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Ce manuscrit présente une mesure de la section efficace de production des bosons W et de l'asymétrie de charge dans les collisions proton-proton avec l'expérience ATLAS à une énergie dans le centre de masse de 7 TeV. Ces mesures posent des contraintes sur la fraction d'impulsion des protons portée par les partons qui contribuent à la production des bosons W et donc elles permettent d'ameliorer notre compréhension des fonctions de distribution de partons. Dans l'analyse, les événements de signal sont sélectionnés dans le canal électronique W −→eν . Le calorimètre électromagnétique à Argon Liquide joue un rôle important pour la détection des électrons. L'auteur de cette thèse a travaillé sur la reconstruction en ligne de l'énergie dans les détecteurs à LAr. Un aspect important pour les mesures liées à la charge électrique, comme l'asymétrie de charge du boson W, est l'évaluation du taux de misidentification de la charge pour des électrons et des positons. Dans ce manuscrit, la section efficace de production de bosons W multipliée par le rapport de branchement est présentée de façon inclusive, en fonction de la pseudorapidité du lepton, et comme mesure différentielle en deux dimensions (c'est à dire en fonction de la pseudorapidité et de l'énergie transverse du lepton). La mesure de l'asymétrie de charge est aussi présentée en fonction de la pseudorapidité du lepton uniquement et en fonction de la pseudorapidité et de l'énergie transverse du lepton. Les données ont été enregistrées par l'expérience ATLAS en 2011 et correspondent à 4.7 fb−1 .

This thesis is concerned with the study of cosmic strings. We studied the values for the Higgs mass and string coupling for which the gravitational effect of an infinite cosmic string in the context of the Einstein theory is not only locally but also globally weak. We conclude this happens for strings formed at scales less or equal to the Planck one with Higgs mass being less or equal to the boson vectorial mass. Then we examined the metric of an isolated self-gravitating abelian-Higgs vortex in dilatonic gravity for arbitrary coupling of the vortex fields to the dilaton. We looked for solutions in both massless and massive dilaton gravity. We compared our results to existing metrics for strings in Einstein and .Jordan-Brans-Dicke theories. We explored the generalisation of Bogomolnyi arguments for our vortices and commented on the effects on test particles. We then included the presence of an axion field and examined the metric of an isolated self-gravitating axionic-dilatonic string. Finally we studied dilatonic strings through black hole solutions in string theory. We concluded that the horizon of non-extreme charged black holes supports the long-range fields of the Nielsen-Olesen string that can be considered as black hole hair and whose gravitational effect is in general the production of a conical deficit into the metric of the black hole background. We also concluded that the effect of the dilaton on the horizon of these black holes is to generate an additional charge.

Strongly correlated systems on geometrically frustrated lattices can stabilize a large number of interesting phases that includes a wide array of novel Mott insulators in both bosonic and electronic systems. Charge fluctuations in a Mott insulator are suppressed due to strong mutual interaction among the particles. The presence of frustration is of particular importance as the physics it offers is often rich, unexpectedly complicated, and continues to raise many open questions. The thesis elucidates some of these issues on a kagome lattice where strong interactions among the particles in the Mott phase impose non-trivial local constraints depending on the filling fraction on the lattice. These Mott insulators, in addition to featuring unusual magnetic and/or charge ordering, can also harbor topologically ordered states of quantum matter, e.g., resonating valence bond liquids realized in certain quantum dimer models on non-bipartite lattices. The dimer models can be regarded as low-energy effective theories for different types of bosonic models in the strong-coupling limit. Exploring this connection is a central theme of this thesis with the aim of realizing novel strongly correlated ground states. Past studies of these models have revealed the existence of various ordered and disordered phases with distinct signatures. Among these low-energy phases, the presence of a stable topological