In this thesis, I study the electronic and structural phase diagrams of the superconducting 122 iron pnictides systems Ba1-xKx(Fe1-yCoy)2As2 and EuFe2(As1-xPx)2 by means of the local probe techniques 57Fe Mössbauer spectroscopy (MS) and muon spin relaxation (muSR). For both isovalent substitution strategies - Co/K for Fe/Ba and P for As, respectively - the antiferromagnetic Fe ordering and orthorhombic distortion of the parent compounds BaFe2As2 and EuFe2As2 are subsequently suppressed with increasing chemical substitution and superconductivity arises, once long-range and coherent Fe magnetic order is sufficiently but not entirely suppressed. For Ba1-xKx(Fe1-yCoy)2As2 in the charge compensated state (x/2=y), a remarkably similar suppression of both, the orthorhombic distortion and Fe magnetic ordering, as a function of increasing substitution is observed and a linear relationship between the structural and the magnetic order parameter is found. Superconductivity is evidenced at intermediate substitution with a maximum Tsc of 15 K coexisting with static magnetic order on a microscopic length scale. The appearance of superconductivity within the antiferromagnetic state can by explained by the introduction of disorder due to nonmagnetic impurities to a system with a constant charge carrier density. Within this model, the experimental findings are compatible with the predicted s± pairing symmetry. For EuFe2(As1-xPx)2, the results from 57Fe MS and ZF-muSR reveal an intriguing interplay of the local Eu 2+ magnetic moments and the itinerant magnetic Fe moments due to the competing structures of the iron and europium magnetic subsystems. For the investigated single crystals with x=0.19 and 0.28, 57Fe MS evidences the interplay of Fe and Eu magnetism by the observation of a transferred hyperfine field below Tafm at which the Eu subsystem orders into a canted A-type AFM magnetic structure. Furthermore, an additional temperature dependent out-of-plane tilting of the static Fe hyperfine field is observed below the onset of static Eu ordering. ZF-muSR shows a strong increase of the local field at the muon site below Tafm=20 K and a crossover from isotropic to anisotropic Eu spin-dynamics between 30 and 10 K. The temperature dependence of the spin dynamics, as derived from the muSR dynamic relaxation rates, are related to a critical slowing down of Eu-spin fluctuations which extends to even much higher temperatures (~100 K). They also effect the experimental linewidth observed in the 57Fe MS experiments. The strong influence of the Eu magnetic order onto the primary observables in both methods prevents conclusive interpretation of the experimental data with respect to a putative interplay of Fe magnetism and superconductivity.

La physique des oscillations de neutrinos occupe une place majeure dans les études s’intéressant à cetteparticule. Le mécanisme des oscillations, basé sur un changement d’état de saveur d’un neutrino durant sapropagation, permet d’élucider les déficits observés de neutrinos solaires et atmosphériques et apporte des indicationsintéressantes de physique au delà du Modèle Standard par l'étude des angles de mélanges et du schéma de masse desneutrinos.OPERA est un détecteur hybride combinant à la fois latechnique d'une détection électronique en temps réel et la technique de la chambre à brouillard à émulsion ou ECC(EmulsionCloud Chamber). Le détecteur ECC est un détecteur massif (cible) composé de 150000 briques dontchacune est constituée de feuilles de plombs, utilisées comme cible, alternées avec des émulsions nucléaires dont laprécision de reconstruction des traces est de l'ordre du micron. Le détecteur comprend également deux spectromètresavec des plaques de fer magnétisé de 5 cm d'épaisseur alternées avec les détecteurs RPC (Resistive Plate Chamber)associés à six ensembles de drift tubes (PT) pour la mesure de la charge et de l'impulsion du muon, et un plan de vetoservant à la rejection des particules extérieures à la cible. / The physics of neutrino oscillations plays a major role in studies concerned with cetteparticule. The mechanism of oscillations, based on a change of state of a neutrino flavor during sapropagation, elucidates the deficits observed solar and atmospheric neutrinos and provides indicationsintéressantes of physics beyond the Standard Model by studying the angles mixtures and mass desneutrinos.OPERA scheme is a hybrid sensor combining both latechnique an electronic real-time detection technology and the cloud chamber emulsion or ECC (EmulsionCloud chamber). The ECC is a solid detector detector (target) consisting of bricks dontchacune 150000 consists of sheets of lead, used as a target, with alternate nuclear emulsion whose traces laprécision reconstruction is of the order of one micron. The detector also includes two spectromètresavec magnetized iron plates 5 cm alternating with RPC (Resistive Plate Chamber) detectors associated with six sets of drift tubes (PT) to measure the charge and momentum of the muon thickness and plan vetoservant the rejection of foreign particles to the target.

