Na primeira parte do trabalho estudamos a produção de léptons pesados através do mecanismo de fusão de glúons, assumindo a extensão supersimétrica mínima do modelo padrão. Nós mostraremos que para altos valores de tan a seção de choque é aumentada em relação ao modelo padrão, o que acarreta um número grande de eventos, permitindo extrair o sinal de background. Na segunda parte nós estudamos os sinais dos leptoquarks vetoriais em aceleradores E+ E- através de seus efeitos sobre a produção de um par de jatos, assim como sua produção isolada e sua produção em pares. Por último investigamos a produção de leptoquarks vetoriais em aceleradores hadrônicos, bem como sinais indiretos de existência destas partículas. / In the first parto f the work, we study the production of heavy lepton assuming the minimal supersymetric standard model. We show that for large values of tan , the cross-section is enhanced in comparison with standard model, and that it is possible to have a large number of events, allowing to extract the signal from the background. In the second part we study the signal for composite vector leptoquarks in E+ E- colliders (LEP II, NLC and CLIC) trough their effects on the production of jet pairs, as well as their single and pair productions. Finally we investigate a production of vector leptoquarks in pp(pp) colliders, as well as indirect signals for existence of these particles.

O experimento SELEX-E781, no Fermilab, coletou 15 bilhões de interações hadrônicas durante os 18 meses de tomada de dados, (Fevereiro-96 a Setembro 97), usando um feixe secundário de 600 GeV/c, composto 50 % - e 50% - e feixe de prótons a 500 GeV/c em alvos de cobre e carbono, com o propósito de estudar a produção e decaimentos de partículas contendo o quark charme. Neste trabalho são apresentados resultados da produção inclusiva do bárion charmoso \'A IND.C\'+ e anti-bárion \'A IND.C\'- decaindo em \'A IND.C\' pK. Mais especificamente, medem-se os parâmetros resul- tantes dos ajustes das distribuições corrigidas do \'A IND.C\'+ e estado conjugado de carga, em função das variáveis cinemáticas, xF e o quadrado do momento transversal (\'p POT.2\'), por funções fenome- nológicas conhecidas na literatura. Uma amostra de 2500 ± 90 \'A IND.C\'\'s (e conjugado de carga) foi extraída após a aplicação de todos os critérios de seleção de eventos. São feitas discussões sobre relações entre os números quânticos de sabor do feixe e da partícula produzida. Grandes valores de assimetrias entre \'A IND.C\'+ e \'A IND.C\'- em função do momento longitudinal, são medi- dos para feixes de bárions enquanto que um pequeno valor e encontrado para o feixe de mé- sons. Os dados, quando possível, são também comparados a outras medidas realizadas em experimentos de hadroprodução anteriores. / The SELEX experiment at Fermilab took data during 18 months (February 96 - September 97) and collected approximately 15 billion hadronic interactions, using a 600 GeV/c secondary beam with equal amounts of - and - and 500 GeV/c próton beam on copper and carbon tar gets to study the production and decay of particles containing a charm quark. In this work results are presented on the inclusive production of the Ac+ and Ac- charm baryon where the Ac is reconstructed from its decay into pK. Specifically, we extract parameters of phenomenological models from fits to the acceptance corrected distributions of the Ac+ and charge conjugate, as a function of kinematic variables such as scaled longitudinal momentum (xF ) and transference moment squared (p2t ). A sample of 2500 ± 90 cs (and charge conjugate) was extracted in the course of the selection criteria. Correlations between the flavor quantum number of the beam and the produced particle are discussed. Large values of the asymmetry between Ac+ and Ac- as a function of xF, are obtained for baryon beam. In contrast, small asymmetry is found for the pion beam. The results are also compared to previous measurements by other experiments which used a - and - beam