liquid at a particular point, known as Rokhsar-Kivelson point, in the phase diagram is notable. The classical versions of the dimer model are also known to have garnered a vast interest in various fields ranging from problems of pure mathematical origin to ones in physical chemistry as well as statistical physics. Pioneered by Kasteleyn, several analytical works came forward to exactly calculate the partition function of the problem from which other physical observables can be derived. Classical numerical methods are extensively applied to these models to verify the analytical predictions. We introduce a new classical algorithm here to compute the correlation functions of a classical dimer model on a square (bipartite) and a triangular (non-bipartite) lattice based on a tensor network construction. The method, called tensor network renormalization group, turns out to be a powerful tool for simulating short-ranged gapped systems as inferred from our results benchmarked against the classical Monte-Carlo technique and compared with past analytical studies. One should note that the quantum dimer model at the Rokhsar-Kivelson point can also be described as an infinite temperature canonical ensemble of classical dimers because of the particular structure of the ground state which is an equal weight superposition in the configuration manifold. The geometry of the lattice plays a pivotal role in deciding the nature of the phases that arise in the dimer models. Many physical properties of the dimer liquid phase can be extracted in the simple classical setting which certainly allows for a deep understanding of the classical models to be developed. The liquid phase is gapped on non-bipartite lattices and gapless on bipartite lattices, which is reflected in the decay of correlation functions with spatial distances. In general on non-bipartite lattices, the topological nature of the dimer liquid is characterized by a Z2 topological order which survives even when the model is perturbed away from the Rokhsar-Kivelson point. Stability of this liquid phase not only depends on the lattice geometries but notably on dimer concentrations also. In this context, we focus on a particular variant of the dimer model on a triangular lattice which is known as the quantum fully packed loop model. The model is composed of nonintersecting closed loops made of dimers and governed by the same Hamiltonian as the quantum dimer model. The loop model provides an effective low-energy description of a strongly correlated bosonic system at 1/3 filling on the kagome lattice. The corresponding Bose-Hubbard Hamiltonian consists of nearest-neighbor hopping and all possible repulsive interactions within a hexagonal plaquette. Conspicuous features of the zero-temperature phase diagram for this model include (i) presence of a stable Z2 liquid even without any Rokhsar-Kivelson potential term (in distinction to the standard quantum dimer model), and (ii) an unconventional phase transition from the liquid phase to a novel crystalline phase that has nematic order (dubbed lattice nematic). For a deeper understanding of the physics, a mapping to an Ising gauge theory is presented. The gauge theoretic description provides a useful way to predict the nature of the quantum phase transition to lie in the O(3) universality class. Finally a fermionic model at the same 1/3 filling is considered in which the ground state exhibits a number of exotic local orderings resulting from the spin-charge interplay of electrons. The Hamiltonian comprises nearest-neighbor hopping, strong on-site Coulomb interaction, and repulsive interaction terms only between nearest-neighbors. In the strong correlation limit, this fermionic problem maps to a two-color fully packed loop model – a model in which the loop segments carry an additional quantum number as color on a honeycomb lattice. The effective theory is governed by coherent three-particle ring exchanges and nearest-neighbor antiferromagnetic spin exchanges. The competition between these two leads to a phase diagram composed of a novel plaquette ordered state (known as the plaquette phase) that undergoes phase transition to a new kind of charge ordered state which we call a short loop phase. From our numerical analysis, we conclude that the plaquette phase features an unusual antiferromagnetic order with gapless spin excitations while the charge-ordered state is subjugated by spin fluctuations of localized electrons arranged in small hexagonal loops on the kagome lattice.