Submitted by Luciana Ferreira (lucgeral@gmail.com) on 2018-06-08T14:31:19Z No. of bitstreams: 2 Tese - Stefano Castro Tognini - 2018.pdf: 57497993 bytes, checksum: 7f2bc280505dae763265dbf74341c9ca (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Approved for entry into archive by Luciana Ferreira (lucgeral@gmail.com) on 2018-06-08T14:44:34Z (GMT) No. of bitstreams: 2 Tese - Stefano Castro Tognini - 2018.pdf: 57497993 bytes, checksum: 7f2bc280505dae763265dbf74341c9ca (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Made available in DSpace on 2018-06-08T14:44:34Z (GMT). No. of bitstreams: 2 Tese - Stefano Castro Tognini - 2018.pdf: 57497993 bytes, checksum: 7f2bc280505dae763265dbf74341c9ca (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Previous issue date: 2018-04-26 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / The interaction of a cosmic ray particle with an element of the atmosphere results in a cascade of particles, known as extensive air showers, which can be divided into three main branches, known as the hadronic, the electromagnetic, and the muonic component. As for the latter, since muons can reach high depths underground, they are generally used to study cosmic rays at different underground depths. The dynamics of extensive air showers is directly connected to the density of the atmosphere, as it defines the probability of particles to decay or interact. As muons are mainly produced from the decay of pions and kaons, and a warmer atmosphere results in higher number of meson decays, such particles are prone to suffer a sea- sonality effect that is directly correlated to the yearly seasonal variations of the atmosphere, an effect that has been verified by a large number of experiments over the past six decades. In 2015 the MINOS experiment presented an anti correlation between the effective temperature of the atmosphere and the seasonality of the muon flux for multiplicities higher than one (i.e. more than one muon track per cosmic ray event). Said anti correlation is not yet fully understood, counting with only a qualitative hypothesis as a probable mechanism. As such, the main goals of this study are to verify the MINOS anti correlation effect and extend the study to verify the seasonality of the effect as a function of different variables in order to improve the understanding of the phenomenon and possible corroborations with the known hypothesis. Two full years of the NOνA Near Detector, ranging from April 2015 to April 2017, were used as the dataset for the analysis. The anti correlation between the multiple muon flux and the effective temperature of the atmosphere is confirmed by the NOνA Near Detector, being in full agreement with the results presented by the MINOS Collaboration. The seasonal effect is also broken down by different variables: i) track separation, ii) zenith angle, iii) track angular separation, and iv) multiplicity. Different regions of these variables represent different energy ranges for the detected underground muons, their hadron parents or the primary particles that originated the cosmic ray shower, being a way to verify any particular dependency with energy. The results show that there are no clear trends in any of the studied variables, except for the multiplicity, in which the intensity of the seasonal variation increases for higher multiplicities. / A interação entre um raio cósmico e algum elemento da atmosfera é responsável por produzir uma cascata de partículas, conhecida como chuveiro atmosférico extenso. Tal cascata pode ser dividida em três principais componentes, conhecidas como hadrônica, eletromagnética e muônica. O fato de que múons são capazes de alcançar grandes profundidades no subsolo, faz com que a última componente citada seja ideal para ser utilizada por detectores subterrâneos para estudar chuveiros atmosféricos extensos. A dinâmica desses chuveiros está diretamente associada à densidade da atmosfera, a