.
262

Research and Development of the Purification and Cryogenic Systems for the XENON1T Dark Matter Experiment

Contreras Palacios, Hugo Alejandro January 2015 (has links)
The evidence supporting the presence of Dark Matter in the universe ranges over many length scales: from the rotational curves within galaxies that cannot be explained only by the dust and other visible component to the anisotropies in the cosmological microwave background that sets the most precise quantification for the DM content in the universe at 26.8% of the energy density. One of the candidates for DM with the most theoretical support is a family of particles that appear in extensions of the Standard Model of Particles. These new particles, known as Weakly Interacting Massive Particles (WIMPs), provide a natural solution to the missing mass in the universe that interact only via weak interaction and whose origin dates back from the very early universe. The XENON Dark Matter search experiments aim to the direct detection of WIMPs via scattering off xenon nuclei. Following the success of the first prototype, XENON10, the XENON100 detector has been, up to late 2013, the most sensitive DM detector setting an upper bound limit on the spin-independent WIMP-nucleon cross-section of 2. × 10 −45 cm 2 and the spin-dependent equivalent of 3.5 × 10 −44 cm 2 . The detector consists of a dual-phase xenon Time Projection Chamber (TPC) with an inner target of 62 kg, located at the un- derground facility at Laboratori Nazionali del Gran Sasso (LNGS) in Italy. XENON100 is still in operation, currently testing new calibration sources of potential use for the next generation XENON1T experiment, under commissioning in Hall B of LNGS, aims to im- prove the XENON100 sensitivity by two orders of magnitude by increasing the xenon target mass in the detector to the tonne scale and by reducing the intrinsic background rate and consequently, increase the expected number of WIMP events per year. The scale-up of a liquid xenon TPC imposes many technical challenges that needed to be addressed prior to the realization of the XENON1T phase of the project. The focus of my thesis work has been the research and development of Dark Matter detectors operated with a xenon mass at the tonne scale. In particular, the topic of purification of a large amount of Xe gas to reduce the concentration of electronegative impurities to levels below afew parts per billion in a reasonable amount of time has been a driver in my work with the XENON1T Demonstrator facility at the Columbia Nevis laboratories. Two complementary approaches were followed in order to address this problem: i) a study of the performance of XENON100 concerning the electron lifetime (eLT) among other parameters that depend on the purity and ii) the construction of a full-size Xe TPC prototype to test multiple technologies with the goal of an optimized XENON1T TPC, with several tonnes of Xe. In addition to my work on the XENON1T Demonstrator, I have also contributed to the operation and analysis of data from XENON100. In particular, I developed a cut based on the information theory concept of entropy to reduce the electronic noise in the data. A detailed description of the motivation and implementation of the entropy cut is presented in Chapter 3. The experience gained from the successful performance of XENON100 and the information from variety of measurements with the XENON1T Demonstrator have influenced the design of XENON1T and will impact other next-generation Dark Matter detectors using LXe in a TPC. More specifically, the design of the XENON1T cryogenic system which is at the heart of the experiment, has been guided by this experience. The testing of the system was performed at Nevis where the various components were assembled and leak checked before being shipped to LNGS. The XENON1T detector’s cryostat and its cryogenics system, designed by the Columbia University XENON group were installed underground in the Hall B of the LNGS laboratory in Summer/Fall 2014. Their commissioning represent a major milestone in the realization of XENON1T. The last chapter of the thesis summarizes the status of XENON1T, with particular focus on the design of the cryogenic, purification and cryostat system influenced by the R & D with the Demonstrator.
263

