This thesis presents searches for evidence for Weakly Interacting Massive Particles (WIMPs) and Extra Dimensions in proton-proton collisions recorded by the ATLAS experiment at the CERN Large Hadron Collider (LHC). The WIMP is one of the main candidates to constitute the particle content of Dark Matter. Extra Dimensions are introduced in several theories in order to explain the apparent weakness of gravity when compared to the other interactions in Nature. Theories with WIMPs as well as Extra Dimensions can manifest themselves at the LHC, with experimental signatures characterized by an energetic hadronic jet associated with large missing momentum. These signatures are known as monojet signatures, and are investigated in this thesis.  The first analysis is performed using L = 20.3 fb-1 of proton-proton collisions at √s = 8 TeV recorded in the ATLAS Run 1. The second analysis is performed using L = 3.2 fb-1 of proton-proton collisions at √s = 13 TeV recorded in the ATLAS Run 2. No significant excess over the expected background is found in either of the analyses. New exclusion limits are set at 95% confidence level on Dark Matter particle production. New limits are also set on graviton production in the so-called ADD scenario with Extra Dimensions.

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La dynamique des cratons reste, encore actuellement, énigmatique dans la mesure où ceux-ci sont souvent considérés comme des domaines stables à l’échelle des temps géologiques. Dans ce travail, nous avons reconstitué l’évolution d’un des plus grands cratons, le Craton Ouest Africain. Nous nous sommes également penchés sur l’étude de ses bordures nord et ouest (Anti-Atlas et marge atlantique respectivement). Cette étude utilise les méthodes de thermochronologie basse-température (traces de fission et (U-Th-Sm)/He sur apatite) ainsi que la géologie structurale. Le choix de ce craton est justifié par les multiples contextes géologiques dont témoignent ses bordures au cours du Phanérozoïque (plateforme, avant-pays distal, marge passive). Ces contextes variés au cours du temps en font donc une cible idéale pour évaluer l’influence des diverses forces susceptibles d’affecter le craton.Tout d’abord, suite à une subsidence importante au cours du Paléozoïque, le craton enregistre un refroidissement important entre le Jurassique supérieur et le Crétacé inférieur, postérieurement à l’ouverture de l’Atlantique Central. Cet événement n’est pas directement lié aux seuls processus affectant les marges passives puisque non seulement la marge est affectée, mais aussi l’intérieur du craton (jusque 800 km à l’intérieur des terres) et le domaine mobile non-cratonique au Nord. Ce refroidissement traduit une phase d’exhumation kilométrique qui permet alors le dépôt d’une épaisse séquence détritique sur la plateforme saharienne. L’hypothèse d’un raccourcissement comme explication n’est pas valide et l’hypothèse d’une anomalie thermique mantellique à cette époque rend mieux compte de cet événement d’érosion majeur. L’hypothèse thermique possède un autre avantage : celui de rendre compte du réchauffement qui suivit à l’Apto-Albien et au début du Crétacé supérieur, à la fois par le craton mais aussi par ses bordures, par le biais de la subsidence thermique.Deuxièmement, à partir du Crétacé supérieur, la tendance générale est au refroidissement dans toute la région étudiée, synchrone avec l’initiation de la convergence Afrique/Europe. La chaîne du Haut Atlas au Maroc représente à ce moment un témoin privilégié des déformations se produisant pendant le Cénozoïque. Nous avons déterminé un calendrier tectonique précis dans l’avant-pays méridional de la chaîne, afin d’avoir un point de comparaison avec l’enregistrement cratonique. Ainsi, une première phase tectonique se déroule à l’Eocène supérieur. Celle-ci fait écho à un événement de déformation de plus grande échelle qui affecte toute le craton, résultant sans doute d’une réorganisation de grande ampleur dans la dynamique de la convergence. La phase récente Plio-Quaternaire est bien décrite à l’échelle de l’Afrique du Nord dans la chaîne Atlasique, mais pourrait s’avérer trop récente pour pouvoir être décelée par nos thermochronomètres à l’intérieur du domaine cratonique. Enfin, une phase de soulèvement spécifique au domaine atlasique marocain est enregistrée pendant le Miocène inférieur-moyen et met en place des nappes dans la chaîne. Les thermochronomètres basse-température ne la détectent pas à l’intérieur du craton, et elle pourrait donc être géographiquement restreinte au domaine atlasique.Ce travail a démontré que l’absence de sédiments au cours du Méso-Cénozoïque, qui en première approche font de ce craton une zone dite « stable », occulte une réalité géologique autre, faite de la succession de plusieurs phases épeirogéniques. Une évaluation des processus à l’œuvre permet de proposer que les phénomènes mantelliques ainsi que les transferts de contraintes sont des acteurs majeurs à l’origine de ces mouvements. Néanmoins, la juste contribution de chacun de ces processus nécessite encore un travail approfondi. / The dynamic evolution of cratonic domains remains enigmatic as they are usually considered as stable through geological times. In this