Cette thèse porte sur deux aspects de l'International Linear Collider (ILC) qui est un projet d'un collisionneur linéaire électron-positron avec une énergie dans le centre de masse pouvant aller jusqu'à 500 GeV.Le premier aspect est l'élaboration d'un calorimètre électromagnétique silicium-tungstène (SiW-ECAL) pour l'un des détecteurs de l'ILC. Le concept de ce détecteur est piloté par les spécifications du faisceau de l'ILC et par l'algorithme du Particle Flow (PFA). Cela nécessite un calorimètre hautement granulaire et très compact avec l'électronique directement intégrée à l'intérieur. Pour prouver les capacités du SiW-ECAL, un prototype technologique a été construit et testé en faisceau de test à DESY. Les résultats sont présentés ici et montrent, après la procédure de calibration, un signal sur bruit de 10, même en mode power pulsing.Le deuxième aspect est l'étude de l'un des canaux physique importants de l'ILC, la production de pairs de quark top anti-top. L'objectif principal de cette étude est de déterminer la précision que nous pouvons attendre à l'ILC sur le couplage du top avec le boson W et le photon. Pour obtenir cette précision différentes observables sont utilisées, la section efficace, l'asymétrie avant-arrière et la distribution d'hélicité de la production de pairs de quark top anti-top. L'analyse est basée sur les événements avec des faisceaux polarisés et reconstruit avec la simulation complète du détecteur ILD, qui est le détecteur du SiW-ECAL, pour le Detector Baseline Design de l'ILD. Au final l'erreur attendue sur le couplage du quark top est de l'ordre de 2%. / This thesis deals with two aspects of the International Linear Collider (ILC) which is a project of a linear electron-positron collider of up to at least 500 GeV center of mass energy.The first aspect is the development of a silicon-tungsten electromagnetic calorimeter (SiW-ECAL) for one of the detectors of the ILC. The concept of this detector is driven by the ILC beam specifications and by the Particle Flow Algorithm (PFA). This requires highly granular calorimeter and very compact one with integrated electronics. To prove the capability of the SiW- ECAL a technological prototype has been built and tested in test beam at DESY. The results are presented here, and show, after the calibration procedure a signal over noise ratio of 10, even in the power pulsing mode.The second aspect is the study of one of the important physics channels of the ILC, the top anti-top quark pairs production. The main goal of this study is to determine the precision that we can expect at the ILC on the top coupling with the W boson and the photon. To get this precision differents observables are used, the cross- section, the forward- backward asymmetry and the helicity distribution of the top anti-top quark pairs production. The analysis is based on the events with polarized beams and reconstructed with the full simulation of the ILD detector, which is the detector of the SIW- ECAL, for the Detector Baseline Design of the ILD. The final expected errors on the top coupling is of the order of 2%.

Le travail de doctorat exposé dans ce manuscrit a été développé dans le cadre du projet LUMINEU, une expérience pilote pour la double désintégration bêta sans émission de neutrinos (0νββ) de l'isotope Mo avec des bolomètres scintillants de ZnMoO₄. Ce travail de physique expérimentale implique l'avancement du design et des tests des prototypes de détecteurs, et le développement des outils en vue de la préparation d'une expérience importante. La méthode de détection adoptée dans cette thèse est la technique bolométrique, qui s'intègre bien avec les caractéristiques requises des détecteurs pour étudier les événements rares. Le détecteur fournit une grande efficacité, une très bonne résolution en énergie et il permet la discrimination des particules pour la suppression du fond. Cette thèse se concentre sur la physique du neutrino et sur la désintégration 0νββ; les méthodes de détection expérimentales et la sensibilité de la demi-vie d'une expérience 0νββ sont traitées.La deuxième partie de ce travail est dédiée au setup, l'acquisition et l'analyse des données sont traitées en détails.La dernière partie de la thèse est consacrée aux résultats : les progrès réalisés dans le détecteurs bolométriques et les mesures sont résumés. Sur la base de ces résultats, nous avons calculé une sensibilité finale sur une expérience à venir basée sur ces détecteurs. / The current experiments on rare events searches for neutrino and dark matter are at present two of the most relevant and exiting field in particle and astro-particle