Quadratic scalar-tensor gravity

Davies, Trevor Bamidelé January 2017 (has links)
This thesis develops novel analytic models of scalar-tensor theories with quadratic coupling. In this framework, the coupling strength between scalar and matter is regulated in a way that allows the vacuum expectation value to vanish for low matter densities while becoming non-vanishingly large in the high-density regime. This results in significant deviations from the predictions of General Relativity in the strong-gravity regime. In astrophysics, we addressed the core-collapse supernova problem to account for the apparently missing energy required to explain the observed powerful explosions. We assumed a small, massless scalar gravitational field, thus allowing General Relativity to be recovered in the weak-gravity asymptotic limit. The non-trivial effects coming from the coupling function in the presence of a high-density field were analyzed at the instant of neutron star formation. Our results show that the scalar gravitational field evolves from a cosmological value to a new equilibrium via a Higgs-like mechanism. Additionally, the calculations associated with the gravitational binding energy shift and relevant relaxation timescale are explicitly shown. The full theory space of the model was also investigated for positive values of the coupling parameter. We studied a mechanism to address the stalled shock issue in core-collapse scenarios, which involved the application of sufficiently large positive values to the coupling parameter. Our results show that pulsating neutron stars act like optical cavities in which resonant scalar waves are parametrically amplified. It implies that the surface of a neutron star acts like an anti-phase reflector, releasing traveling scalar gravitational waves similar to an optical laser. In cosmology, the same framework was applied to a generic Friedman-Robertson-Walker universe involving general metric coupling and scalar potential functions. In cosmology, the same framework was applied to a generic Friedman-Robertson-Walker universe involving general metric coupling and scalar potential functions. We developed a mechanism which allowed the scalar field to be dynamically trapped, thus generating a potential capable of driving primordial inflation. Our results show that a trapped scalar field produces non-trivial dynamical consequences when applied to standard cosmology. Additionally, our analytic solutions for the generic inflationary behaviour, produce acceptable duration and e-foldings, thus recovering the Hubble parameter which is consistent with the present-day value. A feature of our cosmological model is that the universe can undergo several accelerating or decelerating phases, even though the scalar potential and metric coupling are monotonic functions overall. As this is important for the current dark energy problem, the quasi-static motion of the gravitational field induced by the scalar potential in the early universe, is investigated for a small value of the scalar field with normalized metric at the present time. Our results show that a variable Lambda Cold Dark Matter universe emerges naturally from the quadratic model.
264

New Physics at Colliders and in Space / Nouvelle physique aux collisionneurs et dans l'espace

Robbins, Glenn 24 September 2018 (has links)
La quête de la nouvelle physique est un défi impliquant à la fois la recherche de particules de matière noire dans les halos galactiques, et celle, aux collisonneurs, de particules dont l’existence est prédite par des théories au-delà du Modèle Standard, telles que la supersymétrie. Alors que les contraintes expérimentales sur ces particules s’intensifient, il devient capital de combiner les limites provenant de ces deux volets afin de guider la suite des recherches. Pour ce faire, il est indispensable d’évaluer et de tenir compte correctement des incertitudes astrophysiques, cosmologiques et nucléaires, pourtant souvent ignorées. La première partie de cette thèse est dédiée à l’étude de ces incertitudes et leur impact sur les contraintes obtenues en supersymétrie, ainsi que la complémentarité entre les contraintes des collisionneurs et de matière noire pour la recherche de nouvelle physique. La deuxième partie est consacrée au développement d’outils de calculs pour les détections directe et indirecte de matière noire, conçus afin de prendre correctement en compte les incertitudes astrophysiques et nucléaires, et à leur implémentation dans le code public SuperIso Relic. Enfin la troisième partie du travail concerne l’étude des implications cosmologiques d’une éventuelle découverte de nouvelles particules aux collisionneurs. Nous avons montré qu’il serait possible de tester les hypothèses du modèle cosmologique standard et d’obtenir des informations sur les propriétés de l’Univers primordial à une époque observationnellement inaccessible / The quest for new physics is a challenging task which involves, on the one hand, the search for dark matter particles from space, and on the other hand, the search at colliders for particles predicted by theories beyond the Standard Model, such as supersymmetry. With the experimental constraints on new particles getting stronger, it becomes crucial to combine the limits from both sectors in order to guide future searches. To this end, it is essential to estimate and take into account correctly the astrophysical, nuclear and cosmological uncertainties, which are most often ignored. The first part of this thesis is dedicated to the study of such uncertainties and to their impact on the constraints applied on supersymmetry. Moreover, we investigate the interplay between the constraints from colliders and dark matter searches in some detail. The second part concerns the development and the implementation in the public code SuperIso Relic of numerical tools for the calculation of direct and indirect dark matter detection constraints which were designed specifically to take correctly into account astrophysical and nuclear uncertainties. Finally, in the third part of this work, we consider the cosmological implications of a hypothetical discovery of new particles at colliders. We show that it would be possible to test the assumptions of the standard cosmological model and to obtain information on the properties of the primordial Universe at an epoch which is beyond observational reach
265

Estudo da possibilidade de detecção da matéria escura com telescópios Cherenkov / Study of the possibility of dark matter detection with Cherenkov telescopes

