O objetivo deste trabalho é calcular a ação de teoria de campos de supercordas para os dois primeiros níveis de massa da supercorda, incluindo os dois setores de projeção GSO. Considerando uma corda tipo II-A na presença de uma D9-brana instável, calcula-se a ação para o táquion, o campo de gauge e os férmions GSO(+) e GSO(-). O trabalho é realizado usando o formalismo híbrido e usando-se a ação de campos de supercordas de Berkovits, que inclui o setor Ramond. Para tanto, inclui-se amplo material de revisão sobre teorias e teorias de campos de supercordas. A construção de operadores de vértice GSO(-) no formalismo híbrido é feita em detalhes. Considerações sobre a ação obtida e perspectivas futuras do trabalho são discutidas no final. / The goal of this work is to compute the superstring field theory action contribution for the two first mass level of the superstring, including both GSO sectors. A type IIA superstring in the presence of an unstable non-BPS D9 brane is considered and the computation of the action for the Tachyon, Gauge Field and Massless fermions from GSO(+) and GSO(-) sectors is done. The main work is accomplished using the hybrid formalism and the superstring field theory action of Berkovits, including the Ramond Sector. This task is accomplished by including revision material thoroughly, for conformal and super conformal field theory. Construction of physical GSO(-) vertex operators is considered in detail. At the end, theres a discussion about the action for these fields and some future perspectives are considered.

Estimar de forma realista o alcance de descoberta de um experimento de colisão de altas energias, como o realizado no Large Hadron Collider (LHC) do CERN, é uma tarefa complexa, principalmente em vista das técnicas de simulação de eventos e dos métodos de estatística multivariada utilizadas pelas colaborações experimentais na comparação dos dados com as predições teóricas. Descobrir uma nova partícula, contudo, é apenas o primeiro passo na investigação experimental. De modo a estabelecer qual dos eventuais modelos teóricos concorrentes é favorecido pelos dados, torna-se imprescindível o estudo das propriedades desta nova partícula e de suas interações com o restante do espectro. Informações como os números quânticos de spin, conjugação de carga ($C$) e paridade ($P$), podem ser obtidas através do estudo das correlações entre os momentos das partículas produzidas codificadas nas distribuições cinemáticas. O discernimento entre os vários modelos, portanto, passa a ser um problema de combinar todas estas informações de forma eficiente e compará-las aos dados experimentais através de um teste estatístico e decidindo, assim, pela confirmação ou não de um novo sinal e sobre o modelo que melhor explica aqueles dados. No trabalho realizado nesta tese, investigamos o limite do LHC, operando a uma energia de centro-de-massa de 14 TeV, para a descoberta de um modelo supersimétrico (SUSY) simplificado e de seu discernimento em relação a um modelo de dimensões extras universais mínimas (MUED), usando eventos de produção de novas partículas coloridas decaindo, através de cadeias curtas, em jatos e missing energy. Nossa abordagem avança em diversos aspectos em comparação a fenomenologias mais simplificadas: utilizando uma análise estatística multivariada, levando em conta incertezas sistemáticas nas normalizações das seções de choque e no formato das distribuições, empregando técnicas de identificação de jatos de quarks e glúons para uma melhor separação dos backgrounds do Modelo padrão (MP), escaneando e otimizando os cortes retangulares, simulando eventos de forma cuidadosa e com correções de ordem superior da cromodinâmica quântica (QCD). Eventos de SUSY e MUED foram simulados para 150 diferentes espectros de massa, ainda não excluídos pelo LHC, e estimamos o potencial de descoberta e de discernimento SUSY versus MUED no plano de massas de squarks e gluinos utilizando as técnicas acima mencionadas. Mostramos, em primeiro lugar, que mesmo de forma simplificada, inserir incertezas sistemáticas é essencial para uma estimativa mais realista do potencial do acelerador, principalmente no que diz respeito ao aumento de luminosidade integrada. Para incertezas nas normalizações da ordem