La présence de grandes quantités de matière noire invisible, c'est-à-dire non lumineuse, donc sans couplage avec les photons, autour des galaxies et à l'intérieur de leurs amas, a été confirmée par toute une série d'observations indépendantes au niveau galactique, extragalactique et cosmologique. De quoi cette matière noire est composée représente un des mystères de l'Univers qui intrigue cosmologistes et physiciens des particules. Les modèles supersymétriques proposent des candidats naturels : les WIMPs (Weakly Interacting Massive Particle). Dans la plupart des cas de figure, l'Univers est suffisamment rempli de WIMPs pour qu'il soit possible de les détecter indirectement ou directement. Pendant mon doctorat, je me suis intéressée à la recherche directe de matière noire au sein de la collaboration EDELWEISS. EDELWEISS est une expérience de recherche directe de matière noire, cette dernière interagissant avec la matière baryonique par diffusion élastique. Dans le but de mesurer les énergies des reculs nucléaires dus à ces rares interactions, EDELWEISS emploie des détecteurs cryogéniques à double composante chaleur et ionisation (de type Ge-NTD). Chacun de ces détecteurs est constitué d'un cristal de Germanium de 320g, refroidi à une température de 20 mK. La mesure simultanée de deux signaux chaleur et ionisation permet la discrimination entre les reculs électroniques et les reculs nucléaires, ces derniers étant principalement induits par des WIMPs ou des neutrons. Le coeur de mon travail de thèse a été l'analyse des données du run 8 de physique comportant 11 bolomètres caractérisés par une très bonne stabilité en termes de résolution ligne de base et correspondant à une exposition fiducielle de 93.5 kg.j. Les différentes étapes de l'analyse sont détaillées ci-dessous. J'ai commencé par l'étalonnage des détecteurs cryogéniques avec des sources gamma 133Ba et neutron Am-Be dans le but d'évaluer leurs performances dans l'environnement du nouveau cryostat EDELWEISS-II et de la nouvelle chaîne d'acquisition. Ensuite j'ai traité l'optimisation des méthodes d'analyse et des paramètres de la chaîne de lecture des données. Enfin les résultats sont interprétés en termes de limite sur la section efficace d'interaction d'un WIMP avec un nucléon en fonction de la valeur de sa masse. Pour un seuil en énergie de recul de 30 keV (choisi a priori), 3 événements ont été enregistrés dans la bande de reculs nucléaires, correspondant à une sensibilité de 5*10^-7 pb pour une masse de WIMP de 80 GeV/c^2. J'ai également mené une étude pour comprendre le bruit de fond radioactif résiduel, regardant avec attention le fond gamma et le fond beta provenant du 210Pb. Pour ce dernier, un bolomètre Ge-NTD a été équipé avec une source de 210Pb. Le fond gamma pour des énergies supérieures à 100 keV montre une réduction globale et uniforme d'un facteur deux par rapport à la première phase de l'expérience, EDELWEISS-I, arrêtée en 2004. [....] Cette étude a permis de prédire le nombre de betas de basse énergie attendus pour le run de physique. Cette prédiction se révèle compatible avec le spectre expérimental de trois événements observés dans la zone des reculs nucléaires. Néanmoins cela n'est pas suffisant pour permettre une soustraction du fond, du fait des grandes incertitudes liées au profil de collection de charge et au profil d'implantation du Pb / One of the greatest mysteries of the universe that, for the present, puzzles the mind of most astronomers, cosmologists and physicists is the question: "What makes up our universe?". This is due to how a certain substance named Dark Matter came under speculation. It is believed this enigmatic substance, of type unknown, accounts for almost three-quarters of the cosmos within the universe, could be the answer to several questions raised by the models of the expanding universe astronomers have created, and even decide the fate of the expansion of the universe. There is strong observational evidence for the dominance of non-baryonic Dark Matter (DM) over baryonic matter in the universe. Such evidence comes from many independent observations over different length scales. The most stringent constraint on the abundance of DM comes from the analysis of the Cosmic Microwave Background (CMB) anisotropies. In particular, the WMAP (Wilkinson Microwave Anisotropy Probe) experiment restricts the abundance of matter and the abundance of baryonic matter in good agreement with predictions from Big Bang Nucleosynthesis. It is commonly believed that such a non-baryonic component could consist of new, as yet undiscovered, particles, usually referred to as WIMPs (Weakly Interacting Massive Particles). Some extensions of the standard model (SM) of particle physics predict the existence of particles that would be excellent DM candidates. In particular great attention has been dedicated to candidates arising in supersymmetric theories: the Lightest Supersymmetric Particle (LSP). In the most supersymmetric scenarios, the so-called neutralino seems to be a natural candidate, being stable in theories with conservation of R-parity and having masses and cross sections of typical WIMPs. The EDELWEISS collaboration is a direct dark matter search experiment, aiming to detect directly a WIMP interaction in a target material, high purity germanium crystal working at cryogenic temperatures. It relies in the measurement of nuclear recoils that produce measurable effects in the crystal such ionization and heat. My PhD thesis is organized as follows. The first chapter aims to provide an introduction to the theoretical framework and the scientific motivation for the following work. The nature of DM has been one of the most challenging topics in contemporary physics since the first evidences of its existence had been found in the 1930s. Cosmologists and astrophysicists on one side, together with particle theorists on the other have put a lot of effort into this field: I will briefly account for their achievements and for the experimental strategies which can be set in this scenario. Since this thesis work was carried out within the EDELWEISS-II direct dark matter experiment, I will focus the next chapter on this topic, describing the main features. The second chapter is related to the set-up of the EDELWEISS-II, the current stage of the EDELWEISS experiment necessary after a first phase that achieved the best upper limit on the WIMP elastic scattering on nucleon as a function of WIMP mass in 2004. [....]