physics.Thanks to the efforts made in the past years, much of progress has been made in answering some big open questions in this field. In particular, experiments in neutrino physics during the past decades gave very interesting results, stimulating new ideas of the mechanisms beyond the Standard Model. One of them is known as neutrinoless double beta decay which can give important informations on the puzzling picture of how nature behaves. It is a rare nuclear transition with a half life longer than 10^25 years where two neutrons decay simultaneously in to two protons with the emission of only two electrons, the two neutrino acting as a virtual particle between the two decay vertices. This process is possible only if the neutrino is equal to its antiparticle, which is in contrast with the SM predictions.The observation of this phenomenon can determining the nature -- Dirac or Majorana --, of massive neutrinos. This is of fundamental importance for making progress in our understanding of the origin of neutrino masses and mixing and of the symmetries governing the lepton sector of particle interactions. The measurement of the half life of the process would give unvaluable information on the absolute scale of neutrino masses, the Majorana phases and the type ofneutrino mass spectrum.This thesis is deeply related to the LUMINEU project aiming to prepare the construction of a next-generation Neutrinoless Double Beta Decay experiment, capable exploring the inverted hierarchy region of neutrino mass. This goal will be achieved through the development of sophisticated low-temperature detectors named bolometers, which may lead to important advancements in the field of dark matter detection as well.Bolometers are low temperature calorimetric detectors, which can exploit the so called homogeneous approach, which provides very high efficiency. They can be made by almost any dielectric material, giving a flexibility in the source/detector material choice. In addition, their excellent energy resolution makes them very competitive detectors.Scintillating bolometers are upgrade of the simple bolometers, where the absorber can also scintillate. The readout of the scintillating light is made by an auxiliary bolometer and it enables particle identification with the only drawback of doubling the readout channels.In this context, we developed, tested and optimized scintillating bolometers and innovative light detectors for a pilot underground experiment on neutrinoless double beta decay of 100Mo embedded in ZnMoO₄ and Li₂MoO₄ crystal scintillators.We demonstrated that the sensitivity of an experiment searching for neutrinoless double beta decay with scintillating bolometers can compete with reach the present forefront technologies in the field.

L'étude présentée dans cette thèse est dédiée à l'analyse des désintégrations radiatives de mésons beaux, processus faisant intervenir le quark b ce dernier se désintégrant par interaction faible en un quark s avec émission d'un photon. Ce type de désintégration est interdit à l'arbre en théorie quantique des champs et doit donc s'opérer à l'aide de boucles. Ces désintégrations ont des rapports d'embranchement très faibles, de l'ordre de 10^{-5}. Dès lors, l’étude de ces processus à l'aide du détecteur LHCb permet de mesurer précisément des observables reliées à ces processus, telles que les rapports d'embranchement, les asymétries de CP ou des variables angulaires et d'hélicité comme la polarisation du photon. En comparant ces résultats expérimentaux avec les prédictions théoriques du Modèle Standard de la Physique des Particules, il devient possible de tester ce modèle et de contraindre l'existence d'une nouvelle physique au delà du Modèle Standard. L'analyse présentée dans cette thèse se concentre sur l'étude des désintégrations B0 -> K*0 gamma, Bs0 -> phi gamma et Bs0 -> K*0 gamma. Les événements utilisés sont ceux où le photon s'est converti en une paire électron-positron par interaction avec le détecteur afin de bénéficier de la bonne résolution sur l'impulsion des traces chargées des trajectographes de LHCb. Les mesures du rapport des rapports d'embranchement des désintégrations B0 -> K*0 gamma et Bs0 -> phi gamma ainsi que de l'asymétrie de CP directe dans le processus B0 -> K*0 gamma sont réalisées. La bonne résolution obtenue sur la masse du méson B0 a permis de déterminer une première limite supérieure au rapport d'embranchement de la désintégration supprimée de Cabbibo Bs0 -> K*0 gamma. / The purpose of the work presented in this thesis is to study the radiative decays of B mesons. These processes correspond to the decay