de 20%, o ganho no potencial de busca torna-se mais limitado. Por exemplo, passando de 100 a 3000 fb$^{-1}$, o alcance na massa dos squarks aumenta de 2.8 para ~ 3.1$ TeV, ao passo que, sem levar em conta estas incertezas, a estimativa é mais otimista, indo de 3.0 a ~ 3.5 TeV para as mesmas luminosidades. Performance similar é observada no discernimento SUSY versus MUED, onde é possível obter uma significância de $5\\sigma$ para massas de squarks de até ~ 2.7 TeV e gluinos ~ 5 TeV, mantendo-se as incertezas sistemáticas a um nível menor do que 10% aproximadamente. De forma geral, concluímos que um modelo supersimétrico simplificado, como o estudado aqui, pode ser descoberto e confirmado (em relação a um dos seus mais populares concorrentes, MUED) para um espectro com squarks, gluinos e neutralinos de aproximadamente 2.5, 5.0 e 0.3 TeV, respectivamente, se as incertezas sistemáticas puderem ser controladas a um nível de 10 % ou menos, após 3 ab$^{-1}$ de luminosidade integrada. / The problem of estimating, in a realistic way, the reach of an experiment in high energy physics, such as the CERN Large Hadron Collider (LHC), is a difficult task. Specially due to the simulations techniques and the multivariate statistics for data and theory comparisons, used by experimental collaborations. The discovery of a new particle is just the first step in the experimental exploration. The properties of this particle, like parity, spin and charge are conditions to assert which physics model is favored by the collected data. It is possible to measure these properties with the analyses of the particle momentum correlations through the kinematical distributions. The discriminations among different models turns into a problem of combining all this informations, in a efficient way, and compare with experimental data through a statistical test, and choosing for the confirmation or exclusion of a signal and which model best describes the data. In this work, we investigate the limits of the LHC, working in a center of mass energy of 14 TeV, for the discovery of a simplified model of supersymmetry (SUSY) and the discrimination with a model of minimal universal extra dimensions (MUED), using productions of heavy colored particles decaying, through short decays chains, in jets and missing energy. Our approach progresses in different aspects compared with simplified phenomenological analyses: we used a multivariate statistical analysis, considered systematical uncertainties in the rate and shape of distributions, implemented techniques of quarks and gluons jet tagging identification for a good separation between signal and backgrounds, scanning for the best rectangular cuts and simulating events in a careful way with 1-loop corrections from quantum chromodynamics. Our events were simulated for 150 different mass spectrums, not excluded by the LHC, and we estimate the potencial for discovery and discrimination of SUSY versus MUED in a squarks-gluinos mass plane, using the techniques mentioned above. We proved, in first place, that even in a simplified way, inserting systematical uncertainties it\'s essential for an estimative more realistic of the collider\'s reach, mainly with the increasing of integrated luminosity. For systematical rate uncertainties in the distribution of 20%, the gain in the discovery potencial is very limited. For example, increasing from 100 to 3000 fb$^{-1}$, the reach in the squark mass increase from ~ 2.8 to 3.1 TeV. On the other hand, without systematical uncertainties in rate distributions, the reach is more optimistic, from 3.0 TeV to ~ 3.5 TeV, for the same luminosities. Similar performance was observed in the discrimination of Susy versus MUED, where it\'s possible to obtain significance of $5\\sigma$ for squark masses up to ~ 2.7$ TeV and gluinos of ~ 5 TeV, keeping systematical uncertainties at a level about 10%. In general, we conclude that a supersymmetryc model, like we studied here, can be discovered and confirmed (compared to one of its more popular competitors, MUED) for a mass spectrum of squarks, gluinos and neutalinos about 2.5, 5.0 and 0.3 TeV, respectively, if it\'s possible to control the systematical uncertainties at a level about 10%, after 3 ab$^{-1}$ of integrated luminosity.