work, we unraveled the evolution of one of the largest cratonic area, the West African Craton (WAC), and its north and west boundaries (Anti-Atlas and Atlantic passive margin, respectively), through low-temperature thermochronology (apatite fission-track and (U-Th)/He thermochronology) and structural geology. The WAC was studied since its boundaries witnessed many different geological settings (platform, distal foreland, passive margin) during the Phanerozoic, making it a good candidate to evaluate the various driving forces acting on the craton.First, after a continuous Paleozoic subsidence, the craton records the most important cooling event between Late Jurassic and Early Cretaceous, postdating the onset of the Central Atlantic Ocean spreading. This event is unrelated to the sole passive margin in itself and affected both the craton (up to 800 km inland) and the mobile boundary in the north (Anti-Atlas and High Atlas). It represents kilometer-scale erosion that led to the deposition of thick detrital formations, the red beds, across the whole Saharan platform. This event is not characterized by shortening and is better explained through a mantle-related thermal anomaly during this exhumation. The thermal hypothesis explains the subsequent thermal subsidence undergone by the craton and its north boundary during the Aptian-Albian and the early stages of the Late Cretaceous.Second, from Late Cretaceous onward, dominant cooling trend has imprinted the thermal histories of the studied region, coevally with the onset of the Africa/Europe convergence.The High Atlas belt in Morocco is an accurate witness of the deformations occurring during Cenozoic times. We determined the precise tectonic schedule in the southern foreland of the belt and compared this evolution with the cratonic one. We show that the first Eocene tectonic event echoes to a major craton-scale deformation and results probably from a significant geodynamic change in the convergence zone. The Pliocene-Quaternary phase, well known at the North African scale, is only recorded in the Atlas belt, but might be too recent to have significantly imprinted the thermochronological record inside the craton. Finally, another uplift specific to the Moroccan Atlas Belt during Early to Middle Miocene led to the emplacement of tectonic nappes. This event is not recorded by LTT on the craton and may be restricted to its mobile boundary.This work demonstrates that, despite the lack of Mesozoic-Cenozoic sediment record that may advocate for a stable geological history, the West African Craton suffered significant epeirogenies during this period. Deep seated processes as well as stress transmission prove to be good candidates to account for these cratonic motions, although further work is needed to unravel the exact contribution of these various processes.

Thesis (MTech (Horticulture))--Cape Peninsula University of Technology, 2016. / This study focused on optimising four types of in-vitro conservation methods, namely: 1), micropropagation, 2) in-vitro slow growth, 3) seed germination and 4) cryopreservation for selected endangered plant species indigenous to the Cape Floristic Region. It is one of the targets set by United Nations millennium development goals, to integrate different conservation measures in order to preserve plant diversity and mitigate losses of genetic diversity. Therefore this study uses Phalaenopsis hybrids as a trial species that can be studied for the conservation of endangered Disa and Eulophia species through micropropagation and in vitro slow growth. Also conservation attempts on Leucadendron and Mimetes species that occur in the Cape Floristic Region were attemted to increase population densities by increasing germination percentages using smoke. Furthermore, the study attempted to store seeds by assessing different cooling rates for optimising cryopreservation measures for effective conservation. The use of tissue culture to increase propagules especially critically endangered species in South African has proven to be feasible. For the trial hybrids, shoot and protocorm explants of Phalaenopsis Psychosis Pink X P. No. 1; P. Large white X P. Large pink; P. No. 1 X P. Large pink; P. Mini pink X Brighton belle; and the P. aphrodite formed clusters of protocorms and shoots when cultured on ½ strength MS media supplemented with 10, 20 and 30gL-1 banana extract or ½ strength Murashige and Skoog, (1962) (MS) media supplemented with peptone. Continuous protocorms formation could therefore be obtained by culturing endangered Disa and Eulophia shoots and protocorms on banana containing media. Plantlet conversion from somatic embryos produced on 10gL-1 banana extract enriched media was successfully achieved on ½ strength MS supplemented with 20gL-1 sucrose and no plant growth regulators in the medium. However, optimum rooting was achieved on ½ strength MS supplemented with 30gL-1 of banana extract and this medium yielded the highest survival percentages for plantlet acclimatisation. Furthermore, ½ strength MS supplemented with 1gL-1 of peptone served as a stimulant for shoot development and protocorm formation. When coupled with banana extract at all stages of development, regeneration and rooting were enhanced.