qual é um fator determinante nas probabilidades de decaimento ou interação das partículas produzidas ao longo da mesma. Em vista do fato de que muons são produzidos à partir do decaimento de píons e káons, e considerando que uma atmosfera mais quente/fria implica em um maior/menor número de decaimento desses mésons, espera-se que o fluxo de múons de raios cósmicos tenha um sazonalidade anual, um efeito confirmado por um conjunto de experimentos ao longo das últimas 6 décadas. Em 2015 o experimento MINOS apresentou uma anticorrelação entre a temperatura efetiva da atmosfera e a sazonalidade do fluxo de múons para eventos com multiplicidade maior que um (ou seja, mais de uma trajetória detectada por evento de raio cósmico). Tal correlação inversa não é completamente compreendida, contando apenas com uma hipótese qualitativa como provável mecanismo físico. Portanto, os principais objetivos deste estudo implicam em verificar este efeito sazonal invertido no Near Detector do experimento NOνA, além de extender a verificação da sazonalidade de múons múltiplos em função de diferentes variáveis, de forma a trazer uma melhor compreensão sobre o fenômeno e trazer conclusões que possam corroborar com a hipótese mencionada anteriormente. Como forma de atingir os objetivos, desenvolveu-se uma análise usando dois anos de dados do NOνA Near Detector, acumulados entre abril de 2015 e abril de 2017. A anticorrelação entre o fluxo de múons múltiplos e a temperatura efetiva da atmosfera foi confirmada, estando de acordo com os resultados apresentados pelo experimento MINOS. O efeito sazonal foi estudado de acordo com diferente variáveis: i) separação entre trajetórias, ii) ângulo zenital, iii) separação angular e iv) multiplicidade. Diferentes regiões de valores destas variáveis representam diferentes regiões de energia dos múons detectados, dos hádrons que os originaram ou dos respectivos primários. Os resultados mostram que não existem claras correlações em nenhuma das variáveis estudadas, exceto pela multiplicidade, a qual mostra que a intensidade da variação sazonal de múons múltiplos aumenta à medida que a multiplicidade do evento aumenta.

Submitted by Renata Lopes (renatasil82@gmail.com) on 2017-07-04T20:35:11Z No. of bitstreams: 1 dayaneoliveiragoncalves.pdf: 5780108 bytes, checksum: 66585bbc9ff0f98a7f32499de344449c (MD5) / Approved for entry into archive by Adriana Oliveira (adriana.oliveira@ufjf.edu.br) on 2017-08-08T14:48:18Z (GMT) No. of bitstreams: 1 dayaneoliveiragoncalves.pdf: 5780108 bytes, checksum: 66585bbc9ff0f98a7f32499de344449c (MD5) / Made available in DSpace on 2017-08-08T14:48:18Z (GMT). No. of bitstreams: 1 dayaneoliveiragoncalves.pdf: 5780108 bytes, checksum: 66585bbc9ff0f98a7f32499de344449c (MD5) Previous issue date: 2017-04-11 / O calorímetro de Telhas (TileCal) é o calorímetro hadrônico central de um dos experimentos do Grande Colisor de Hádrons (LHC), o ATLAS. O TileCal fornece medidas de energia finamente segmentadas (10.000 canais de leitura) para as partículas incidentes no detector. Análises realizadas nos dados resultantes de colisões de partículas constataram que utilizar as informações da camada radial externa do TileCal, em coincidência com as câmaras de múons (MS) do ATLAS, pode proporcionar uma redução de falsos sinais de trigger (filtragem online) de múons gerados pelas iteração de prótons de baixo momento, na blindagem do feixe do LHC, com o MS. O projeto TileMuon foi desenvolvido para este propósito e sua principal atividade, no programa de atualização ATLAS, é habilitar o TileCal para fornecer as informações de trigger para a primeira etapa de filtragem online para a identificação de múons no ATLAS. Esta dissertação apresenta o estudo, o desenvolvimento e a implementação de uma técnica para a identificação de múons no contexto TileMuon. Técnicas de estimação encontradas na literatura foram aplicadas no contexto do projeto e comparadas. Os resultados para dados