Les observations de la structure à grande échelle de l'Univers sont précieuses pour établir et tester des théories cosmologiques sur son origine et son évolution. Cette démarche requiert des outils appropriés d'assimilation des données, afin d'établir le contact entre les catalogues de galaxies et les modèles de formation des structures.Dans cette thèse, une nouvelle approche pour l'analyse ab initio et simultanée de la formation et de la morphologie de la toile cosmique est présentée : l'algorithme BORG infère les fluctuations de densité primordiales et produit des reconstructions physiques de la distribution de matière noire, en assimilant les relevés de galaxies dans un modèle cosmologique de formation des structures. La méthode, basée sur la théorie bayésienne des probabilités, fournit un moyen de quantifier précisément les incertitudes.On présente l'application de BORG aux données du Sloan Digital Sky Survey et on décrit la structure de l'Univers dans le volume considéré. On démontre que cette approche a mené à la première inférence quantitative des conditions initiales et du scénario de formation des structures observées. On utilise ces résultats pour plusieurs projets cosmographiques visant à analyser et classifier la toile cosmique. En particulier, on construit un catalogue de vides, décrits au niveau de la matière noire et non des galaxies. On présente des cartes probabilistes détaillées de la dynamique de la toile cosmique et on propose une solution générale pour la classification des structures en présence d'incertitude.Les résultats de cette thèse constituent une précise description chrono-cosmographique des inhomogénéités de la structure cosmique. / Surveys of the cosmic large-scale structure carry opportunities for building and testing cosmological theories about the origin and evolution of the Universe. This endeavor requires appropriate data assimilation tools, for establishing the contact between survey catalogs and models of structure formation.In this thesis, we present an innovative statistical approach for the ab initio simultaneous analysis of the formation history and morphology of the cosmic web: the BORG algorithm infers the primordial density fluctuations and produces physical reconstructions of the dark matter distribution that underlies observed galaxies, by assimilating the survey data into a cosmological structure formation model. The method, based on Bayesian probability theory, provides accurate means of uncertainty quantification.We demonstrate the application of BORG to the Sloan Digital Sky Survey data and describe the primordial and late-time large-scale structure in the observed volume. We show how the approach has led to the first quantitative inference of the cosmological initial conditions and of the formation history of the observed structures. We then use these results for several cosmographic projects aiming at analyzing and classifying the large-scale structure. In particular, we build an enhanced catalog of cosmic voids probed at the level of the dark matter distribution, deeper than with the galaxies. We present detailed probabilistic maps of the dynamic cosmic web, and offer a general solution to the problem of classifying structures in the presence of uncertainty.The results described in this thesis constitute accurate chrono-cosmography of the inhomogeneous cosmic structure.