Esta tese teve como objetivo identificar a norma semântico-lexical de cinco municípios da Região Norte do Alto Tietê- ReNAT, no estado de São Paulo,e pauta-se pelos estudos dialetológicos, geolinguísticos e sociogeolinguísticos. O local da pesquisa, a antiga Vila de Nossa Senhora da Conceição dos Guarulhos, é atualmente uma região composta por cinco municípios: Guarulhos, Arujá, Santa Isabel, Mairiporã e Nazaré Paulista. Está situada na Região Metropolitana de São Paulo, com exceção do quinto município, Nazaré Paulista, localizado na microrregião de Atibaia. A origem da região composta pelos cinco municípios, corpus do trabalho, remonta à época da fundação de São Paulo. Três municípios estão situados na região do Alto Tietê, ao norte do rio que leva o mesmo nome, por isso é denominada ReNAT. A vila era inicialmente povoada pelos índios Maromomis. A tese fundamentou-se nos trabalhos linguísticos voltados para a Dialetologia, a Geolinguística a Sociolinguística variacionista, a Sociolinguística interacional, a Semântica e a Lexicologia. Além do tratamento quantitativo dos dados, conforme a proposta de Muller, privilegiou a abordagem dos aspectos semânticos-lexicais a partir de Pottier e Rastier, e baseou-se na concepção de norma de Coseriu. Assim, de acordo com os procedimentos teórico-metodológicos atuais da Geolinguística e da Sociogeolinguística, aplicaram-se as 202 questões do questionário Semântico-Lexical (QSL) do projeto ALiB e, também, 31 questões do Questionário Semântico-Lexical do Projeto Estudo sociogeolinguístico do Município de São Paulo, elaborado pelo Grupo de Pesquisa em Dialetologia e Geolinguística (GPDG) da Universidade de São Paulo. As entrevistas foram desenvolvidas in loco, ou seja, nos seis pontos da pesquisa, localizados nos cinco municípios. As 233 questões, dos dois questionários, foram aplicadas a 24 sujeitos-entrevistados de ambos os gêneros masculino e feminino em duas faixas etárias, quais sejam: 18 a 30 anos e 50 a 65 anos. Os resultados estão apresentados em gráficos ou tabelas com informações de frequências absoluta e relativa. A esses dados, seguiu-se a análise interpretativa dos resultados de cada questão. As respostas dos sujeitos-entrevistados, bem como a localização destes estão registradas em 233 cartogramas linguísticos. Acredita-se que as palavras refletem a história dos sujeitos, confirmando que para a expressão linguística são exigidos fatores internos e estes estão associados a fatores externos à linguagem. Assim, a língua, conforme o espaço, variação diatópica, sofre variações. Toda a dinamicidade da língua é evidenciada sobretudo no léxico, nível linguístico que melhor expressa a mobilidade das estruturas sociais, o qual reflete a maneira como a sociedade vê e representa o mundo. Ao final da pesquisa, mostrou-se o quadro da diversidade linguística na região, constatando-se a variação semântico-lexical na ReNAT. Enfim, a tese registrou a realidade linguística dos cinco municípios que compõem a região pesquisada, com relação ao léxico utilizado pelos sujeitos-entrevistados. Sabe-se que a área pesquisada tem dimensões pequenas, mas, ainda assim, revela sua importância para os estudos sociogeolinguísticos, pois expressa a situação real de uso da linguagem do sujeito num espaço e momento determinado, e também denota as características sócio-histórico-culturais de uma comunidade linguística. / This thesis aims to identify the semantic and lexical norm of five counties of the North region of the High Tietê- ReNAT, in the state of São Paulo, and it is based on the dialectological, geolinguistic and sociogeolinguistic studies. The premise of the research, which is the ancient Vila de Nossa Senhora da Conceição dos Guarulhos, is currently composed of five counties: Guarulhos, Arujá, Santa Isabel, Mairiporã and Nazaré Paulista. It is located in the Great São Paulo area, except for Nazaré Paulista, that is situated in the micro region of Atibaia. The origin of the region composed of five counties, the corpus of this research goes back to the epoch of the foundation of São Paulo. Three counties are situated in the region of High Tietê, to the north of the river which takes the same name, that is why it is called ReNAT. This thesis has its fundamentals on the linguistic works featured by the dialectological and sociogeolinguistic studies focusing on the semantic and lexical aspect. The theory has been based on linguistic studies which have helped develop essays on Dialectology, Geolinguistic; Variational, Sociolinguistc; Interactional Sociolinguistic, Semantics and Lexicology. Besides the quantitative treatment of data, as of the studies of Muller, we have prioritized the approach of the lexical and semantic aspects, based on Pottier and Rastier, stemming from the conception of norm by the theory of Coseriu. Based on the recent methodological procedures of Geolinguistic