experimentais mostraram que o método para a identificação de múons, baseado no filtro casado para ruído gaussiano, obteve o melhor desempenho, em termos de erro de detecção, bem como viabilidade de implementação online, e foi a técnica escolhida para a aplicação. / The Tile Calorimeter (TileCal) is the central hadronic calorimeter of the ATLAS experiment at the Large Hadron Collider (LHC). TileCal provides highly-segmented energy measurements for incident particles. Information from TileCal’s outermost radial layer in coincidence with the ATLAS muon chambers can provide a reduction of the fake muon triggers due to slow charged particles (typically protons). The TileMuon project was development aims this purpose and its main activity of the Tile-Muon Trigger in the ATLAS upgrade program is to install and to activate the TileCal signal processor module for providing trigger inputs to the Level-1 Muon Trigger. This dissertation presents the study, the development and the implementation of the Muon identification techniqueinthe TileMuon context. Amplitude estimation techniques found in the literature were applied to the problem and confronted against each other. The results for experimental data shown that the Muon identification based on the maximum likelihood for Gaussian noise achieved the best performance in terms of detection error as well as online implementation feasibility, and it has been the chosen technique for the application.

La densité epsilon0 de la matière nucléaire ordinaire est de l'ordre de 0,17 GeV/fm^3 . Lorsqu’ elle atteint une densité comprise entre 5 à 10 epsilon0 ou une température comprise entre 150 à 200 MeV, une transition de phase, prédite par la ChromoDynamique Quantique sur réseau, vers un nouvel état de la matière se produit. Cet état dans lequel les quarks et les gluons sont déconfinés et peuvent se mouvoir librement est appelé Plasma de Quarks et de Gluons (PQG). Les collisions d’ions lourds ultra-relativistes au Large Hadron Collider (LHC) permettront de recréer les conditions de formation d’un tel état. L’étude du PQG au LHC se fera essentiellement avec l’expérience ALICE (A Large Ion Collider Experiment) dont le spectromètre à muons est conçu pour observer dans le canal muonique, sur un domaine de pseudo-rapidité -4 < eta < -2.5, la suppression des résonances lourdes (J/psi,Upsilon) par écrantage de couleur à travers leurs décroissance en muons.La première partie de ce travail porte sur les corrections d’acceptance et d’efficacité qui sont indispensables pour les analyses de physique. Cette étude a montré que le processus de correction est indépendant des distributions choisies.La seconde partie de cette thèse porte sur l’analyse du J/psi dans les collisions proton+proton à sqrt(s) = 7 TeV. / The ordinary nuclear matte density epsilon0 is around de 0,17 GeV/fm^3 . For a critical value between 5 and 10 epsilon0 or a temperature around 150 to 200 MeV, the lattice Quantum ChromoDynamics (lQCD) predicts a phase transition from the classical matter to a new state of matter called the Quark Gluon Plasma (QGP). In this state, quarks and gluons behave like free particles. Heavy ions collisions at the Large Hadron Collider (LHC) are used to recreate the condition needed for a QGP formation. ALICE (A Large Ion Collider Experiment) is one of the LHC experiment dedicated to the study the QGP. One of the possible signature is the suppression of the quarkonia (J/psi, Upsilon) by color screening. The ALICE muon spectrometer allows to measure the quarkonia, in a pseudo-rapidity domain -4 < eta < -2.5, using their decay into muons.The first part of the report presents the acceptance and efficiency corrections. These corrections are crucial for the analysis. This study has shown that the correction process is independent from the selected distribution used for the correction.The second part describes the analysis of the J/psi in proton+proton collisions at sqrt(s) = 7 TeV.