Élucider le mystère de la matière noire est l’un des plus grands défis de la physique moderne, à l’interface entre l’astrophysique, la cosmologie et la physique des particules. Dans cette thèse, j’aborde différents aspects de la recherche indirecte des particules de matière noire, approche complémentaire à la détection directe et à la production dans des collisionneurs. Nous entrons dans une nouvelle ère grâce à des instruments remarquables et c’était donc le moment opportun pour s’attaquer au problème du profil de densité de matière noire au centre des galaxies par des méthodes originales. C'est la motivation principale de ma thèse. Dans ce travail, je tire parti des avancées technologiques afin d’explorer de nouvelles façons d’étudier la région centrale des halos de matière noire. Je me concentre en particulier sur les pics de matière noire, qui correspondent à des augmentations extrêmement fortes de la densité de matière noire pouvant être induites par les trous noirs supermassifs. Je montre qu’il est possible d’aller au-delà des recherches standards en étudiant les photons émis par des électrons et positrons produits dans les processus d’annihilation des particules de matière noire. Dans ce contexte, je décris une nouvelle technique pour modéliser la propagation des rayons cosmiques pour des profils d'injection très piqués. Je développe des modèles originaux de l’émission diffuse dans les régions centrales des galaxies, pour la Voie Lactée mais également pour d’autres galaxies, ce qui permet d’expliquer certaines observations récentes et de faire des prédictions pour des observations futures. / Unveiling the nature of dark matter is one of the greatest challenges of modern physics, at the interface between astrophysics, cosmology and particle physics. In this thesis, I tackle various aspects of indirect searches for dark matter particles, which provide a complementary approach to direct detection or collider experiments. We are now entering into an era of instruments with outstanding capabilities, so it was timely to tackle the problem of the dark matter density profile at the centers of galaxies with novel methods, which motivated this thesis. Taking advantage of these technological advances, I investigate new ways of probing the very central part of dark matter halos, especially focusing on dark matter spikes, i.e. very strong enhancements of the dark matter density that can form around supermassive black holes. I show that we can go beyond standard dark matter searches by studying photon emission from electrons and positrons produced in dark matter annihilation processes. In this context, I describe a new cosmic-ray propagation technique to account for injection by spiky distributions at the centers of galaxies. I develop novel models of the diffuse emission in the central regions of galaxies, focusing not only on the center of the Milky Way, but on the central regions of other galaxies as well. This allows me to explain recently reported observations and make predictions for future observations.

Abstract In this thesis we shed light on the formation and evolution of disk galaxies, which often host a stellar bar (about 2/3 of cases). In particular, we address the bar-driven secular evolution, that is, the steady redistribution of stellar and gaseous material through the disk induced by the bar torques and resonances. We characterize the mass distribution of the disks in the Spitzer Survey of Stellar Structure in Galaxies (S4G, Sheth et al. 2010) and study the properties of the different stellar structure components and the interplay between them. We use 3.6µm photometry for ~ 1300 face-on and moderately inclined disk galaxies to analyze the frequency, dimensions, orientations and shapes of stellar bars, spiral arms, rings, (ring)lenses, and barlenses (i.e. lens-like structures embedded in the bars). We calculate the strength of the bars in the S4G via ellipse fitting, Fourier decomposition of the galaxy images, and from the gravitational tangential-to-radial forces. We also estimate the stellar contribution to the circular velocity, allowing us to analyze the coupling between non-baryonic and stellar matter within the optical disk. We average stellar density profiles (1D), the disk(+bulge) component of the rotation curve, and stellar bars (2D) as a function of fundamental galaxy parameters. We complement the study with integral-field unit kinematic data from Seidel et al. (2015b) for a subsample of 16 S4G barred galaxies. We quantify the bar-induced perturbation strengths in the stellar and gaseous disk from the kinematics, and show that they agree with the estimates obtained from the images. We also use Hα Fabry-Perot observations from Erroz-Ferrer et al. (2015) for 29 S4G disk galaxies to study the inner slope of the rotation curves. We provide possible observational evidence for the growth of bars in a Hubble time. We demonstrate the role of bars causing the spreading of the disk and the enhancement of the central stellar concentration. Our observations support the idea that Boxy/Peanut bulges in face-on perspective manifest as barlenses, that are often identfied in early-type galaxies hosting strong bars, and some of them also as inner lenses. We find that the amount of dark matter within the optical disk scales with the total stellar mass, as expected in the ΛCDM models. We also confirm that the observed inner velocity gradient is correlated with the central surface brightness, showing a strong connection between the inner shape of the potential well and the central stellar density. We show that disks and bars in early-type (T < 5 ≡ Sc) and late-type (T ≥ 5) disk galaxies, or alternatively in galaxies having total stellar masses greater or smaller than 1010M☉, are characterized by very distinct properties. Late-type disks are less centrally concentrated (many galaxies are bulge-less) and present a larger halo-to-stellar mass ratio, what probably affects the disk stability properties. The detection of bars in late-type galaxies is strongly dependent on the identification criteria. On average, bars in early-type spirals (T = 0 − 2) are longer (both in physical units and relative to the disk) and have larger density amplitudes than the intermediate-type spirals (T ≈ 5), and the bar lengths among the latest-types in the S4G are also larger. In comparison to earlier types, the bars in late-type systems show larger tangential-to-radial force ratios. This result holds even when the estimated dark halo effect is included.