Jéssica Arab Marcomini 18 June 2015 (has links)
A existência de matéria escura é sustentada pela observação de efeitos gravitacionais sobre a matéria comum. A partir desses efeitos, com medidas de curvas de rotação e lentes gravitacionais, é possível calcular a densidade de matéria escura necessária para causa-los. Para descrever o comportamento observado, foram criados alguns modelos teóricos, porém a natureza das partículas que constituem matéria escura continua desconhecida. Determinar propriedades como massa e seção de choque da possível partícula de matéria escura é fundamental para o entendimento da natureza de seus efeitos sobre matéria bariônica. No âmbito experimental, os Telescópios Cherenkov medem a radiação gama proveniente do cosmo com energia entre GeV &#8212TeV de forma que uma possível interação (como exemplo a aniquilação de partículas de matéria escura) poderia ter seu resultado final de raios gama detectado em um dos experimentos de observação indireta. Neste trabalho de mestrado analisamos os conceitos de matéria escura a partir de um modelo específico de partículas WIMPs, o neutralino. Estudamos galáxias anãs esferoidais como possíveis fontes do sinal de raios gama proveniente da aniquilação de neutralinos. Para o entendimento dos cálculos, reproduzimos os resultados de dois experimentos importantes para a área, pertencentes aos telescópios VERITAS e MAGIC, validando as implementações realizadas. Estudamos também galáxias anãs esferoidais observadas pelo experimento FERMI-LAT para as quais limites superiores de fluxo foram determinados. Fizemos uso dessas medidas e extrapolamos os espectros de energias para o intervalo a ser observado pelo CTA. Utilizando curvas de sensitividade realistas para uma possível configuração do CTA, determinamos a potencialidade de detectação de matéria escura pelo CTA de 18 fontes estudados pelo FERMI-LAT. A partir dos resultados obtidos com a simulação do Observatório, podemos concluir quais fontes proporcionam melhores avanços para as pesquisas envolvendo matéria escura com o modelo escolhido. / The existence of dark matter is sustained by the observation of its gravitational efects on ordinary matter. By studying these efects, with rotation curves and gravitational lensing measurements, it is possible to calculate the dark matter density necessary to cause them. Theoretical models were created to describe the observed behavior, however the nature of the constituent particles is still unknown. Determining the particles\' properties such as mass and cross section is fundamental for the understanding of the nature of its efects on baryonic matter. On the experimental scope, Cherenkov Telescopes measure the gamma radiation coming from the cosmo with an energy between GeV &#8212TeV making it possible for an interaction to have its final product detected in one of these experiments. In this dissertation, we present an analysis of dark matter concepts considering a specific model of WIMPs particles, represented by the neutralino. We studied dwarf spheroidal galaxies as possible gamma-ray flux sources originated from the neutralino annihilation. We reproduced the results on annihilation cross section of two important experiments for this particular field (VERITAS and MAGIC), validating the codes implemented. This was perfomed with the objective of understanding the calculus involved. We studied dwarf spheroidal galaxies observed by the FERMI-LAT experiment for which upper limits flux were determined. We used these measurements and extrapolated the energy spectrum to the one to be observed by CTA. With realistic sensitivity curves for a possible CTA configuration, we determined the potencial for a dark matter detection for 18 sources studied by FERMI-LAT. With the results obtained with the Observatory simulation, we were able to conclude which of these sources represent improvements for dark matter researches with the specific model described.
266

Reduzindo o setor escuro do Universo: uma nova cosmologia acelerada com criação de matéria escura fria / Reducing the Dark Sector of the Universe: A New Accelerating Cosmology with Cold Dark Matter Creation