ALTO is a project, currently in the research and development phase, with the goal of constructing a Very High Energy (VHE) gamma-ray observatory in the southern hemisphere. It will detect the particle content reaching the ground from the interactions of either VHE gamma rays or cosmic rays in the atmosphere known as extensive air showers. In this thesis, we use an ALTO prototype built at Linneaus University to estimate the vertical muon intensity in Växjö. The atmospheric muons we detect at ground level come from hadronic showers caused by a cosmic ray entering the atmosphere. Such showers are considered background noise in the context of VHE gamma-ray astronomy, and the presence of muons is an important indicator of the nature of the shower, and thus of the primary particle. The measurement is done by isolating events that produce signals in two small scintillation detectors that are part of the ALTO prototype, and are placed almost directly above each other. This gives us a data set that we assume represents muons travelling along a narrow set of trajectories, and by measuring the rate of such events, we estimate the muon intensity. We estimate the corresponding momentum threshold using two different methods; Monte Carlo simulation and calculation of the mean energy loss. The vertical muon intensity found through this method is about 21% higher than commonly accepted values. We discuss some possible explanations for this discrepancy, and conclude that the most likely explanation is that the isolated data set contains a significant number of “false positives”, i.e., events that do not represent a single muon following the desired trajectory.

Unconventional superconductivity continues to be one of the most striking chapters in condensed matter physics, by posing challenges to our theoretical understanding of its origin. During the last three decades a large number of unconventional superconductors with exotic properties have been found arising great interest, such as the heavy fermion systems, high Tc cuprates as well as the Iron based superconductors etc. Sr2RuO4, the material I have studied, can be considered as an exemplary case in this regard. In spite of more than two decades of comprehensive research, Sr2RuO4 remains one of the most compelling superconductors till date. Various experimental results give evidence that the superconductivity of Sr2RuO4 is chiral: including measurements of the Kerr effect, sound velocities, critical currents across junctions, and muon spin relaxation(μSR), the experimental technique at the heart of this dissertation. Recent NMR Knight shift measurements suggests that the pairing is most likely spin-singlet, and in the tetragonal lattice of Sr2RuO4, the combination of singlet pairing and chirality compels consideration of an seemingly unlikely order parameter: dxz ± idyz. It is unlikely because it comes along with a horizontal line node at kz = 0, whereas Sr2RuO4 has a very low c-axis conductivity. And that makes the question whether or not the superconductivity of Sr2RuO4 is chiral, of great importance. This calls for an unique scenario in regard to our understanding of unconventional superconductivity, as the presence of chirality in Sr2RuO4 might imply a new form of pairing, which is yet to be firmly determined. Chiral superconductors break time reversal symmetry by definition, and in general time-reversal-symmetry breaking (TRSB) superconductivity indicates complex two component order parameters. Probing Sr2RuO4 under uniaxial pressure offers the possibility to lift the degeneracy between such components. However, despite strenuous efforts, a splitting of the superconducting and TRSB transitions under uniaxial pressure has not been observed so far. In this thesis, I report muon spin relaxation measurements on Sr2RuO4 samples, placed under uniaxial stress. The relatively large sample size suitable for μSR demanded for a customized uniaxial pressure cell in order to perform our experiments. It has been a technically challenging task to have a fully fledged uniaxial pressure cell with stringent requirements, that is suitable for time restricted facility experiments like μSR. The technical advancement has been documented thoroughly in this thesis. Using the dedicated uniaxial pressure cell, we observed the much awaited stress induced splitting between the onset temperatures of superconductivity and time reversal symmetry breaking, consistent with the qualitative expectations for a chiral order parameter in Sr2RuO4. In addition to that, we report the appearance of a bulk magnetic order in Sr2RuO4 under higher uniaxial stress for the first time, above the critical pressure at which a Lifshitz transition is known to occur. The signal in the state appearing at high stress qualitatively differs from that in the TRSB state in unstressed Sr2RuO4, which provides evidence that the enhanced muon spin relaxation at lower stresses is not a consequence of conventional magnetism. As a whole, our results strongly support the idea of two-component superconducting order parameter in Sr2RuO4, that breaks time-reversal symmetry.