Made available in DSpace on 2014-06-11T19:25:30Z (GMT). No. of bitstreams: 0 Previous issue date: 2005-03Bitstream added on 2014-06-13T18:53:34Z : No. of bitstreams: 1 cardona_sah_me_ift.pdf: 677122 bytes, checksum: ef4eda2c094c5339bde81ff781b3d4cd (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / A supersimetria é um tópico importante na física teórica atual. Em particular, tem-se dedicado grande esforço no estudo das extensões supersimétricas do Modelo Padrão (SM) desde a década de 80. A incorporação da supersimetria no SM resulta em uma grande quantidade de modelos. O modelo com o conteúdo mínimo de partículas assim como de interações é chamado o Modelo Mínimo Supersimétrico (MSSM). DEvido à supersimetria, todos os modelos supersimétricos apresentam diferenças com relação ao SM. A principal delas, além do conteúdo de partículas, está no setor de Higgs. Em particular, o setor de Higgs do modelo MSSM contem cinco graus de liberdade (cinco bósons de Higgs), diferentemente do SM, que contem apenas um bóson de Higgs. Outra diferença importante no caso do MSSM deve-se à mistura dos estados associados pela supersimetria aos bósons de Gauge e aos bósons de Higgs, chamados gauginos e higgsinos respectivamente, cujos autoestados de massa são conhecidos como charginos e neutralinos. Estas partículas desempenham um papel fundamental na possível descoberta da supersimetria na escala de energia de TeV's. / Supersymmetry is a fundamental topic in the actual theoretical physics. In particular, since the 80's, huge efforts have been done studying the supersymmetric extensions of the Standard Model (SM). Including supersymmetry in the SM generates a great amount of models. Among all of these, there is one that involves the minimum number of particles and interactions. This model is known as the Minimal Supersymmetric Standard Model (MSSM). Due to the incorporation of supersymmetry, all the extensions have differences in relation with the SM. The most remarkable one, beyond the particles content, lies in the Higgs sector. Particularly, in the MSSM Higg's sector there are five degrees of freedom (five Higgs bosons), in contrast with the SM (just one). Another difference is related wit the higgsino and gaugino mixture. This result in the presence of mass eigenstates known as charginos and neutralinos. The later particles play a fundamental role in the possible test of supersymmetry at the TeV's scales.

Made available in DSpace on 2015-07-13T12:10:09Z (GMT). No. of bitstreams: 0 Previous issue date: 2015-03-09. Added 1 bitstream(s) on 2015-07-13T12:25:43Z : No. of bitstreams: 1 000833427.pdf: 449220 bytes, checksum: 758ad7ad483cbe265ba29cfb939252ad (MD5) Bitstreams deleted on 2016-05-04T13:08:32Z: 000833427_.pdf,. Added 1 bitstream(s) on 2016-05-04T13:09:34Z : No. of bitstreams: 1 000833427.pdf: 27828302 bytes, checksum: f9bffd8775ba9e024fb2915e6e0a6087 (MD5) / O objetivo deste trabalho é estudar os aspectos gerais do setor escalar do Modelo Padrão, a partir princípio de gauge, que dá consistência teórica à formulação do Modelo Eletrofraco, assim como a quebra espontânea de simetria e o mecanismo de Higgs que são fundamentais no contexto do modelo para a geração de massa das partículas elementares e, tem como consequência o surgimento de uma nova partícula escalar massiva, o bóson de Higgs do Modelo Padrão, cuja massa não está definida no modelo. Apresentamos um estudo dos principais modos de produção e decaimento do bóson de Higgs bem como a sua busca em aceleradores. Apresentamos um conjunto de resultados experimentais que foram publicados ao longo dos anos nas principais colaborações como LEP, Tevatron e LHC, que contribuíram na longa trajetória da busca, até sua identificação em 2012 / The objective of this work is to study the general aspects of the scale sector of the Standard Model the principle of gauge, which gives theoretical consistency to the electroweak model formulation, as well as spontaneous symmetry breaking and the Higgs mechanism, that are fundamental for the mass generation of the elementary particles, and gives rise to a new massive particle scale, the Higgs boson of whose value is not defined in the model. We present a study of the major modes of production and decay of Higgs boson as well as search of such particle in accelerators. We present a set of experimental results that have been published over the years in the major collaborations as LEP, Tevatron and LHC, which contributed in the long history of the Higgs boson search, until its identification in 2012