Oliveira, Felipe Andrade 03 May 2010 (has links)
Nesta dissertação nós propomos uma nova cosmologia relativística acelerada cujo conteúdo material é composto apenas por bárions e matéria escura fria. A não existência de uma componente de energia escura implica que nosso cenário é baseado numa redução do chamado setor escuro do universo. Neste modelo, o presente estágio acelerado é determinado pela pressão negativa descrevendo a produção de partículas de matéria escura fria induzida pelo campo gravitacional variável do universo. Para um universo espacialmente plano ($\\Omega _ + \\Omega _b = 1$), como previsto pela inflação, este tipo de cenário possui somente um parâmetro livre e a equação diferencial governando a evolução do fator de escala é exatamente a mesma do modelo $\\Lambda$CDM. Neste caso, encontramos que o parâmetro efetivo de densidade de matéria é $\\Omega_= 1 - \\alpha$, onde $\\alpha$ é um par\\^metro constante ligado à taxa de criação de matéria escura fria. Aplicando um teste estatístico $\\chi^2$ para os dados de Supernovas do tipo Ia (Union Sample 2008), limitamos os par\\^metros livres do modelo nos casos espacialmente plano e com curvatura. Em particular, encontramos que para o caso plano $\\alpha \\sim 0.71$, de forma que $\\Omega_ \\sim 0.29$, como tem sido inferido independentemente por lentes gravitacionais fracas, estrutura de grande escala, radiação cósmica de fundo e outras observações complementares. / In this dissertation we propose a new accelerating relativistic cosmology whose matter content is composed only by baryons and cold dark matter. The nonexistence of a dark energy component implies that our scenario is based on a reduction of the so-called dark sector of the Universe. The present accelerating stage in this model is powered by the negative pressure des\\-cribing the cold dark matter particle production induced by the variable gravitational field of the Universe. For a spatially flat universe ($\\Omega _ + \\Omega _b = 1$), as predicted by inflation, this kind of scenario has only one free parameter and the differential equation governing the evolution of the scale factor is exactly the same of the $\\Lambda$CDM model. In this case, we find that the effectively observed matter density parameter is $\\Omega_ = 1 - \\alpha$, where $\\alpha$ is a constant parameter related to the cold dark matter creation rate. By applying a $\\chi^2$ statistical test for Supernovae type Ia data (Union Sample 2008), we constrain the free parameters of the model for spatially flat and curved cases. In particular, to the flat case we find $\\alpha \\sim 0.71$, so that $\\Omega_ \\sim 0.29$, as independently inferred from weak gravitational lensing, large scale structure, cosmic background radiation, and other complementary observations.
267

Vinculando modelos de energia escura com idade de galáxias em altos redshifts / Constraint Dark Energy Models with High-Redshifts Galaxy Ages

Bachega, Riis Rhavia Assis 20 August 2014 (has links)
Uma série de observações advindas da medida da distância de supernovas tipo IA, idade das estrelas mais antigas, anisotropias da radiação cósmica de fundo, entre outras, evidenciam que o universo está passando por uma fase de expansão acelerada. Essa expansão está sendo causada por uma componente misteriosa denominada energia escura, que representa cerca de $70\\%$ do conteúdo total do universo, e cuja natureza é desconhecida. Para descrever a energia escura vários modelos têm sido propostos, entre eles, podemos destacar a energia do vácuo (constante cosmológica) e um campo escalar dinâmico (quintessência). Também são considerados modelos em que a energia escura interage com outro componente misterioso, a matéria escura. Existem vários testes observacionais para vincular os parâmetros desses modelos. Nesta dissertação, exploraremos um método baseado na idade de galáxias em altos redshifts e na idade do universo, conhecido em inglês como lookback time. / A number of observations arising from the measurement of distance of type IA Supernovae, age of oldest stars, anisotropy of cosmic microwave background, among others, show that the universe is undergoing a phase of accelerated expansion. This expansion is being caused by a mysterious component called dark energy, which represents about $70\\%$ of the total content of the universe, and whose nature is unknown. To describe the various dark energy models have been proposed, among them we highlight the vacuum energy (cosmological constant), and a dynamic scalar field (quintessence). Are also considered models in which dark energy interacts with another mysterious component, the dark matter. There are several observational tests to constraint the parameters of these models. In this dissertation, we explore a method based on age of galaxies at high redshift and the age of the universe, known as lookback time.
268

Recherches de WIMPs de basse masse et d'axions avec l'expérience EDELWEISS / Low mass WIMP and axion searches with the EDELWEISS experiement