This dissertation describes a search for the invisible decays of dark matter particles produced in association with a Z boson, where the latter decays to a charged lepton pair. The dataset for this search includes 13.3 1/fb of collisions recorded in 2015 and 2016 at a centre-of-mass energy of 13 TeV in the ATLAS detector at the Large Hadron Collider in Geneva, Switzerland. The invisible particles manifest themselves as missing transverse momentum, or MET, in the detector, while the charged leptons of interest are electron (e+e-) or muon (mu+mu-) pairs. The models simulated for this study are vector mediated simplified models with Dirac fermionic dark matter particles with couplings g_q = 0.25, g_X = 1 and g_l = 0 . The main background to this analysis, ZZ->llvv, is irreducible, as it shares the same signature as the signal. It is estimated with Monte Carlo simulations including contributions from both qq->ZZ and gg->ZZ production modes. Where possible, other backgrounds are estimated using data-driven techniques and reduced through various selection criteria. The final search is performed by looking for a deviation from the Standard Model background expectation in the MET distribution using two signal regions, e+e- and mu+mu-. This is done using statistical tools to make a likelihood fit and set a 95% confidence level limit as no deviations are found. Limits are placed on the presented model of dark matter for mediator masses up to 400 GeV and for a range of dark matter masses from 1 to ~200 GeV. / Graduate

The presence of dark matter is inferred at scales ranging from rotations of galaxies to imprints in the CMB – the Big Bang after-glow. The nature of dark matter is, however, still unknown as no detection other than the gravitational one has been made. This thesis presents two analyses searching for a neutrino signal from dark matter annihilations in the Milky Way. The first analysis searched for an excess of νμ charged current events with directions from the central region of the dark matter halo and, was focused on low energy events, thus probing low dark matter particle masses. Approximately 319 days of data collected with the 79-string configuration of the IceCube detector was used in the analysis. Despite a large deficit in the number of observed events the data were found to be consistent with background and upper limits were set on <σⱴ>. At the time of the analysis these limits were the strongest set by a neutrino experiment below 100 GeV. The second analysis was performed on a data sample originally used in an unfolding analysis of the atmospheric and astrophysical neutrino spectra. The data consisted of contained cascade events above 1 TeV collected with the 79-string configuration and the completed detector in the 86-string configuration during two years of data-taking. The limits set by this analysis were more constraining by up to a factor of 10 compared to previous IceCube analyses, and the most competitive limits are set assuming a Burkert halo profile. These two analyses prompted the development of a signal subtraction likelihood method to address the problem of signal contamination in background estimates based on scrambled data. Additionally a study concerning future extensions of IceCube in the Gen2 project is presented. The cascade reconstruction performance was examined and compared for different proposed detector extensions.