of a b-quark into a s-quark through the weak interaction with a photon in the final state. This kind of decay is not allowed at tree level in the quantum field theory but only through virtual loops. These processes have small branching fractions of the order of 10^{-5}. The study of these decays with the LHCb detector provides precise measurements of related observable such as branching fractions, CP asymmetries or angular variables such as the photon polarisation. These results can be compared with the theoretical prediction of the Standard Model of Particle Physics. Therefore, it is possible to test this model and to constrain the existence of new physics behind the Standard Model. The analysis presented in this thesis focuses on the B0 → K*0 gamma, Bs0 → phi gamma and Bs0 → K*0 gamma decays. Only events where the photon has converted into a dielectron pair by interacting with the detector are used. This allows to take advantage of the good resolution on the charged tracks momentum obtained with the LHCb's tracking system. The measurements of the ratio of branching fractions of the B0 → K*0 gamma and Bs0 → phi gamma decays and of the direct CP asymmetry in the B0 → K*0 gamma process are performed. The good resolution obtained on the B meson mass allows to set the first upper limit on the branching ratio of the Cabbibo suppressed Bs0 → K*0 gamma decay.

Submitted by Daniella Santos (daniella.santos@ufma.br) on 2017-10-04T14:57:37Z No. of bitstreams: 1 FabianoSimas.pdf: 1533418 bytes, checksum: 83eb429346cc89e3e1a7b9309cde9761 (MD5) / Made available in DSpace on 2017-10-04T14:57:37Z (GMT). No. of bitstreams: 1 FabianoSimas.pdf: 1533418 bytes, checksum: 83eb429346cc89e3e1a7b9309cde9761 (MD5) Previous issue date: 2011-08-29 / FAPEMA / In this work we consider rings constructed with a scalar field ϕ with radial symmetry embedded in the (3, 1) Minkowski spacetime. Such topological defects have radius and thickness related to the energy density and can be attained from a lagrangian density explicitly dependent with the distance,which can be interpreted as an effective theory from a more fundamental model. Neglecting the backreaction on a weak scalar field Φ coupled with the strong field ϕ, a standard mode decomposition leads to a standard action for one-dimensional Klein-Gordon fields living along the ring axis and a two-dimensional Schr¨odinger-like equation, describing massive spin-0 particles. A specific choice of the coupling between the scalar fields Φ and ϕ is able to transform the Schr¨odinger-like equation in a one-dimensional form depending on the radial distance. The interaction is compatible with a repulsive character of the core of the ring and with the presence of resonances around the ring radius. The presence of tachyonic and physical modes are described in a phase space diagram, which is confronted with the numerical analysis of the massive modes. It is found that, for the scale of rings considered, larger radius favor the localization process, and for small radius the leaking of the massive modes is compatible with a repulsive interaction acting between the rings walls and the massive spin-0 particles. / Neste trabalho nós consideramos anéis construídos com um campo escalar ϕ com simetria radial imerso no espaço-tempo de Minkowski-(3, 1). Tais defeitos topológicos tˆem raio e espessura relacionados com a densidade de energia e podem ser obtidos a partir de uma densidade lagrangeana explicitamente dependente da distância, o que pode ser interpretada como uma teoria efetiva a partir de um modelo mais fundamental. Negligenciando a backreaction em um campo escalar fraco Φ acoplado com o campo forte ϕ, um modo padrão de decomposição leva `a uma ação padrão para os campos de Klein-Gordon 1-dimensional vivendo ao longo do eixo do anel e uma equação do tipo Schrödinger 2-dimensional, descrevendo partículas massivas de spin-0. Uma escolha especificado acoplamento entre os campos escalares Φ e ϕ é capaz de transformar a equação do tipo Schrödinger em uma forma 1-dimensional dependendo da distância radial. A interação e compatível com um caráter repulsivo do núcleo do anel e com a presença de ressonâncias ao redor do raio do anel. A presença taquiônica e modos físicos são descritos em um diagrama de espaço de fase, que é confrontado com a análise numérica dos modos massivos. Verifica-se que, para a escala de an´eis considerados, raios maiores favorecem o processo de localiza¸c˜ao e quanto aos anéis de raios menores, o vazamento dos modos massivos é compatível com uma interação repulsiva agindo entre as paredes do anel e as partículas massivas de spin-0.