Main de Boissière, Thibault 03 July 2015 (has links)
En dépit des récents succès de la cosmologie observationnelle, la majeure partie de l'univers demeure méconnue: la matière usuelle, dite baryonique, ne représente que 5% du contenu total de l'univers. Dans le modèle cosmologique standard, deux autres composantes complètent notre description: l'énergie noire et la matière noire (respectivement 70% et 25% du contenu total). Dans cette thèse, nous nous intéressons à la matière noire, une nouvelle forme de matière qui doit être non-relativiste, non-baryonique et neutre de charge. Nous avons étudié deux candidats : les WIMPs et les axions. Toutes nos analyses ont été menées au sein de la collaboration EDELWEISS, qui opère des détecteurs sensibles à un éventuel signal de WIMP ou d'axion. Les axions ont d'abord été introduits pour résoudre le problème de la symétrie CP en chromodynamique quantique. Ils peuvent être produits dans le soleil par des processus divers et, dans certains modèles, peuvent contribuer à la densité de matière noire. Nous avons utilisé les données d'EDELWEISS pour la recherche d'axions suivant quatre modes de production-détection distincts. Ces mécanismes font intervenir le couplage des axions aux nucléons, aux photons et aux électrons. Nous n'avons observé aucun excès de signal par rapport au bruit de fond. Ces constatations nous ont permis d'obtenir des contraintes fortes sur la valeur de chaque couplage d'axion et d'exclure plusieurs ordres de grandeur de la masse de l'axion dans le cadre de modèles spécifiques de QCD. Les WIMPs font partie des candidats à la matière noire les plus étudiés. Ce sont des particules interagissant faiblement avec une masse pouvant aller du GeV au TeV. Des modèles théoriques et des résultats expérimentaux récents semblent converger vers des masses faibles (de l'ordre de quelques GeV). à la lumière de ces développements, nous avons donc choisi de privilégier l'étude des WIMPs de basse masse (de 3 à 25 GeV). Nous avons mis en place une analyse multivariée particulièrement adaptée à la recherche de WIMPs de basse masse. Cette analyse a été optimisée sur une fraction de 35 kg.jour du jeu de données EDELWEISS complet. Nous n'avons pas observé d'excès de signal par rapport au bruit de fond attendu. Par conséquent, nous avons calculé une limite supérieure sur la section efficace WIMP-nucléon spin-indépendante de 1.48 × 10⁻⁶ pb à 10 GeV. / In spite of the recent successes of observational cosmology, most of the universe remains poorly known. Known particles (which we call baryons) only make up 5% of the total content of the universe. The standard cosmological model contains two other components: Dark Energy and Dark Matter (respectively 70% and 25% of the total content). Dark Matter, which is generally believed to be a non-relativistic, charge neutral and non-baryonic new form of matter, is the central focus of this work. We studied two likely candidates, namely WIMPs and axions. Our analyses were carried out within the EDELWEISS collaboration which operates detectors sensitive to both WIMP and axion signals. Axions were first introduced to solve the strong CP problem. They can be produced in the Sun through a variety of processes and in some models, they may also contribute to the Dark Matter density. In this work, we used EDELWEISS data to search for axions through four distinct production-detection mechanisms. These mechanisms involve the coupling of axions to nucleons, photons and electrons. No excess over background was found. These null observations allowed us to set stringent constraints on the axion couplings and exclude several orders of magnitude of the axion mass within specific QCD axion models. On the other hand, WIMPs are the canonical dark matter candidate whose mass lies in the GeV-TeV range. With the motivation of recent theoretical developments and possible signal hints, we focused our effort on so-called low mass WIMPs (3 to 25 GeV). This thesis describes a new multivariate analysis specifically designed for this mass range, which we tuned using an unblinded fraction of the data set (35 kg.d) from a single EDELWEISS detector. No significant signal over background excess was found and we set an upper limit on the spin-independent WIMP-nucleon cross section of 1.48 × 10⁻⁶ pb at 10 GeV.
269

Testes de modelos de matéria escura relacionados aos excessos leptônicos medidos pelo PAMELA e FermiLAT / Probes of dark matter-modelswhich explain the leptonic excesses measured by PAMELA and FermiLAT