Orientador: Fernando Luis de Campos carvalho / Banca: Julio Marny Hoff da Silva / Banca: José Abdalla Helayël-Neto / Resumo: O objetivo deste trabalho é estudar os aspectos gerais do setor escalar do Modelo Padrão, a partir princípio de gauge, que dá consistência teórica à formulação do Modelo Eletrofraco, assim como a quebra espontânea de simetria e o mecanismo de Higgs que são fundamentais no contexto do modelo para a geração de massa das partículas elementares e, tem como consequência o surgimento de uma nova partícula escalar massiva, o bóson de Higgs do Modelo Padrão, cuja massa não está definida no modelo. Apresentamos um estudo dos principais modos de produção e decaimento do bóson de Higgs bem como a sua busca em aceleradores. Apresentamos um conjunto de resultados experimentais que foram publicados ao longo dos anos nas principais colaborações como LEP, Tevatron e LHC, que contribuíram na longa trajetória da busca, até sua identificação em 2012 / Abstract: The objective of this work is to study the general aspects of the scale sector of the Standard Model the principle of gauge, which gives theoretical consistency to the electroweak model formulation, as well as spontaneous symmetry breaking and the Higgs mechanism, that are fundamental for the mass generation of the elementary particles, and gives rise to a new massive particle scale, the Higgs boson of whose value is not defined in the model. We present a study of the major modes of production and decay of Higgs boson as well as search of such particle in accelerators. We present a set of experimental results that have been published over the years in the major collaborations as LEP, Tevatron and LHC, which contributed in the long history of the Higgs boson search, until its identification in 2012 / Mestre

Dans une série de travaux Zied Ammari et Francis Nier ont développé des méthodes pour étudier la dynamique de champ moyen bosonique pour des états quantiques généraux pouvant présenter des corrélations. Ils ont obtenu des formules pour décrire la dynamique des corrélations, ou plus généralement des matrices densité réduites d'ordre arbitraire. Cette thématique a été largement développée ces dernières années. Norbert Mauser en a été un des contributeurs, ainsi que sur la notion de mesure de Wigner qui est la clé de l'analyse développée par Z. Ammari et F. Nier. En général, il est admis que l'asymptotique de champ moyen est une bonne approximation du problème à N particules quand N dépasse la dizaine. Cela concerne l'asymptotique de la matrice densité réduite à une particule qui ne décrit pas la dynamique des corrélations. Un objectif est de tester la validité de la dynamique de champ moyen pour les matrices densité réduites à 2-particules. Pour des tests numériques, les modèles discrets qui n'ont pas été vraiment traités en détail dans les travaux précédents de Z. Ammari et F. Nier semblent bien adaptés. La thèse comprendra donc plusieurs étapes: adapter les résultats précédents de Z. Ammari et F. Nier à des modèles discrets , développer des méthodes numériques pour des systèmes simples mais pertinents, permettant de valider l'approximation de champ moyen et les formules pour la dynamique des corrélations. Au niveau numérique, on utilise des schémas numériques symplectiques, développés spécifiquement ces dernières années pour la discrétisation des équations hamiltoniennes. Une dernière étape concerne la combinaison des deux asymptotiques, champ moyen et approximation des modèles continus par les modèles discrets. / In a serie of works Z. Ammari and F. Nier developed methods to study the dynamics of bosonic mean field for general quantum states which can present correlations. They obtained formulas to describe the dynamics of the correlations, or more generally reduced density matrices with an arbitrary order. This topic was widely developed these last years. N.J. Mauser was one of contributors, as well as on the notion of Wigner measure which is the key of the analysis developed by Z. Ammari and F. Nier. Generally, the mean field asymptotic is admitted is a good approximation of the N-body problem when N exceed about ten. It concerns the asymptotics of the reduced density matrices for one particle which does not describe the dynamics of the correlations. An objective is to test the validity of the mean field dynamics for reduced density matrices for 2 particles. For numerical tests, the discrete models which were not really handled in detail in the previous works of Z. Ammari and F. Nier seem adapted well. The thesis will thus include several steps: adapt the previous results from Z. Ammari and F. Nier to discrete models , develop numerical methods, for simple but relevant systems, allowing to validate the approximation of mean field and the formulas for the dynamics of the correlations. About numerics, symplectic numerical scheme are used, developed specifically these last years for the discretization of the hamiltonian equations. A last possible step concerns the combination of both asymptotics, that is mean field and approximation of the continuous models by the discrete models.

