Mémoire numérisé par la Division de la gestion de documents et des archives de l'Université de Montréal

Weak-scale supersymmetry is one of the most favoured theories beyond the Standard Model of particle physics that elegantly solves various theoretical and observational problems in both particle physics and cosmology. In this thesis, I describe the theoretical foundations of supersymmetry, issues that it can address and concrete supersymmetric models that are widely used in phenomenological studies. I discuss how the predictions of supersymmetric models may be compared with observational data from both colliders and cosmology. I show why constraints on supersymmetric parameters by direct and indirect searches of particle dark matter are of particular interest in this respect. Gamma-ray observations of astrophysical sources, in particular dwarf spheroidal galaxies, by the Fermi satellite, and recording nuclear recoil events and energies by future ton-scale direct detection experiments are shown to provide powerful tools in searches for supersymmetric dark matter and estimating supersymmetric parameters. I discuss some major statistical issues in supersymmetric global fits to experimental data. In particular, I further demonstrate that existing advanced scanning techniques may fail in correctly mapping the statistical properties of the parameter spaces even for the simplest supersymmetric models. Complementary scanning methods based on Genetic Algorithms are proposed. / At the time of the doctoral defense, the following paper was unpublished and had a status as follows: Paper 4: Submitted.

Ένα από τα μεγαλύτερα θεωρητικά κατασκευάσματα της φυσικής είναι αυτό της σκοτεινής ύλης. Στην παρούσα μεταπτυχιακή διπλωματική εργασία αναλύονται οι λόγοι για τους οποίους πιστεύουμε στην ύπαρξη της σκοτεινής ύλης, τα σωματίδια και γενικά τα αντικείμενα που μπορεί να την απαρτίζουν, η σκοτεινή ενέργεια και οι μορφές της και τέλος εναλλακτικές προτάσεις. / One of the most important theoretical creations of physics is dark matter. In this master thesis we describe the reasons we believe in the existence of dark matter, the particles and the objects that consists dark matter, dark energy and finally alternative theories.

Cette thèse présente la recherche de nouvelle physique avec un état final contenant un seul photon et de l'énergie transverse manquante. On recherche la matière sombre (ou noire) et la signature de particules supersymétriques. L'analyse des données collectées par le détecteur ATLAS au LHC, issues de collisions proton-proton dont l'énergie dans le centre de masse est de 8 TeV, est faite avec une luminosité intégrée de 20.3fb−1. L'accord entre les données mesurées et les prédictions du modèle standard permet d'établir une limite sur la section effi- cace de production mesurable. Cette limite est observée à la valeur de 3.64 fb à 95% de niveau de confiance.Dans cette thèse, la limite expérimentale obtenue est également interprétée comme une limite dans l'espace des paramètres de deux nouveaux modèles.Le premier est basé sur une théorie des champs effective qui s'inspire des résultats du satellite Fermi-LAT. Dans ce modèle, les particules de matière sombre se couplent aux pho- tons par une interaction de contact. Les limites sur l'échelle de masse effective sont établies et dépendent d'un postulat sur les constantes de couplage. Elles contraignent l'espace des paramètres qui est compatible avec les résultats de Fermi-LAT.Le second est un modèle supersymétrique simplifié décrivant la production de paires de squarks se désintégrant en un quark et un neutralino. Dans ce cas, le photon est émis soit dans l'état initial soit dans l'état final. De plus, le spectre en masse est compressé, i.e. que la différence de masse entre les squarks et les neutralinos est supposée petite. Les limites sont établies sur la section efficace de production. Ces limites montrent une exclusion sur la masse des squarks jusqu'à 250 GeV dans la région la plus compressée de l'espace des paramètres. Le photon pouvant être émis par le squark intermédiaire, cet état final pourrait permettre de déterminer la charge du squark.Enfin, une étude préliminaire prospective à l'énergie de collision de 13 TeV a égale- ment été menée. Elle montre qu'avec 5fb−1 de données seulement, les limites peuvent être améliorées de 10%. / This thesis presents the search for new