and Sociogeolinguistic, 202 questions of the Semantic-Lexical (QSL) questionnaire of the ALIB project have been applied as well as the 31 questions of the questionnaire lexical-semantic of the Atlas of the São Paulo city (ALESP), created by the Grupo de Pesquisa em Dialetologia e Geolinguistica(GPDG) of the University of São Paulo. The interviews have been carried out in loco, that is, on the 6 places of research where the five counties belong to. The 233 questions of the 2 questionnaires were applied to 24 subjects of both genre- male and female- in two age brackets: from 18 to 30 and 50 to 65 years old. The results are presented in tables, graphs with information of absolute and relative frequency. To this data, followed the interpretative analysis of the results of each question. The answers of the interviewee- subjects are registered in 233 linguistic cartograms. It is believed that the words reflect the story of the individuals, confirming that to the linguistic expression are demanded the internal factors which are associated to the external factors of the language. Thus, language according to space, suffers variation and all this dynamism is evidenced on the lexicon- the linguistic level that better expresses the mobility of the social structures, which reflects the way the society sees and represents the world. A the end of this research, we have shown the picture of linguistic diversity of the aimed region by proving the variation of the ReNAT. At last, this research has registered the linguistic reality of the five counties that compose the region as to the lexicon used by the subjects interviewed. The studied area has small dimensions, but, even so, it reveals great importance to socio-geo-linguistic studies , for, they express the real usage of language in a certain space and time as well as the socio-historical and cultural features of a linguistic community.

A search for Beyond the Standard Model physics is performed with the ATLAS detector in the opposite sign dimuon channel using the 20 fb 1 of data collected in 2012 at √s = 8 TeV. No excess is found above the Standard Model expectation. Using a Bayesian statistical analysis, model dependent 95% Credibility Level Bayesian exclusion limits are extracted for two models of gravitationally-related beyond the Standard Model phenomena. For the ADD and RS quantum black hole models, limits of 3.32 and 1.95 TeV are set on the extradimensional Planck Scale, and for ADD Large Extra dimensions, limits ranging from 2.8-4.4 TeV are set on the string scale for the GRW, HLZ and Hewett formalisms. In addition, a study is performed to estimate the effect of increasing noise cuts in the ATLAS Level-1 Calorimeter Trigger on the physics efficiency of W ! e and t¯t and on the Level-1 missing transverse energy trigger rate. Results suggest that higher noise cuts could reduce the Level-1 missing transverse energy trigger rate with a minimal loss of physics efficiency.

This thesis presents the measurement of the production cross section of a W boson with a single charm quark in 7 TeV proton-proton collisions using the ATLAS detector at the Large Hadron Collider. The data analysed correspond to an integrated luminosity of 4.6 fb 1 and were collected during 2011. This is the first time that ATLAS data has been used for this particular measurement. This cross section is of particular interest as a probe of the strange quark density of the proton. Typically, the strange quark density is considered to be suppressed relative to that of the other light-quarks in the proton sea. However, some analyses suggest a more symmetric composition of light-quarks in the proton sea. The results of this study aim to improve the precision of the determination of the strange quark density. The analysis uses events where the W boson decays to a muon and a neutrino. In such events, the charm quark is identified by its semileptonic decay to a soft muon within a hadronic jet. The charge correlation between the W boson and the soft muon is exploited to reduce the backgrounds substantially. The analysis results are combined with those obtained using additional decay channels. The measured cross section provides further constraint for the determination of the strange quark density, advancing the knowledge of the fundamental structure of the proton. The results are compared with predictions of next-to-leading-order QCD calculations obtained using various parton distribution function parameterisations. Additionally, the ratio of the strange-to-down sea-quark distributions is determined to be 0.96+0.26 0.30 at Q2 = 1.9 GeV2. This supports the hypothesis of a symmetric composition of light-quarks in the proton sea. The cross section ratio (W+ + c)= (W + c) is also determined and compared with different predictions for the asymmetry of the strange and anti-strange quark distribution functions.