Na primeira parte do trabalho estudamos a produção de léptons pesados através do mecanismo de fusão de glúons, assumindo a extensão supersimétrica mínima do modelo padrão. Nós mostraremos que para altos valores de tan a seção de choque é aumentada em relação ao modelo padrão, o que acarreta um número grande de eventos, permitindo extrair o sinal de background. Na segunda parte nós estudamos os sinais dos leptoquarks vetoriais em aceleradores E+ E- através de seus efeitos sobre a produção de um par de jatos, assim como sua produção isolada e sua produção em pares. Por último investigamos a produção de leptoquarks vetoriais em aceleradores hadrônicos, bem como sinais indiretos de existência destas partículas. / In the first parto f the work, we study the production of heavy lepton assuming the minimal supersymetric standard model. We show that for large values of tan , the cross-section is enhanced in comparison with standard model, and that it is possible to have a large number of events, allowing to extract the signal from the background. In the second part we study the signal for composite vector leptoquarks in E+ E- colliders (LEP II, NLC and CLIC) trough their effects on the production of jet pairs, as well as their single and pair productions. Finally we investigate a production of vector leptoquarks in pp(pp) colliders, as well as indirect signals for existence of these particles.

Heavy quark decays provide a very advantageous investigation to test the Standard Model (SM). Recently, promising experiments with b quark, as well as the analysis of the huge data sets produced at the Large Hadron Collider(LHC) experiment, have led to an increasing study and sensitive measurements of relative b quark decays. In this thesis, a preliminary study is presented for the first time observation of the B+ → ψ(2S)φK+ with a statistical significance above 5 standard deviations using proton-proton collisions at √s = 8 TeV collected with CMS detector at LHC. The data sample, selected on the basis of the dimuon decay mode of the ψ(2S), corresponds to an integrated luminosity of 19.6 fb−1. A total of 140±15 B+ → ψ(2S)φK+ events have been observed. The branching fraction of B+ → ψ(2S)φK+ is measured relative to B+ → ψ(2S)K+, whose absolute branching fraction (BF) is known. The ratio is converted to an absolute branching fraction of B+ → ψ(2S)φK+, including systematics which is determined to be (4.0 ± 0.4(stat) ± 0.6(syst) ± 0.1(BR)) × 10−6, where the third uncertainty is due to imprecise knowledge of BF. The upper limit of the fraction of B+ → ψ(2S)(non−φ)K+ component in the selected B+ → ψ(2S)K+K−K+ channel is found to be 26% at 95% confidence level.

Supersymmetry is an attractive extension of the standard model of particle physics. It associates to every bosonic degree of freedom a fermionic one and vice versa. Supersymmetry unifies the coupling constants of the electromagnetic, weak and strong forces at a high scale and provides a candidate for the elusive dark matter. Supersymmetry could be discovered at the LHC, the proton--proton collider at CERN which has started operations in 2008. The LHC is foreseen to have a center--of--mass energy of 14~TeV, opening up a new mass range to be explored to search for supersymmetric particles with the ATLAS and CMS experiments. The development and production of electronics for these detectors has been a challenge, e.g. for the readout board for the electromagnetic calorimeter. Reconstructing the physics events with the best precision, in particular the reconstruction and identification of electrons and photons in the large QCD background has been prepared in extensive test beam studies and Monte Carlo simulations. If the Higgs boson and supersymmetry are discovered, the properties of the (s)particles such as the masses, branching ratios must be measured precisely, either at the LHC or at a future e+e- linear collider. The SFitter project aims to determine the underlying theoretical model parameters from the correlated experimental measurements including theoretical errors. The methods are applied to the extraction of the fundamental parameters of supersymmetry as well the measurement of the Higgs boson couplings at the LHC. The extrapolation of the supersymmetric parameters from the weak scale to the Grand Unification Scale could provide the basis towards the inclusion of gravity.

Les états quantiques du neutron dans le champ de pesanteur offrent une situation unique ou on mesure un phénomène quantique associe à la gravitation. Les neutrons qui rebondissent sous l'effet de la pesanteur au dessus d'un miroir parfait voient leur énergie restreinte à prendre des valeurs discrètes. Le projet GRANIT vise a mesurer précisément les niveaux d'énergie. Une méthode originale de mesure de l'énergie de transition entre deux états quantiques est proposée, ce sera la première phase du projet GRANIT. Sa faisabilité est démontrée et les paramètres du dispositifs sont optimises. La sensibilité de GRANIT à une hypothétique interaction supplémentaire entre le neutron et le miroir est analysée. Le potentiel de découverte est compare à celui d'autres expériences utilisant des neutrons. Notamment, l'utilisation d'un spectrometre dédié à la mesure du moment dipolaire électrique du neutron pour rechercher une nouvelle interaction dépendant du spin sera discutée.