physics in the final state containing a single photon and missing transverse momentum. The analysis is performed on 20.3fb−1 of proton-proton collisions data at a center-of-mass energy of 8 TeV collected by the ATLAS detector at the Large Hadron Collider. Given the good agreement of the data with the Standard Model pre- diction of such events, an upper limit to the visible cross section produced by new physics is derived. The observed limit at 95% confidence level is 3.64 fb.In this thesis, the results are also interpreted as limits in the parameter space of two new physics models. The first model is an effective field theory, inspired by Fermi-LAT results, in which dark matter particles couple to photons via a contact interaction vertex. Limits are set on the effective mass scale and depend on the postulated coupling constants. The limits set in this dark matter model provide an effective constraint in the parameter space of the theory compatible with the Fermi-LAT results. The second one is a simplified supersymmetric model describing squark pair production with their subsequent decay into a quark and a neutralino. The photon is emitted as initial or final state radiation and the spectrum is compressed, i.e. the mass difference between the squark and the neutralino is assumed to be small. Limits are set on the production cross-section; squark masses are excluded up to 250 GeV in the very compressed region. As the photon can be irradiated from the intermediate squark, this final state would eventually provide the possibility to probe the charge of the squark.A preliminary study has also been carried out to show the search sensitivity with 13 TeV data, which indicate that the limits presented in this thesis can already be improved by 10% with 5fb−1.

[pt] O Modelo Padrão é uma das teorias mais bem sucedidas da física de partículas. Com a descoberta do bóson de Higgs, além de ter sido uma demonstração robusta do poder preditivo do Modelo Padrão, foi aberto um novo caminho para a investigação de nova física interagindo por meio do portal de Higgs, incluindo cenários motivados por matéria escura e bariogênese. Investigamos a estabilidade do potencial e os pólos de Landau do Modelo Padrão sob efeito da interação entre o bóson de Higgs e uma partícula escalar. Focamos no regime onde os escalares são gerados primariamente via um off-shell Higgs. Prevemos o espaço de parâmetros disponível para acessar a teoria em diferentes valores de massa do campo escalar. / [en] The Standard Model is one of the most successful theories in particle physics. With the discovery of the Higgs boson, a new pathway has been opened to investigate possible new physics interacting through the Higgs portal, including scenarios motivated by dark matter and baryogenesis. Supposing there is a neutral scalar state in the Standard Model coupled to it only through the Higgs portal, we investigate the potential stability and the Landau poles of the extended Standard Model potential. We focus on the regime in which the scalars are primarily generated via an off-shell Higgs. We predict the available parameter space to probe the theory for different mass values.

Le Modèle Standard Supersymétrique Minimal (MSSM), le plus étudié des modèles de Nouvelle Physique, contient un candidat à la matière noire : le neutralino. Un des mécanismes qui permet de réduire la densité relique de neutralino jusqu'à l'intervalle expérimental de WMAP et de Planck est la coannihilation entre le neutralino et le stop. Dans cette thèse nous étudions deux aspects différents liés à la prédiction de la densité relique dans la région de coannihilation neutralino-stop, ainsi qu'au calcul des sections efficaces d'annihilation et de coannihilation correspondantes. Nous présentons tout d'abord la matière noire en tant que WIMP ainsi que le Modèle Standard de la Physique des Particules, puis nous abordons le MSSM ainsi la phénoménologie de la densité relique de neutralino. Nous étudions ensuite la phénoménologie de la violation de saveur non minimale dans le secteur des squarks dans le contexte de la densité relique de neutralino. Nous considérons des termes violant la saveur dans le secteur des squarks up et down de chiralité droite et de troisième génération et montrons qu'ils peuvent avoir un impact important sur les sections efficaces d'annihilation et de coannihilation du neutralino, et