Orientador: Pedro Cunha de Holanda / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Fisica Gleb Wataghin / Made available in DSpace on 2018-08-14T09:35:59Z (GMT). No. of bitstreams: 1 Motta_MarieleKatherineFaria_M.pdf: 2935959 bytes, checksum: 36090b361909fca742a96d1606e1904d (MD5) Previous issue date: 2009 / Resumo: A formação das estruturas ao longo da história do universo depende crucialmente da competição entre efeitos de matéria não-relativística e relativística. Sabemos que existem mecanismos que convertem os conteúdos de uma em outra. Em particular, a explosão de uma supernova tipo colapso do núcleo converte uma energia correspondente a 99% da energia de ligação da estrela de nêutrons remanescente em neutrinos relativísticos. Nos baseamos neste processo para construir um modelo de conversão de matéria escura em matéria relativisstica que evolui com a história do universo e avaliamos os efeitos dessa conversao sobre a formação de estruturas em grandes escalas / Abstract: The structure formation through the history of the universe crucially depends on the competition between non-relativistic and relativistic matter effects. We know that there are mechanisms which convert the contents of one into the other. Particularly the explosion of a core-collapse supernova converts an energy corresponding to 99% of the gravitational binding energy of the remnant neutron star into relativistic neutrinos. Based on this process we have built a conversion model of dark matter into relativistic matter that evolves throughout the history of the universe and we evaluate the effects of this conversion over the large scale structure formation / Mestrado / Física / Mestra em Física

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.

The advent of laser cooling and optical manipulation for atomic samples revolutionized atomic physics in 1990’s, allowing the creation of new phases of matter, more accurate atomic clocks, and enabling leading candidates for the first functional quantum computer. This could not have been predicted at the time, and is a testament to the value of fundamental research for its own sake. These same laser cooling techniques are now being applied to simple molecular systems with the same revolutionary potential. In this thesis, I will present a range of experiments exploring these schemes in a new class of molecules, the diatomic alkaline earth hydrides. We present the creation and characterization of a bright beam of cold barium hydride molecules, high precision spectroscopy of these samples, as well as optical deflection and transverse cooling. This represents the first laser cooling of a Hydride molecule. This is a crucial step towards the creation of new cold molecular samples for a variety of scientific applications. In the final chapter, I will change gears, and introduce new ideas for the detection of scalar field dark matter. While this variety of dark matter is typically searched for using atomic clocks, I will show that the same coupling also leads to anomalous acceleration of test masses. This acceleration would be detectable using both a network of precision acceleration sensors known as the IGETS network, and by the LIGO observatory. This new technique will compliment existing search strategies, and has higher sensitivity for a wide region of parameter space.

The population and formation of dwarf galaxies, Mr > −14, contain clues about the nature of dark matter. The best place to search for these dwarf galaxies without influence from nearby large galaxies is within galaxy voids, where no galaxies have yet been found. To search for this potential dwarf galaxy population we have developed and applied a new photometric technique. We use three redshifted Ha filters, designated Ha8, Ha12, and Ha16, along with the Sloan broadband filters, g', r', and i' to identify emission line galaxies. From the ratio of the object flux through the Ha filters, Ha12-Ha8 and Ha12-Ha16, we are able to determine the distance to these galaxies and the strength of the emission line captured in the filter set. One problem with using just the three Ha filters is that the system will be sensitive to any emission line which has been redshifted enough to fall within the set. Of particular concern are the [OII] and [OIII] lines which will contaminate the sample. To overcome this we use a color-color relation, g' - r' and r' - i', to help separate which type of emission has been detected. We have applied this method to search for galaxies within the void FN2 and FN8. From this we have found 23 candidate objects which could have Ha emission placing them inside of the void. To better understand the population density dwarf galaxies through voids we have also modeled the population of objects which we will detect having Ha emission compared to the contamination of back ground objects which we can then use to compare the density in the void with the mean galaxy density. We have also begun taking spectra of the emission objects, to ensure our method does detect emission line objects, to test how well the distance and emission strength determination is, and to begin identifying which type of emission we have detected. To date we have taken spectra on 6 objects. All 6 showed emission, 4 with [OII] and 2 with [OIII]. Though none was Ha we formed a “pseudo-redshift” to determine the accuracy of our measurements. This shows that our method is accurate to -127+-204 km/sec.