Orientador: José Augusto Chinellato / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Física Gleb Wataghin / Made available in DSpace on 2018-08-29T05:01:52Z (GMT). No. of bitstreams: 1 MedinaJaime_Miguel_D.pdf: 6686309 bytes, checksum: 48654e10cf1138cdc89eb810557a427d (MD5) Previous issue date: 2015 / Resumo: A produção exclusiva de bósons Z é um processo difrativo, teoricamente representado pela troca de um objeto com os números quânticos do vácuo (pomeron- IP), o qual pode ser tratado no modelo padrão no enfoque do mecanismo de dipolo, via fotoprodução. A caraterística principal deste tipo de processo é que os dois prótons emergem intactos após a colisão com momentum transverso pequeno. Assim, os prótons são espalhados muito frontais e escapam à detecção., restandonos como criterio de e. Espera-se , onde um próton irradia um fóton virtual, o qual flutua para um par quark anti-quark os quais são espalhados elasticamente pela troca de dois glúons emergentes do outro próton, e se materializa num bóson Z. Além disso, os dois prótons emergem intactos após a colisão com momentum transverso pequeno, assim prótons são espalhados muito frontais e escapam à detecção. Portanto, o critério usado para a identificação de eventos exclusivos de bósons Z decaindo em par múons é o número de traços adicionais no vértice, mas ainda resta a possibilidade de haver uma dissociação de pelo menos um dos prótons. Neste caso, a medida da seção de choque respectiva será contaminada. São expostos três diferentes métodos para a pré-seleção des eventos contendo eventos exclusivos. A estratégia de análise proposta para selecionar eventos exclusivos é baseada no decaimento de bósons Z em pares ???? caraterizados por grande momento transverso, para o qual exploramos múons em uma região cinemática de momento transverso Pt(?)>20 GeV, massa invariante M(????)>40 GeV/c² e pseudo-rapidez |?|<2,5. Adicionalmente a estes cortes, exigimos "zero traços" extras no vértice e, por último que o par de múons sejam back-to-back com balanço no Pt. Nesta Tese se apresenta um estudo da produção exclusiva de bósons Z em colisões próton-próton para energias de centro de massa igual a ?s=7 TeV no experimento CMS/LHC. Esta análise foi feita usando simulações para processos de Drell-Yan, fotoprodução de múons e dados coletados pelo detector CMS de colisões próton-próton com ?s=7 TeV durante o ano de 2011, correspondendo a uma luminosidade integrada de 5,09 fb?¹. Nenhum excesso significante de sinal foi extraído nas produções exclusivas de fazemos uma estimativa de eventos esperados nas produções exclusiva e bósons. Nenhum candidato a bóson Z exclusivo foi possível de observar, isto devido ao fato da baixa estatística e o enorme background proveniente de processos de Drell-Yan., que mesmo sendo processos não exclusivos contaminarem nossa amostra de dados devido ao fato de que os prótons escapam de nossa detecção e o único critério de exclusividade é o de o número de traços extras no vertice do evento seja igual a zero, mas devido a que os prótons podem dissociar sim ser detetados e nós foi impossível dete devido a que assim prótons são espalhados muito frontais e escapam à detecção. Entretanto, a seção de choque para processos de produção exclusiva de bósons Z é encontrada a ser ?excl(Z?????)<13,3 fb para um nível de confiança de 95%. Este é o primeiro resultado preliminar para este tipo de processo na escala de energia de 7 TeV, onde cabe destacar que este limite foi melhorado com respeito a resultados publicados pela colaboração CDF para ?s = 1,9 TeV / Abstract: he exclusive Z boson production is a diffractive process theoretically represented by the exchange of an object with the quantum numbers of vacuum (pomeron-IP), which is predicted by the Standard Model in the dipole mechanism approach, via photoproduction. The main feature of this type of process is two forward outgoing protons intact after the collision with small transverse momentum, the protons are scattering very front and escape detection. Then, the approach taken to detect exclusive Z bosons events decaying in to muon pair is the number of additional tracks on the vertex, but there is still the possibility of dissociation of at least one proton, then the measurement of cross section will be contaminated. It's exposed three different methods for the pre-selection events containing exclusive Z bosons. The strategy proposed to exclusive selection events, is based on the decay of Z bosons on pairs ???? featured by large transverse momentum, for which we explored muons in a kinematic region with transverse momentum Pt(?)