Neutrino oscillations, the baryon asymmetry and dark matter are important evidences of new physics beyond the Standard Model. Neutrino oscillations imply neutrino masses and a lepton mixing matrix that can contribute to flavour violating processes and CP violation at low energies, accessible to next experiments, and to the CP violation necessary for baryogenesis. Among the most interesting implications, is flavour violation in the lepton sector, but it has only been observed in neutrino oscillations. By analogy with quarks, it is then possible to deduce a principle of minimal flavour violation for leptons. Since such formulation is not straightforward in the lepton sector, we discuss dierent possibilities. Then we propose a definition which could be applied to various models and could help us in selecting between the possible neutrino mass generating mechanisms. Furthermore, if the seesaw mechanism describes neutrino masses, we can have a natural explanation to the baryon asymmetry of the universe with leptogenesis. In the context of leptogenesis including flavour effects, we demonstrate that the baryon asymmetry of the universe is insensitive to the low energy CP violating phases. This study is performed in the minimal extension of the Standard Model, with the introduction of 3 right-handed neutrinos and type-1 seesaw, only, and it is extended, in a following study, to the supersymmetric case. Since the seesaw parameter space is quite large, the numerical study is developed with the Markov Chain Monte Carlo method. In relation to dark matter, we study a scenario with very weakly coupled candidates and their production through the decay of a charged long-lived scalar particle. We compute the scalar particle number density, evaluating its gauge interactions, and compare it with Big-Bang Nucleosynthesis bounds. Then, we apply our results to the Minimal Supersymmetric Standard Model scenario with axino or gravitino as Lightest Supersymmetric Particle and stau or stop as Next to Lightest Supersymmetric Particle.

Le premier chapitre contient un bref rappel sur la physique des saveurs lourdes dans le Modèle Standard, et conclut par une description succinte de l'approche statistique utilisée dans CKMfitter.<br /> Le chapitre suivant évoque la violation de CP dans le secteur des kaons : sont traitées les contraintes sur la matrice CKM provenant des mesures de εK, ε′/ε, ainsi que l'´état des lieux et les perspectives sur la recherche des modes rares K+→π+νν et<br />KL→π0νν ; ce chapitre conclut par une étude prospective pour estimer le potentiel de<br />physique des kaons dans le cadre du modèle CKM. <br />Suivent deux chapitres décrivant des analyses de physique dans l'expérience BaBar : est d'abord présentée en détail l'analyse en amplitudes du mode B0 → K+π−π0 ; suit un état des lieux plus succint sur l'analyse en amplitudes dépendantes du temps du mode<br />B0 → K0π+π−, qui a déj`a fourni des résultats préliminaires à l'été 2007. La discussion est ensuite complétée par une description qualitative sur un projet d'étude combinée des contraintes sur la matrice CKM provenant des modes B → Kππ.

pas de résumé

Cette thèse a comme but la préparation à la recherche du boson de Higgs dans le canal diphoton au LHC, avec le détecteur ATLAS. <br /><br />Les problématiques qui sont étudiées s'articulent autour de la reconstruction du vertex H en deux photons, avec l'aide du calorimètre électromagnétique et du détecteur interne, et de la résolution en masse invariante diphoton.<br /><br />Des simulations différentes du détecteur ATLAS et les effets de la quantité de matière et des désalignements ont été étudiés. Des problématiques de calcul de la signification statistique ont également été discutées et le potentiel de découverte pour une basse luminosité integrée a été évalué.<br /><br />Une partie de la thèse se place dans le cadre des données CSC qui utilisent la plus récente simulation du détecteur ainsi que des méthodes de reconstruction mises au point et qui servent à effectuer une mise à jour de l'analyse effectuée par ATLAS. Toutes les étapes du traîtement du signal et du bruit de fond ont été discutées. Finalement on s'attend à voir un signal de 3 sigma avec une luminosité integrée de 10 fb-1