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The generation of vector boson mass via the Higgs mechanism in the Standard Model has been confirmed by the 2012 discovery of a candidate Higgs boson in the H&rarr;WW, H&rarr;ZZ, and H&rarr;&gamma;&gamma; decay channels. In contrast, the Yukawa couplings hypothesized to provide the mass of fermions in the Standard Model have yet to be observed. The H&rarr;&tau;&tau; decay channel currently provides the best opportunity for observing these couplings. This thesis describes two separate but related searches for Higgs boson decays in the H→&tau;&tau; decay channel using proton-proton collisions recorded by the ATLAS detector. The first analysis is a general search for all Higgs boson production mechanisms leading to a H&rarr;&tau;&tau; decay using 4.5 fb⁻¹ of 7 TeV and 20.3 fb⁻¹ of 8 TeV proton-proton collision data. A deviation from the background-only hypothesis is observed with a significance of 4.5&sigma; for a hypothetical Higgs boson mass of m_H = 125 GeV — a strong indication of a H&rarr;&tau;&tau; signal. For the same mass point, the best fit value for the signal strength is found to be 1.43 ^&plus;0.43<sub style='position: relative; left: -2.4em;'>−0.37</sub> x the Standard Model expectation. The second analysis is a search for Higgs boson production in association with a vector boson using 20.3 fb⁻¹ of 8 TeV proton-proton collision data. Results in the Z_llH&rarr;_&tau;l&tau;h channel indicate limits of 9.14 x the Standard Model expectation for VH signal production at m_H = 125 GeV. In addition, two studies on enhancement of computing performance in the ATLAS trigger and data analysis pipeline are presented.

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Thèse numérisée par la Division de la gestion de documents et des archives de l'Université de Montréal.

Thèse numérisée par la Division de la gestion de documents et des archives de l'Université de Montréal

Submitted by Valquíria Barbieri (kikibarbi@hotmail.com) on 2017-05-26T21:59:31Z No. of bitstreams: 1 DISS_2014_William Kennedy do Amaral Souza.pdf: 2007327 bytes, checksum: 43d66663b123a5ee177b7c2237b846d5 (MD5) / Approved for entry into archive by Jordan (jordanbiblio@gmail.com) on 2017-05-29T16:24:34Z (GMT) No. of bitstreams: 1 DISS_2014_William Kennedy do Amaral Souza.pdf: 2007327 bytes, checksum: 43d66663b123a5ee177b7c2237b846d5 (MD5) / Made available in DSpace on 2017-05-29T16:24:34Z (GMT). No. of bitstreams: 1 DISS_2014_William Kennedy do Amaral Souza.pdf: 2007327 bytes, checksum: 43d66663b123a5ee177b7c2237b846d5 (MD5) Previous issue date: 2014-04-03 / O trabalho, ao longo da História, passa por transformações deixando o seu intuito central de humanizar os indivíduos e passa a desfigurá-los, causando um estranhamento frente ao produto final obtido no processo de produção. Na contemporaneidade, esse estranhamento é naturalizado pelo discurso globalizante neoliberal e pela manipulação empreendida pelas novas formas de estruturação do trabalho. Lutando contra esssa naturalização e com um cenário de precarização estrutural do trabalho, marcado pelo crescente desemprego e exclusão social, trabalhadores(as) pertencentes às camadas populares buscam a produção da vida por intermédio de processos coletivos em que se destaca a Produção Associada. O presente estudo, ocupa-se da reflexão sobre a forma como alguns trabalhadores(as) do Assentamento 14 de Agosto, em Campo Verde, Estado de Mato Grosso, que é fruto da luta do Movimento dos Trabalhadores Rurais Sem-Terra (MST), uniram-se em torno da Cooperativa de Produção Agropecuária Canudos, dita COOPAC, para produzirem a vida material e imaterial de forma associada sem as constantes ambições da produção capitalista. Para o desenvolvimento da pesquisa, utilizamo-nos do materialismo histórico, sobretudo das categorias “Trabalho”, “Experiência” e “Produção Associada”. Valemo-nos principalmente, das reflexões emprendidas por Marx, Thompson e Tiriba para entender que, ao realizarem seu trabalho, os trabalhadores(as) da COOPAC não só aprendem a produzir mercadorias, mas também saberes, educação, conhecimento, relações sociais e consciência política. Optamos em realizar um estudo de caso, em que os dados foram coletados por meio da observação direta das práticas cotidianas dos trabalhadores(as) envolvidos. Foram feitas entrevistas (semiestruturadas) individuais gravadas, procurando destacar questões relacionadas às histórias de vida dos trabalhadores(as) do Assentamento 14 de Agosto. A análise mostrou que a Produção Associada, por meio de uma pedagogia própria, é uma estratégia do MST para que os trabalhadores(as) vivenciem dignamente a luta na terra, conquistem a partir do seu exemplo novos integrantes para esta luta e contestem as relações de trabalho subordinadas ao capital. Mas a análise mostra também que há enormes dificuldades para o MST quando da implementação desse projeto devido às contradições entre acampamento/assentamento e entre coletivo/individual. Mesmo assim, a Produção Associada é um instrumento político-pedagógico, já que se configura como uma estratégia de produção que questiona a lógica capitalista, apesar de estar inserida nesse contexto. / The work throughout history undergoes transformations leaving its central purpose of humanizing individuals and proceeds to disfigure them, causing an strangeness front of the final product in the production process. In contemporary times, this strangeness is naturalized by the globalizing neoliberal speech and the manipulation undertaken by new ways of work structuring. Fighting against this naturalization and with a backdrop of structural precariousness of work, marked by rising unemployment and social exclusion, workers belonging to the lower classes seek the production of life through collective processes which highlights the Associated Production. This text deals with the reflection on how some workers of August 14th Settlement in Campo Verde, state of Mato Grosso, which is the fruit of the struggle of the Movement of Workers Country Without Land (MST), coalesced around of co-op of production agriculture Canudos - COOPAC - to produce the material and immaterial life so without the constant associated ambitions of capitalist production. For the development of research in the use of historical materialism, particularly the categories "Work", "Experience" and "Associated Production”. We use mainly the reflections undertaken Marx , Thompson and Tiriba to understand that to do their jobs, the workers the COOPAC not only learn to produce goods, but also knowledge, education, knowledge, social and political consciousness. We chose to conduct a case‟s study, in which data were collected through direct observation of daily practices of workers involved. We are relying on further interviews (semi-structured) recorded individual, seeking to highlight issues related to the life stories of workers nesting August 14th. The analysis showed that the Associated Production, through its own pedagogy, is a strategy of the MST for workers experience the fight worthily on land, and through this example conquer new members for this fight and contest the subordinate working relationships capital. But the analysis also shows that there are enormous difficulties in implementing MST for this project due to the contradictions between camp/settlement and between collective/individual. Even so, the Associated Production is a political-pedagogical instrument, since it sets up as a production strategy that questions the logic of capitalism, despite being included in it.