en conséquence sur la densité relique. Finalement, nous nous intéressons à la possibilité d'améliorer la précision avec laquelle la densité relique est prédite, en calculant les sections efficaces d'annihilation et de coannihilation à l'ordre supérieur dans la théorie des perturbation. En se basant sur des travaux antérieurs qui ont montré que l'impact des corrections SUSY-QCD à une boucle pour l'annihilation de neutralino était supérieur à l'incertitude expérimentale, nous avons calculé de telles corrections dans le cas de la coannihilaiton neutralino-stop en bosons de jauge électrofaibles et bosons de Higgs. / The Minimal Supersymmetric Standard Model (MSSM), the most famous model of Physics beyond the Standard Model, provides a good dark matter candidate: the neutralino. One of the mechanisms which can reduce the predicted relic density of neutralino to the experimental range of WMAP and Planck is the coannihilation between the neutralino and the stop. In this thesis, we study two different aspects related to the prediction of the relic density in the neutralino-stop coannihilation region and the calculation of the corresponding annihilation and coannihilation cross sections. We first make short reviews of WIMP dark matter and the Standard Model of particle Physics, introduce the MSSM and discuss the phenomenology of neutralino relic density. We then study the phenomenology of Non Minimal Flavor Violation in the squark sector in the context of neutralino relic density. We consider flavor violating terms in the sectors of right handed third generation up and down squarks and show that they can have an important impact on the thermally averaged (co)annihilation cross section of the neutralino, and therefore on its relic density. Finally, we focus on the issue of improving the precision with which the relic density is calculated, by computing (co)annihilation cross sections at Next-to-Leading Order. Following earlier work in the calculation of one-loop SUSY-QCD corrections to the annihilation of neutralinos, which have shown that the impact of such corrections was larger than the experimental uncertainty, we have calculated similar corrections for the neutralino-stop coannihilation into electroweak gauge and Higgs bosons.

Submitted by Vasti Diniz (vastijpa@hotmail.com) on 2017-09-13T13:01:16Z No. of bitstreams: 1 arquivototal.pdf: 7899614 bytes, checksum: f001983854e55609b8ccfb1ce80578f2 (MD5) / Made available in DSpace on 2017-09-13T13:01:16Z (GMT). No. of bitstreams: 1 arquivototal.pdf: 7899614 bytes, checksum: f001983854e55609b8ccfb1ce80578f2 (MD5) Previous issue date: 2015-02-27 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / One of the main problems that permeates the Particle Physics and Cosmology is the Dark Matter (DM), which makes up about 26% of the energy content of the Universe. The main evidence pointing to its existence provides us with important features, such as being neutral, stable (with lifetime over the age of the Universe), cold or warm, weakly interacting with Particle Physics Standard Model (SM) particles and sufficiently abundant. The SM does not provide a candidate who meets these characteristics and hence it is necessary to extend it. One of the most sophisticated extensions of the SM is the Supersymmetry, that in addition to solving the problem of DM, explains other unsolved puzzles that are present in SM, among them, the hierarchy and the unification of the gauge couplings. This model implies the inclusion of a new symmetry that puts bosons and fermions in equal footing. The minimal supersymmetric version of the SM is the Minimal Supersymmetric Standard Model (MSSM), whose viable candidate is the neutralino, which is a fermion composed of superpartners of neutral Higgs and gauge bosons. In this work, we performed the neutralino analysis as DM candidate in CMSSM or mSUGRA scenario, which contains 5 free parameters, M0, M1/2, tan , sign(μ) and A0, for two different analyzes. In the first one we varied the M0 and M1/2 parameters for three different values of tan while in the second and third one we varied all parameters except the sign(μ). In this study, we use some computational tools, including, SARAH, SPheno, SSP and Micromegas, in order to obtain DM Relic Abundance and DM scattering cross section in this scenario. We compared our results with the most recent experimental data, namely, we