This thesis deals with two aspects of the International Linear Collider (ILC) which is a project of a linear electron-positron collider of up to at least 500 GeV center of mass energy.The first aspect is the development of a silicon-tungsten electromagnetic calorimeter (SiW-ECAL) for one of the detectors of the ILC. The concept of this detector is driven by the ILC beam specifications and by the Particle Flow Algorithm (PFA). This requires highly granular calorimeter and very compact one with integrated electronics. To prove the capability of the SiW- ECAL a technological prototype has been built and tested in test beam at DESY. The results are presented here, and show, after the calibration procedure a signal over noise ratio of 10, even in the power pulsing mode.The second aspect is the study of one of the important physics channels of the ILC, the top anti-top quark pairs production. The main goal of this study is to determine the precision that we can expect at the ILC on the top coupling with the W boson and the photon. To get this precision differents observables are used, the cross- section, the forward- backward asymmetry and the helicity distribution of the top anti-top quark pairs production. The analysis is based on the events with polarized beams and reconstructed with the full simulation of the ILD detector, which is the detector of the SIW- ECAL, for the Detector Baseline Design of the ILD. The final expected errors on the top coupling is of the order of 2%.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / O presente trabalho trata do estudo, por meio de simulação de Monte Carlo, de correlações entre variáveis cinemáticas nas topologias de difração simples e de dupla troca de pomeron com vista a delimitar e estudar o espaço de fase referente às topologias citadas, em especial no que se refere á produção inclusiva de dijatos no contexto do experimento CMS/LHC. Será também apresentada uma análise da produção, por difração simples, de dijatos inclusivos a energia no centro de massa √s = 14 TeV (também por simulação de Monte Carlo), na qual estabelecemos um procedimento, a ser usado com dados, para a observação desse tipo de processo. Ainda analisamos a influência de diversos valores da probabilidade de sobrevivência do intervalo de rapidez, [|S|], nos resultados, de forma que com 10 pb -1 de dados acumulados, uma simples observação da produção de dijatos difrativos inclusivos, pelo método proposto, pode vir a excluir valores muito pequenos de [|S|]. / This work is about the study, by means of a Monte Carlo simulation, of correlations in kinematical variables on topologies of single diffraction and double pomeron exchange looking for determinate and study the phase space of the cited topologies, specially in what is about inclusive production of dijets at CMS/LHC. It will be also presented an analysis on the single diffractive production of inclusive dijets at center of mass energy √s = 14 TeV (also bymeans of a Monte Carlo simulation), in which we established a data-driven procedure, for the observation of this kind of process. We also analyze the impact of different values of rapidity gap survival probability, [|S|], on the results, in such a way that we can conclude that an observation of inclusive diffractive dijets, in 10 pb-1 of data, using the procedure proposed, may exclude very low values of [|S|].