Sotelo, Denis Stefan Robertson 18 September 2012 (has links)
Atualmente existem muitas evidências da presença de matéria escura no Universo. Estas motivaram a existência de vários experimentos para sua detecção. Entre os experimentos de detecção indireta de matéria escura, o PAMELA, o ATIC e o Fermi-LAT observaram recentemente excessos de elétrons e pósitrons no fluxo galáctico em relação ao esperado para estas partículas. Estes resultados podem ser explicados pela aniquilação de matéria escura com massas entorno a 1 TeV em nossa galáxia, com produção de léptons. No entanto, para tal, estas observações requerem um aumento na taxa de aniquilação relativa à esperada da produção térmica de matéria escura. Este aumento pode ser devido a existência de subestruturas de matéria escura no halo galáctico ou a mecanismos de interação, como o efeito Sommerfeld, que aumentam a seção de choque de aniquilação das partículas de matéria escura. Neste _ultimo caso, deve ocorrer também um aumento na taxa de neutrinos provenientes da aniquilação de matéria escura no núcleo da Terra. Neste trabalho, estimamos as taxas destes neutrinos e usamos os resultados finais do AMANDA-II e resultados recentes de IceCube para testar cenários genéricos que contemplam um aumento na seção de choque de aniquilação. Apresentamos os nossos resultados em função da seção de choque de interação da matéria escura com os núcleos multiplicada pela fração da aniquilação das partículas de matéria escura em neutrinos e, também em função de um fator genérico de boost que parametriza o aumento na seção de choque de aniquilação. Encontramos que modelos de matéria escura requerem fatores de boost da ordem O(100) ou mais e que se aniquilam significativamente em neutrinos são excluídos como explicação dos excessos leptônicos medidos. / Currently there are many evidences of the existence of dark matter in the Universe. These led to experimental dark matter searches and, among them, some indirect detection experiments, PAMELA, ATIC and Fermi-LAT, have recently observed excesses in the galactic flux of electrons and positrons relative to the expected flux of these particles. These results could be explained by dark matter, with masses of the order of 1 TeV, annihilating into leptons in our galaxy. However, in order for this to explain the mentioned excesses, it is required that the dark matter annihilation rate is greater than the implied rate assuming the expected dark matter thermal annihilation cross section. This greater rate could be due to the presence of dark matter substructures in the galactic halo or due to interaction mechanisms, such as the Sommerfeld effect, that enhance the dark matter annihilation cross section. In the latter case, an enhancement in the neutrino flux from annihilation of dark matter particles in the Earth nucleus should also occur. In this work, we use the final results of AMANDA-II and recent results of IceCube to probe generic enhancement scenarios. We present results as a function of the dark matternucleon interaction cross section weighted by the branching fraction into neutrinos, and as a function of a generic boost factor, which parametrizes the expected enhancement of the annihilation rate. We find that dark matter models that require boosts factors of O(100) or more and that annihilate mainly into neutrinos are excluded as a explanation for the observed leptonic excesses.
270

The Role of Angular Momentum in the Interplay Between Disk Galaxies and Their Host Dark Matter Halos: Corollaries for the Hubble Fork Diagram

Collier, Angela 01 January 2019 (has links)
A majority of disk galaxies host stellar bars that regulate and amplify the flow of angular momentum, J, between disks and their parent dark matter (DM) halos. These bars constitute the prime factor driving internal galaxy evolution. Yet, a non-negligible fraction of disks lack this morphological feature, which led to adoption of the Hubble Fork Diagram. The complex evolution of barred galaxies has been studied by means of numerical simulations, complemented by observations. Despite prolonged efforts, many fundamental questions remain, in part because cosmological simulations still lack the necessary resolution to account for resonant interactions and simulations of isolated galaxies have ignored the cosmological spin of halos. The goal of my thesis is to analyze the J-redistribution in barred galaxies embedded in spinning DM halos, and quantify the DM response. Using high-resolution N-body stellar and DM numerical simulations, I model and analyze the dynamical and secular evolution of stellar bars in disk galaxies and their DM counterparts —induced DM bars in spinning halos with a range of cosmological spin parameter λ ~ 0-0.09. Using a novel method to create initial conditions for the self-consistent equilibrium disk-halo systems, and evolving them for 10 Gyr, I follow the basic parameters of stellar and DM bars, including their observational corollaries. My conclusions are based on nonlinear orbit analysis which quantifies the orbit trapping by the resonances. My main results emphasize a new effect: the DM halo spin has a profound effect on the evolution of stellar and DM bars. Specifically, with increasing λ in the prograde direction: (1) stellar bars develop faster dynamically, but (2) experience a reduced growth during the secular phase of evolution, and basically dissolve for λ > 0.06. These disks can represent the unbarred branch of galaxies on the Hubble Fork Diagram; (3) the stellar bar pattern speeds level off and lose less J; and (4) the stellar bars exhibit ratios of corotation-to-bar radii, RCR/Rbar > 2, representing the so-called slow bars without offset dust lanes. Furthermore, I find that (5) the induced DM bars reach maximal amplitudes which strongly depend on λ, while those of the stellar bars do not; (6) efficiency of resonance trapping of DM orbits by the DM bars, their masses and volumes — all increase with λ; (7) contribution of resonant transfer of J to the DM halo increases with λ as well. (8) prograde and retrograde DM orbits play different roles in J-transfer. (9) Finally, I find that dependence of DM response on λ has important implications for a direct detection of DM and of the associated stellar tracers, such as 'streamers.' Additional results relate the above analysis of corotating disks and halos with those of the counter-rotating ones.

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