have used Planck satellite data for the relic abundance, LUX and XENON1T (prospect) for the spin-independent scattering cross section and XENON100 for the spin dependent one. We finally analyzed the implications concerning the viability of the MSSM under the light of the DM problem. / Um dos principais problemas que permeia a Física de Partículas e Cosmologia é a Matéria Escura (ME), que compõe cerca de 26% do conteúdo energético do Universo. As principais evidências que apontam para a sua existência nos fornecem importantes características, tais como, ser neutra, estável (com tempo de vida maior que a idade do Universo), fria ou morna, pouco interagente com partículas do Modelo Padrão de Física de Partículas (MP)e suficientemente abundante. O MP não fornece um candidato que supre estas características, sendo necessário estendê-lo. Uma das mais sofisticadas extensões do MP é a Supersimetria, que além de resolver o problema da ME, soluciona outros que estão presentes no MP, dentre eles, a hierarquia e a unificação dos acoplamentos de gauge. Tal modelo implica na inclusão de uma nova simetria que coloca bósons e férmions em pé de igualdade. A versão mínima supersimétrica do MP é o Modelo Padrão Supersimétrico Mínimo (MSSM), cujo candidato viável à ME é o neutralino, que se trata de um férmion composto pelos superparceiros dos bósons de gauge e Higgs neutros. Neste trabalho, fizemos uma análise do neutralino como candidato à ME no cenário CMSSM ou mSUGRA, que contém 5 parâmetros livres, M0, M1/2, tan , sinal(μ) e A0, para três análises distintas. Na primeira variamos apenas os parâmetros M0 e M1/2 para três valores distintos da tan e na segunda e terceira variamos todos os parâmetros com exceção do sinal(μ). Neste estudo, utilizamos algumas ferramentas computacionais, entre as quais, SARAH, SPheno, SSP e micrOMEGAs, no intuito de obter abundância e seção de choque de espalhamento de ME neste cenário. Obtidos os gráficos, comparamos com os resultados experimentais mais recentes, para a abundância utilizamos dados do satélite Planck, para a seção de choque de espalhamento independente de spin, o LUX e XENON1T (2017) e para dependente de spin, XENON100 e verificamos suas implicações na viabilidade do modelo.

Made available in DSpace on 2014-12-17T15:14:57Z (GMT). No. of bitstreams: 1 HidalynTC_TESE.pdf: 3025002 bytes, checksum: 560b594294d11c4905312394b1d53359 (MD5) Previous issue date: 2012-02-16 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior / We investigate the cosmology of the vacuum energy decaying into cold dark matter according to thermodynamics description of Alcaniz & Lima. We apply this model to analyze the evolution of primordial density perturbations in the matter that gave rise to the first generation of structures bounded by gravity in the Universe, called Population III Objects. The analysis of the dynamics of those systems will involve the calculation of a differential equation system governing the evolution of perturbations to the case of two coupled fluids (dark matter and baryonic matter), modeled with a Top-Hat profile based in the perturbation of the hydrodynamics equations, an efficient analytical tool to study the properties of dark energy models such as the behavior of the linear growth factor and the linear growth index, physical quantities closely related to the fields of peculiar velocities at any time, for different models of dark energy. The properties and the dynamics of current Universe are analyzed through the exact analytical form of the linear growth factor of density fluctuations, taking into account the influence of several physical cooling mechanisms acting on the density fluctuations of the baryonic component of matter during the evolution of the clouds of matter, studied from the primordial hydrogen recombination. This study is naturally extended to more general models of dark energy with constant equation of state parameter in a flat Universe / Investigamos a cosmologia da energia do v?cuo decaindo em mat?ria escura fria de acordo com a descri??o termodin?mica de Alcaniz & Lima. Aplicamos esse modelo na an?lise da evolu??o de perturba??es de densidade primordiais na mat?ria que deram origem a primeira gera??o de estruturas ligadas pela gravidade no Universo, os chamados Objetos da Popula??o III. A an?lise da din?mica desses sistemas envolver? o c?lculo de um sistema de