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / O presente trabalho trata do estudo, por meio de simulação de Monte Carlo, de correlações entre variáveis cinemáticas nas topologias de difração simples e de dupla troca de pomeron com vista a delimitar e estudar o espaço de fase referente às topologias citadas, em especial no que se refere á produção inclusiva de dijatos no contexto do experimento CMS/LHC. Será também apresentada uma análise da produção, por difração simples, de dijatos inclusivos a energia no centro de massa √s = 14 TeV (também por simulação de Monte Carlo), na qual estabelecemos um procedimento, a ser usado com dados, para a observação desse tipo de processo. Ainda analisamos a influência de diversos valores da probabilidade de sobrevivência do intervalo de rapidez, [|S|], nos resultados, de forma que com 10 pb -1 de dados acumulados, uma simples observação da produção de dijatos difrativos inclusivos, pelo método proposto, pode vir a excluir valores muito pequenos de [|S|]. / This work is about the study, by means of a Monte Carlo simulation, of correlations in kinematical variables on topologies of single diffraction and double pomeron exchange looking for determinate and study the phase space of the cited topologies, specially in what is about inclusive production of dijets at CMS/LHC. It will be also presented an analysis on the single diffractive production of inclusive dijets at center of mass energy √s = 14 TeV (also bymeans of a Monte Carlo simulation), in which we established a data-driven procedure, for the observation of this kind of process. We also analyze the impact of different values of rapidity gap survival probability, [|S|], on the results, in such a way that we can conclude that an observation of inclusive diffractive dijets, in 10 pb-1 of data, using the procedure proposed, may exclude very low values of [|S|].

Dans cette thèse sont présentées plusieurs études relatives aux désintégrations de mésons Bd et Bs en trois corps sans charme avec un KS dans l'état final.Ces analyses portent sur des données collectées par l'expérience LHCb durant le Run I du LHC, et qui correspondent à une luminosité intégrée de 3 fb-1.Une première analyse consiste à la mesure des rapports d'embranchements des modes B(d,s) -> KSh+h'-, ou h(') désigne un kaon ou un pion.Les mesures précédemment effectuées par LHCb de ces rapports d'embranchement, relativement à celui du mode Bd->KSpi+pi-, sont actualisées.Le but principal de cette analyse est la recherche du mode Bs -> KSK+K-, qui n'a jamais encore été observé.Les rapports d'embranchements, relativement à celui de Bd -> KSpi+pi-, sont mesurés : B(Bs->KSpi+pi-)/B(Bd->KSpi+pi-) = 0.26 +/- 0.04(stat.) +/- 0.02(syst.) +/- 0.01(f_s/f_d) B(Bd->KSKpi)/B(Bd->KSpi+pi-) = 0.17 +/- 0.02(stat.) +/- 0.00(syst.) B(Bs->KSKpi)/B(Bd->KSpi+pi-) = 1.84 +/- 0.07(stat.) +/- 0.02(syst.) +/- 0.04(f_s/f_d) B(Bd->KSKK)/B(Bd->KSpi+pi-) = 0.59 +/- 0.02(stat.) +/- 0.01(syst.)Une première observation de Bs->KSK+K-, correspondant à une significance globale de 3.7 sigmas, est effectuée.Une analyse du plan de Dalitz indépendante du temps et sans étiquetage de saveur du canal Bd -> KSK+K- est effectuée en utilisant l'approche isobare.Les rapports d'embranchement des désintégration quasi-deux-corps des canaux Bd->KS phi, Bd->KS f'2(1525) et Bd->KS chic0 sont mesurés.Ils sont compatibles avec des mesures précédentes effectuées par Babar. / This dissertation presents several studies of the decays of both Bd and Bs mesons to charmless three-body final states including a KS meson.They use the data recorded by the LHCb experiment during Run I of LHC, corresponding to an integrated luminosity of 3 fb-1.A first analysis consists of the measurement of the branching fractions of B(d,s)->KSh+h'- decays, where h(') designates a kaon or a pion.Preceding LHCb measurements of branching fractions for all decay channels, relative to that of Bd->KSpi+pi-, are updated.Furthermore, the primary goal of this analysis is to search for the, as yet, unobserved decay Bs->KSK+K-.The relative branching fractions are measured to be: B(Bs->KSpi+pi-)/B(Bd->KSpi+pi-) = 0.26 +/- 0.04(stat.) +/- 0.02(syst.) +/- 0.01(f_s/f_d) B(Bd->KSKpi)/B(Bd->KSpi+pi-) = 0.17 +/- 0.02(stat.) +/- 0.00(syst.) B(Bs->KSKpi)/B(Bd->KSpi+pi-) = 1.84 +/- 0.07(stat.) +/- 0.02(syst.) +/- 0.04(f_s/f_d) B(Bd->KSKK)/B(Bd->KSpi+pi-) = 0.59 +/- 0.02(stat.) +/- 0.01(syst.) A first observation of Bs->KSK+K- is reported with a global significance of 3.7 sigmas.A flavour-untagged, time-independent Dalitz-plot analysis of Bd->KSK+K- is presented, using the isobar approach.The quasi-two-body branching fractions of Bd->KS phi, Bd->KS f'2(1525), and Bd->KS chic0 are measured.They are compatible with previous measurements from Babar.