A measurement of the Drell-Yan differential cross section at low invariant mass is presented in the di-muon channel. A 1.64 pb−1 dataset of √s = 7 TeV proton-proton collision data collected by the ATLAS experiment at the LHC is used. The measurement is made in an invariant mass range of 26 < M < 66 GeV where M is the invariant mass of the muon pair. A review of the relevant theoretical physics and the ATLAS detector is made. The analysis is described with particular attention paid to the determination of the isolation efficiency corrections for the Monte Carlo and the estimate of the multijet background. The fiducial differential cross section is calculated with a statistical uncertainty that varies between 0.8% and 1.2%. The systematic uncertainty is seen to vary between 2.4% and 4.1%. A cross section extrapolated to the full phase space is also presented. This is dominated by theoretical uncertainties from the variation of the factorisation and renormalisation scales. The obtained fiducial differential mass cross section is compared to theoretical predictions at NLO and NNLO in perturbative QCD. It is shown that a move beyond NLO is needed to describe the distribution well due to the restrictions of using a fixed order theoretical prediction. A combination with the electron channel measurement is also briefly discussed as well as comparisons to a di-muon measurement in an extended invariant mass range. This allows similar, but stronger conclusions to be drawn. A discussion is made of a PDF fit that uses the measurement presented here. The fit demonstrates the impact of the measurement on the PDFs and further supports the conclusion that a move to NNLO in pQCD is needed to describe the data.

This thesis presents studies of the single top t-channel in the electron plus jets mode. In order to understand this channel, an account of the present theoretical models is given. This work relies on collisions data from the ATLAS detector and its components are presented here. A summary of the work involving the SCT, part of the tracking system in ATLAS, is also explained here. Studies were performed to optimize the measurement of the Lorentz Angle of the holes in the Silicon for the initial data taking period. The data studied was acquired by ATLAS during 2011, with a total integrated luminosity of 4.7 pb−1 at a √s = 7 TeV. Monte Carlo simulation of signal and background events was also used throughout. Background studies were performed to correctly determine the expected amount of QCD via the Jet Electron data-driven method and of light or heavy flavour jets produced in association with a W boson, which is one of the dominant backgrounds for the t-channel. A cut based analysis was then applied to the data and simulation in order to better discriminate the t-channel signal. A binned likelihood fit to the invariant mass of the reconstructed top quark was performed and the cross section value for the t-channel process was calculated: σt−channel = 62.2±8.0(stat)+8.6 −8.8(syst) pb which is in good agreement with the theoretically predicted value. Finally, the response (preco T /ptrue T ) of light quark or gluon initiated jets is evaluated for both the t-channel and the Wt associated production, in order to determine the flavour composition uncertainty, as part of the framework that provides the jet energy scale uncertainties in a multiple jets environment. Other sources of system- atics are also reviewed.

In 2012 a resonance with a mass of 125 GeV resembling the elusive Higgs boson was discovered simultaneously by the ATLAS and CMS experiments using data collected from the Large Hadron Collider (LHC) at CERN. Its observation finally confirms the mechanism for Spontaneous Electroweak Symmetry Breaking (EWSB) necessary for describing the mass structure of the electroweak (EW) gauge bosons. In 2013, Peter Higgs and Francois Englert were awarded the Nobel Prize in physics for their work in developing this theory of EWSB now referred to as the Higgs mechanism. The explanation for EWSB is often referred to as the last piece of the puzzle required to build a consistent theory of particle physics known as the Standard Model. But does that mean that there are no new surprises to be found? Many EW processes have yet to be measured and are just starting to become accessible with the data collected at the LHC. Indeed, this unexplored region of EW physics may provide clues to as yet unknown new physics processes at higher energy scales. Using the 2012 LHC data recorded by the ATLAS experiment, we seek to make the first observation of one such EW process, the massive tri-boson final state: WWW. It represents one of the first searches to probe the Standard Model WWWW coupling directly at a collider. This search looks specifically at the channel where each W boson decays to a charged lepton and a neutrino, offering the best sensitivity for making such a measurement. In addition to testing the Standard Model directly, we also use an effective field theory approach to test for the existence of anomalous quartic gauge couplings which could offer evidence for new physics at higher energies than those produced by the LHC.