equa??es diferenciais que governam a evolu??o de perturba??es para o caso de dois fluidos acoplados (mat?ria escura e mat?ria bari?nica), modelados com um perfil Top-Hat baseado na perturba??o das equa??es da hidrodin?mica, uma ferramenta anal?tica eficiente para estudar as propriedades dos modelos de energia escura, como o comportamento do fator de crescimento linear e o ?ndice de crescimento, grandezas f?sicas intimamente relacionadas aos campos de velocidades peculiares em qualquer ?poca, para diferentes modelos de energia escura. As propriedades e a din?mica do Universo atual s?o analisadas atrav?s da forma anal?tica exata do fator de crescimento linear de flutua??es de densidade, levando em considera??o a influ?ncia de v?rios mecanismos f?sicos de esfriamento atuando sobre as flutua??es de densidade da componente bari?nica da mat?ria durante a evolu??o das nuvens de mat?ria, estudadas desde a recombina??o primordial do hidrog?nio. Esse estudo ? naturalmente estendido aos modelos mais gerais de energia escura com o par?metro da equa??o de estado constante em um Universo plano

Made available in DSpace on 2014-12-17T15:15:05Z (GMT). No. of bitstreams: 1 HidalynTCMS.pdf: 3137452 bytes, checksum: c9101961e25b2af76cdd7d74bfe14bb5 (MD5) Previous issue date: 2007-04-26 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior / Understanding the way in which large-scale structures, like galaxies, form remains one of the most challenging problems in cosmology today. The standard theory for the origin of these structures is that they grew by gravitational instability from small, perhaps quantum generated, ?uctuations in the density of dark matter, baryons and photons over an uniform primordial Universe. After the recombination, the baryons began to fall into the pre-existing gravitational potential wells of the dark matter. In this dissertation a study is initially made of the primordial recombination era, the epoch of the formation of the neutral hydrogen atoms. Besides, we analyzed the evolution of the density contrast (of baryonic and dark matter), in clouds of dark matter with masses among 104M? ? 1010M?. In particular, we take into account the several physical mechanisms that act in the baryonic component, during and after the recombination era. The analysis of the formation of these primordial objects was made in the context of three models of dark energy as background: Quintessence, ?CDM(Cosmological Constant plus Cold Dark Matter) and Phantom. We show that the dark matter is the fundamental agent for the formation of the structures observed today. The dark energy has great importance at that epoch of its formation / Entender o modo pelo qual estruturas em grande-escala, como gal?xias, se formam permanece um dos problemas mais desafiadores em cosmologia hoje. A teoria padr?o para a origem destas estruturas ? que elas cresceram por instabilidade gravitacional de pequenas, talvez geradas quanticamente, flutua??es na densidade de mat?ria escura, b?rions e f?tons sobre um Universo primordial uniforme. Depois da recombina??o, os b?rions come?aram a cair nos po?os de potencial gravitacional pr?-existentes de mat?ria escura. Nesta disserta??o ? feito inicialmente um estudo da era da recombina??o primordial, a ?poca da forma??o dos ?tomos de hidrog?nio neutro. Al?m disso, analisamos a evolu??o do contraste de densidade (de mat?ria bari?nica e escura), em nuvens de mat?ria escura com massas entre milhares e bilh?es de massas solares. Em particular, na an?lise da componente bari?nica, levamos em conta os v?rios mecanismos f?sicos que ocorrem nela durante e depois da era da recombina??o. A an?lise da forma??o desses objetos primordiais foi feita no contexto de tr?s modelos de energia escura como background ': Quintess?ncia, CDM (Constante Cosmol?gica mais Mat?ria Escura Fria) e Fantasma. Mostramos que a mat?ria escura ? o agente fundamental para forma??o das estruturas observadas hoje. A energia escura tem grande import?ncia na ?poca de sua forma??o