Suite à la détection du très attendu boson de Higgs, le Grand Collisionneur de Hadrons (LHC) ainsi que le détecteur ATLAS se prépare pour une importante mise à niveau. Prévu pour le LHC à Haute Luminosité (HL-LHC), le ITk (Inner TracKer), un trajectomètre pour particules chargées fait de silicium, est la mise à niveau du détecteur interne du détecteur ATLAS. Une phase de test des modules de détecteur du ITk est cruciale puisque le détecteur sera inaccessible pour environ 10 ans suite à l’installation. Ce mémoire se concentrera sur les tests effectués sur un sous-ensemble du détecteur ITk, soit le détecteur ITk Strip. Pour détecter les bris prématurés sur les 20 000 modules qui seront produits, une procédure de cyclage thermique sera mise en oeuvre, où les modules seront refroidis et réchauffés pour recréer les 10 ans d’opération. Ces tests seront effectués dans une enceinte appelé coldbox. Le thème de ce mémoire est le calcul du stress mécanique dans les modules ITk Strip induit par la procédure de cyclage thermique à l’aide de la méthode des éléments finis. Le premier résultat obtenu est que le stress induit dans le module installé dans le coldbox est causé par le vide appliqué sous le module pour le tenir en place. De plus, le stress maximal durant le cyclage thermique est grandement dépendant de l’épaisseur du joint sous-vide utilisé. Ainsi, un joint plus mince cause un stress plus faible. Finalement, le stress dans le coldbox est entre 20 MPa et 100 MPa variant avec l’épaisseur du joint, ce qui est en accord avec le stress calculé pour une disposition semblable au détecteur final, donnant un stress de 64.8MPa. Il est donc possible de conclure que le coldbox est un bon candidat pour effectuer le cyclage thermique. / Following the great achievement by the ATLAS experiment at the Large Hadron Col- lider (LHC) that is the detection of the long-awaited Higgs boson, an upgrade of the LHC is planned, requiring an upgrade of ATLAS. Planned for the High-Luminosity LHC, the ITk (Inner TracKer), an all-silicon charged particle tracker, is the upgrade of the current ATLAS Inner Detector. Testing of the detector modules comprised in the ITk is crucial because the detector will be inaccessible for approximately 10 years following the installation. In this thesis, the focus will be kept on a subset of the ITk detector, namely the ITk Strip detector. To detect premature failure in the 20 000 Strip modules that will be produced, a series of tests will be performed, one of which will be the thermal cycling, where modules are monitored while being thermally cycled to replicate 10 years of operating conditions. These tests will occur in a special enclosure known as a coldbox. The subject of this work is to study the induced mechanical stress in future ITk Strip detector modules due to thermal cycling using Finite Element Analysis. Our first result is that the stress created in the module is mostly due to the vacuum applied to hold the module. Moreover, the maximum stress felt during thermal cycling is highly dependent on the thickness of the vacuum seal used: A thinner seal causes a lower stress. Finally, the stress in the module in our thermal cycling setup is between ∼ 20 MPa and ∼ 100 MPa depend- ing on the selected seal thickness, which is consistent with the stress expected in the final detector design which is approximately 64.8MPa. We can then conclude that the proposed design for the coldbox is a good candidate to perform thermal cycling.