Une recherche du boson de Higgs du Modèle Standard produit en association avec un boson W ou Z et se désintégrant en une paire quark-antiquark b a été effectuée avec le détecteur ATLAS. Les données de collisions proton-proton utilisées ont été accumulées durant le Run 2 du Grand Collisionneur de Hadrons du CERN à une énergie dans le centre de masse de 13 TeV, et correspondent à une luminosité intégrée de 79.8 fb⁻¹. Trois canaux contenant zéro, un ou deux leptons chargés (électrons ou muons) sont considérés, correspondant à chacune des désintégrations leptoniques d'un boson W ou Z: Z->vv, W->lv et Z->ll. Pour un boson de Higgs de masse 125 GeV, un excès d'événements par rapport aux bruits de fonds des autres processus du Modèle Standard est observé avec un niveau de signification statistique de 4.9 déviations standard, à comparer à 4.3 attendues. Le rapport du nombre d'événements observé au nombre attendu est mesuré être 1.16 +0.27/-0.25 = 1.16 +/-0.16(stat) +0.21/-0.19(syst). Ce résultat est combiné avec d'autres d'ATLAS sur la recherche du boson de Higgs se désintégrant dans le mode bbbar, utilisant des données du Run 1 et du Run 2. Le niveau de signification mesuré (attendu) pour ce mode de désintégraion est de 5.4 (5.5) déviations standard, ce qui en constitue la première observation directe. De plus, une combinaison des résultats du Run 2 sur la recherche de la production associée du boson de Higgs et d'un boson W ou Z conduit à un niveau de signification observé (attendu) de 5.3 (4.8) déviations standard, et donc à la première observation de ce mode de production. / A search for the Standard Model Higgs boson produced in association with a W or Z boson, and decaying to a bb pair has been performed with ATLAS detector. The data were collected in proton-proton collisions during Run 2 of the Large Hadron Collider at a centre-of-mass energy of 13 TeV, and correspond to an integrated luminosity of 79.8 fb⁻¹. Three channels containing zero, one and two charged leptons (electrons or muons) have been considered to target each of the leptonic decays of the W or Z boson, Z->vv, W->lv et Z->ll, referred to as as the 0-lepton, 1-lepton and 2-lepton channels, respectively. For a Higgs boson mass of 125 GeV, an excess of events over the expected background from other Standard Model processes is found with an observed significance of 4.9 standard deviations, compared to an expectation of 4.3 standard deviations. The ratio of the measured signal events to the Standard Model expectation equal 1.16 +0.27/-0.25 = 1.16 +/-0.16(stat) +0.21/-0.19(syst). The result is also combined with the other results from the searches for the Higgs boson in the bb 18 decay mode in Run 1 and Run 2, the combination yields an observed (expected) significance of 5.4 (5.5) 20 standard deviations, and therefore provides a direct observation of the Higgs boson decay into a bb pair. In addition, a combination of Run 2 results searching for the Higgs boson produced in association with a W or Z boson yields an observed (expected) significance of 5.3 (4.8) standard deviations, and therefore provides a direct observation of Higgs boson being produced in association with a W or Z boson.