In 2010, the Large Hadron Collider (\\lhc{}) at the European Organisation for Nuclear Research (CERN) near Geneva (Switzerland) came into full operation providing proton-proton collisions at a centre-of-mass energy of $\\sqrt{s} = \\unit[7]{TeV}$. \\lhc{} data may allow the observation of the Higgs boson, the last unknown building block of the standard model of particle physics (SM). Di-muon final states containing heavy flavour jets pose an irreducible background for searches of the Higgs boson as predicted the SM or theories beyond. They also provide a unique testbed for tests of perturbative Quantum Chromo-Dynamics (pQCD). This thesis provides a measurement of the cross section of events with one di-muon pair with an invariant mass in the \\Z{} mass region and at least one heavy flavour jet. Studies on acceptance and systematic effects of the experimental setup are presented as well as a comparison to theoretical predictions. The total inclusive cross section of \\zbFS{} events was observed as $\\sigma(\\mu^{+}\\mu^{-}+b+X) = \\unit[(4.15 ^{+0.97}_{-0.89} (stat.) ^{+0.45}_{-0.53} (syst.))]{pb} $ from the equivalent of $\\unit[36]{pb^{-1}}$ of data. Agreement with pQCD predictions at next-to leading order (NLO) is found while tensions with leading order (LO) predictions are observed. Further, the cross-section ratio \\RwZ{} with events containing two muons and at least one jet of any origin was measured to $\\mathcal{R} = \\unit[4.6 ^{+1.4}_{-1.2} (stat.) \\pm 0.5 (syst.)]{\\%}$. This is found to agree with NLO and LO calculations within known uncertainties.

This thesis presents a Monte Carlo study of neutral Higgs bosons of the Minimal Supersymmetric Standard Model (MSSM) decaying into muons at the Atlas experiment at the CERN Large Hadron Collider. Signal and background processes are simulated using novel Monte Carlo generators that incorporate parts of higher order corrections and are expected to give a more accurate prediction than previous programs. The SHERPA Monte Carlo generator is validated for its use in the analysis and compared to results obtained with other programs. Where possible, the Monte Carlo event samples are normalized to higher order calculations. To increase the available Monte Carlo statistics, this study is based on the ATLAS fast detector simulation ATLFAST. Differences between ATLFAST and the detailed detector simulation of ATLAS are examined, and, where possible, correction procedures are devised. A cut based analysis is performed assuming an integrated luminosity of 30 inverse femtobarns, and optimized with respect to the discovery potential for MSSM Higgs bosons. The systematic uncertainties of the event selection and the Monte Carlo predictions are estimated. A method that can be used to estimate the background from data is presented and evaluated. Last, the discovery potential of the \Atlas experiment in the CP conserving benchmark scenarios of the MSSM is evaluated. One or more of the neutral Higgs bosons of the MSSM can be discovered in the muonic decay mode using 30 inverse femtobarns of data for low masses of the pseudoscalar boson A, if the model parameter tan(beta) is at least 20. For higher masses of the A, tan(beta) would need to be significantly higher to ensure a discovery in the studied decay channel. The sensitivity of ATLAS to MSSM Higgs bosons is multiple times larger than the one of previous and currently running experiments. / Die vorliegende Arbeit präsentiert eine Monte Carlo Studie zu neutralen Higgs-Bosonen des Minimal Supersymmetrischen Standardmodells (MSSM) im myonischen Zerfallskanal am Atlas Experiment am Large Hadron Collider des CERN. Signal- und Untergrundprozesse werden mit neuartigen Monte Carlo Ereignisgeneratoren simuliert, die Teile der Korrekturen höherer