>20 GeV, Invariant mass M(????)>40 GeV/c² and pseudorapidity |?|<2,5. The additional cuts, require zero extra tracks on vertex and finally the pair of muons are back-to-back with momentum transverse conservation . This thesis presents a search for exclusive Z boson production in proton proton collisions at ?s=7 TeV center of mass energy in the experiment CMS/LHC. This analysis was made using simulations to Drell-Yan processes, photoproduction of muon and data collected by the CMS detector on proton proton collisions with ?s=7 TeV in 2011, for 5.09 fb?¹ integrated luminosity record. No exclusive Z????? candidates are observed, because low statistical and huge background contribution from Drell-Yan processes. But even so, the cross section for the exclusive Z bosons production is found to be ?excl(Z?????)<13.3 fb at 95% C.L. This is the first very preliminary results for 7 TeV, where we highlight that it limit has been improved respect to the results published by the CDF collaboration to ?s = 1.9 TeV / Doutorado / Física / Doutor em Ciências / 147301/2011-04 / CNPQ

In dieser Arbeit wird die Suche nach geladenen Higgs Bosonen (H±) vorgestellt. Dafür wurden Proton–Proton Kollisionen, die bei einer Schwerpunktsenergie von 13 TeV in den Jahren 2015 und 2016 mit einer integrierten Luminosität von 36.1 fb−1 mit dem ATLAS-Experiment produziert wurden, untersucht. Die Existenz solcher geladener Higgs Bosonen wird in verschiedenen Modellen jenseits des Standardmodells vorhergesagt und ist auch dadurch motiviert, das dass Standardmodell nicht immer eine Erklärung für verschiedenste beobachtete Phänomene liefern kann. Diese Arbeit konzentriert sich auf geladene Higgs Bosonen, die eine höhere Masse als das top Quark besitzen und über H± → tb zerfallen. Die H± Produktion, in Verbindung mit einem top und einem bottom Quark pp → tbH±, wird im Massenbereich von 200 bis 2000 GeV untersucht. Die Suche nach H± in dieser Arbeit beschränkt sich auf Endzustände mit einem geladenen Lepton und mehreren Jets. Mit Hilfe eines boosted decision trees werden verschiedenste kinematische Variablen miteinander kombiniert, um dadurch das H± Signal besser von dem Standardmodell Untergrund unterscheiden zu können. Es wurde kein signifikanter Unterschied zum vorhergesagten Standardmodell-Untergrund gemessen und deshalb Ausschlussgrenzen für den Produktionswirkungsquerschnitt mal Verzweigungsverhältnis dieses H± Zerfalls berechnet. Weitere Ausschlussgrenzen wurden für den tanβ Parameter des MSSM Modells für die mhmod− und hMSSM Benchmark-Szenarien bestimmt. Die Ergebnisse dieser Arbeit übertreffen alle bisherigen Ausschlussgrenzen - insbesondere werden zum ersten Mal Erkenntnisse über den Massenbereich bis zu 2000 GeV gewonnen. / This thesis presents a search for charged Higgs bosons produced in proton–proton collisions at a centre-of-mass energy of 13 TeV, using 36.1 fb−1 of data collected by the ATLAS detector at the LHC in 2015 and 2016. The existence of charged Higgs bosons is predicted by various theories Beyond the Standard Model and it is motivated by the inadequacy of the Standard Model to explain some observed experimental phenomena. The work focuses on charged Higgs bosons heavier than the top quark and decaying via H± → tb. The production in association with a top and a bottom quark (pp → tbH±) is investigated in the mass range between 200 and 2000 GeV. A final state containing one charged lepton and jets is considered. Multiple kinematic variables are combined using a boosted decision tree (BDT) in order to separate signal and background. The output of the BDT is used to perform a profile likelihood fit of the Monte Carlo predictions to the observed data. No significant excess of events above the expected Standard Model background is observed, therefore upper limits are set for the cross-section of the charged Higgs boson production times the branching fraction of its decay. Limits are also provided for the tanβ parameter of the MSSM, in the mhmod− and hMSSM benchmark scenarios. The work improves the reach of all previous searches, including for the first time masses ranging up to 2000 GeV.