Capture-évolution-éjection de particules par des systèmes binaires (étoile-planète, étoile binaire, étoile-trou noir supermassif, trou noir binaire, ...). Dans une première partie, en utilisant une généralisation de l'application de Kepler, nous décrivons, au travers du cas de 1P/Halley, la dynamique chaotique des comètes dans le système solaire. Le système binaire, alors considéré, est composé du Soleil et de Jupiter. L'application symplectique utilisée permet de rendre compte des différentes caractéristiques de la dynamique : trajectoires chaotiques, îlots invariants de KAM associés aux résonances avec le mouvement orbital de Jupiter,... Nous avons déterminé de façon exacte et semi-analytique l'énergie échangée (fonction kick) entre le système solaire et la comète de Halley à chaque passage au périhélie. Cette fonction kick est la somme des contributions des problèmes à trois corps Soleil-planète-comète associés aux 8 planètes du système solaire. Nous avons montré que chacune de ces contributions peut être décomposée en un terme keplerien associé au potentiel gravitationnel de la planète et un terme dipolaire dû au mouvement du soleil autour du centre de masse du système solaire. Dans une deuxième partie, nous avons utilisé la généralisation de l'application de Kepler pour étudier la capture de particules de matière noire au sein des systèmes binaires. La section efficace de capture a été calculée et montre que la capture à longue portée est bien plus efficace que la capture due aux rencontres proches. Nous montrons également l'importance de la vitesse de rotation du système binaire dans le processus de capture. Notamment, un système binaire en rotation ultrarapide accumulera en son sein une densité de matière jusqu'à 10^4 fois celle du flot de matière le traversant. Dans la dernière partie, en intégrant les équations du mouvement du problème à trois corps restreint plan, nous avons étudié l'éjection des particules capturées par un système binaire. Dans le cas d'un système binaire dont les deux corps sont de masses comparables, alors que la majorité des particules sont éjectées immédiatement, nous montrons, sur les sections de Poincaré, que la trace des particules restant indéfiniment aux abords du système binaire forme une structure fractale caractéristique d'un répulseur étrange associé à un système chaotique ouvert. Cette structure fractale, également présente dans l'espace réel, a une forme de spirale à deux bras partageant des similitudes avec les structures spiralées des galaxies comme la nôtre. / This work is devoted to the study of the restricted 3-body problem and particularly to the capture-evolution-ejection process of particles by binary systems (star-planet, binary star, star-supermassive black hole, binary black hole, ...). First, using a generalized Kepler map, we describe, through the case of 1P/Halley, the chaotic dynamics of comets in the Solar System. The here considered binary system is the couple Sun-Jupiter. The symplectic application we use allows us to depict the main characteristics of the dynamics: chaotic trajectories, KAM islands associated to resonances with Jupiter orbital motion, ... We determine exactly and semi-analytically the exchange of energy (kick function) between the Solar System and 1P/Halley at its passage at perihelion. This kick function is the sum of the contributions of 3-body problems Sun-planet-comet associated to the eight planets. We show that each one of these contributions can be split in a keplerian term associated to the planet gravitational potential and a dipolar term due to the Sun movement around Solar System center of mass. We also use the generalized Kepler map to study the capture of dark matter particles by binary systems. We derive the capture cross section showing that long range capture is far more efficient than close encounter induced capture. We show the importance of the rotation velocity of the binary in the capture process. Particularly, a binary system with an ultrafast rotation velocity accumulates a density of captured matter up to 10^4 times the density of the incoming flow of matter. Finally, by direct integration of the planar restricted 3-body problem equations of motion, we study the ejection of particles initially captured by a binary system. In the case of a binary with two components of comparable masses, although almost all the particles are immediately ejected, we show, on Poincaré sections, that the trace of remaining particles in the vicinity of the binary form a fractal structure associated to a strange repeller associated to chaotic open systems. This fractal structure, also present in real space, has a shape of two arm spiral sharing similarities with spiral structures observed in galaxies such as the Milky Way.