Ordnung beinhalten, und von denen eine verbesserte Vorhersage erwartet wird im Vergleich zu herkömmlichen Programmen. Der SHERPA Monte Carlo Ereignisgenerator wird auf seine Brauchbarkeit für die Analyse überprüft und mit Ergebnissen anderer Programme verglichen. Sofern möglich werden die erstellten Monte Carlo Datensätze mittels Rechnungen zu höheren Ordnungen normiert. Um eine hinreichend große Statistik von simulierten Daten zu erhalten, wird die schnelle Detektorsimulation des ATLAS Detektors ATLFAST verwendet. Unterschiede zwischen der vollständigen Detektorsimulation und ATLFAST werden untersucht, und sofern möglich, Korrekturverfahren entwickelt. Eine schnittbasierte Analyse wird durchgeführt unter der Annahme einer integrierten Luminosität von 30 inversen femtobarn und optimiert mit Hinblick auf das Entdeckungspotenzial für MSSM Higgs-Bosonen. Die systematischen Unsicherheiten der Ereignisauswahl und der Monte Carlo-Vorhersagen werden abgeschätzt. Eine Methode zur Messung des Untergrundes in Daten wird vorgestellt und überprüft. Schliesslich wird das Entdeckungspotenzial des ATLAS Experiments in Vergleichspunkten für CP erhaltende Szenarien des MSSM ermittelt. F\ür niedrige Massen des pseudoskalaren Higgs-Bosons A kann mindestens eines der neutralen Higgs-Bosonen des MSSM im myonischen Zerfallskanal entdeckt werden, sofern der Modellparameter tan(beta) mindestens 20 ist. Für hohe Massen des A muss ein wesentlich größeres tan(beta) in der Natur realisiert sein, um eine Entdeckung im untersuchten Zerfallskanal zu ermöglichen. Die Sensitivität von ATLAS auf Higgs-Bosonen des MSSM ist um ein Vielfaches höher als diejenige bisheriger oder momentan laufender Experimente.

La physique des particules élémentaires, aussi appelé physique des hautes énergies, est l'étude de l'infiniment petit, popularisée récemment par la découverte de nouvelles particules fondamentales permettant de consolider notre connaissance de la matière. Pour réaliser des mesures à une échelle aussi réduite, une méthode consiste à augmenter l’énergie des constituants de la matière, à l'aide d'accélérateur de particules, puis de les briser pour révéler leur constitution. Au-delà de l'intérêt en termes de physique expérimentale, réaliser des expériences de ce type est devenu une prouesse technologique grandissante avec les niveaux d’énergie atteints. La complexité de l’expérience CMS, cadre dans laquelle ce travail a été réalisé, donne une bonne mesure des défis technologiques relevés.<p>Afin d'affiner encore notre connaissance des processus mis en jeu lors collision de particules dans CMS, une mise à niveau du détecteur est prévue avant la fin de cette décennie. Certains sous-détecteurs actuellement installés, et notamment le spectromètre à muon dans la zone des bouchons, sont d’ores et déjà identifiés comme offrant des performances trop faibles pour l'augmentation du nombres d’événements prévu après cette mise à jour. Ce travail propose de réaliser une étude de faisabilité sur l'utilisation d'une technologie alternative pour ce sous-détecteur, notamment le Triple-GEM, pour combler ces limitations.<p>Une première partie de ce travail consiste en l'étude de cette nouvelle technologie de détecteur à gaz. Cependant, la mise en œuvre de cette technologie conduit à des modifications dans le système d'acquisition de données de CMS. La situation actuelle puis les implications d'un point de vue technique des modifications sont donc détaillées par la suite. Enfin, après avoir identifié les composants et les solutions permettant la collecte de résultats à l’échelle de l'ensemble du sous-détecteur, un système d'acquisition de données similaire a été réalisé et est décrit dans une dernière partie de ce travail. / Doctorat en Sciences / info:eu-repo/semantics/nonPublished