Nesta tese foram estudadas configurações de cordas em movimentos de rotação e de oscilação no âmbito da correspondência AdS/CFT. Estas cordas movimentam-se nos espaços AdS5 × S5, de Lunin e Maldacena, R1, 9 e R1, 9 deformado. Para o caso da corda em rotação, determinou-se a existência do mágnon gigante e da corda farpada. Para o caso da corda oscilante, foram encontradas as soluções das equações de movimento clássicas e determinada a energia. Também calculamos explicitamente o número de supercargas preservadas para os espaços AdS5 × S5 e para R1, 9 deformado. / In this thesis we studied rotating and oscillating strings under the AdS/CFT correspondence. These strings move in the AdS5 × S5, Lunin and Maldacena, R1, 9 and deformed R1, 9 spaces. In the case of the rotating string, the giant magnon and the spiky string were determined. In the case of the oscillating string, we found the solutions fo the classical equations of motion and the energy. We also explicitly calculated the number of preserved supercharges for the AdS5 × S5and deformed R1, 9 spaces.

Através do formalismo de supercampos, estudamos as propriedades ultravioletas da eletrodinâmica quântica supersimétrica no espaço-tempo tridimensional. Mostramos que esta teoria é finita em todas as ordens de perturbação num calibre particular. Também apresentamos uma análise perturbativa do modelo de Chern-Simons supersimétrico acoplado a um supercampo escalar complexo. Com isso, estudamos a quebra da simetria de calibre U(1) e calculamos as primeiras correções quânticas à ação efetiva na fase quebrada. Mostramos que a renormalização da equação de gap é suficiente para assegurar a renormalizabilidade do modelo em um laço de aproximação. Nós também verificamos que quando acoplado a um supercampo escalar sem massa, o modelo de Chern-Simons supersimétrico apresenta geração dinâmica de massa, um mecanismo que em D = 2 + 1 dimensões do espaço-tempo, diferentemente do modelo não-supersimétrico quadridimensional (Coleman- Weinberg), só ocorre a partir da aproximação de dois laços. Alguns outros resultados relacionados são também incluídos nesta tese, tais como um estudo do modelo CP**(N-1) não-comutativo supersimétrico e a equivalência entre os modelos de Maxwell-Chern-Simons e Auto-Dual supersimétricos. Em todo nosso trabalho, supersimetria é manifesta. / Within the superfield formalism, we study the ultraviolet properties of the three-dimensional supersymmetric quantum electrodynamics. The theory is shown to be finite at all loops orders in a particular gauge. We also present a perturbative analysis of the supersymmetric Chern-Simons model coupled to a Higgs field. We study the spontaneous symmetry breaking of the U(1) gauge symmetry and evaluate the first quantum corrections to the effective action in the broken phase. We show that the infinite renormalization of the gap equation is enough to ensure the renormalizability of the model at the first loop level. We also verify that when coupled to a massless scalar superfield, the supersymmetric Chern-Simons model present dynamical generation of mass, a mechanism that in D = 2 + 1 spacetime dimensions, differently from the four-dimensional non-supersymetric model (Coleman-Weinberg), only occurs from two-loop order. Some other related results are also enclosed in this thesis, such as a study of the supersymmetric noncommutative CP**(N-1) model and the equivalence between Maxwell-Chern-Simons and Self-Dual supersymmetric models. In whole work, supersymmetry is manifest.

Le Modèle Standard de la physique des particules a été remarquablement testé auprès des grands accélérateurs jusqu'à une énergie de l'ordre du TeV. Malgré ses succès, un grand nombre de problèmes restent sans solution. Par exemple, le Modèle Standard ne permet pas d'expliquer l'origine de la prépondérance de la matière sur l'antimatière, ni l'origine du rapport 1016 entre l'échelle de brisure électrofaible et l'échelle de Planck. Les interactions électrofaibles et fortes ne sont pas unifiées et de plus, la gravité est absente. Cette thèse s'interesse à différents aspects phénoménologiques des théories d'extension du Modèle Standard. La première partie porte sur la baryogénèse électro- faible dans le Modèle Standard Supersymétrique Minimal et plus spécifiquement sur la dynamique de la transition de phase électrofaible. La deuxième partie est consacrée au problème de la brisure spontanée de la supergravité dans les théories de cordes effectives, les seules théories offrant l'espoir d'une description unifiée des interactions gravitationnelles avec les autres forces fondamentales. Enfin, la dernière partie discute un certain nombre de modèles phénoménologiques utilisant les propriétés des branes et la présence de dimensions supplémentaires afin de reformuler le problème de hiérarchie de jauge en termes géométriques.

While the dark matter has so far only revealed itself through the gravitational influence it exerts on its surroundings, there are good reasons to believe it is made up by WIMPs – a hypothetical class of heavy elementary particles not encompassed by the Standard Model of particle physics. The Inert Doublet Model constitutes a simple extension of the Standard Model Higgs sector. The model provides a new set of scalar particles, denoted inert scalars because of their lack of direct coupling to matter, of which the lightest is a WIMP dark matter candidate. Another popular Standard Model extension is that of supersymmetry. In the most minimal scenario the particle content is roughly doubled, and the lightest of the new supersymmetric particles, which typically is a neutralino, is a WIMP dark matter candidate. In this thesis the phenomenology of inert scalar and supersymmetric dark matter is studied. Relic density calculations are performed, and experimental signatures in indirect detection experiments and accelerator searches are derived. The Inert Doublet Model shows promising prospects for indirect detection of dark matter annihilations into monochromatic photons. It is also constrained by the old LEP II accelerator data. Some phenomenological differences between the Minimal Supersymmetric Standard Model and a slight extension, the Beyond the Minimal Supersymmetric Standard Model, can be found. Also, supersymmetric dark matter models can be detected already within the early LHC accelerator data.

For more than 30 years the Standard Model has been the theoretical foundation for particle physics. The theory has been verified successfully by experimental tests. Its biggest shortcoming is the non-discovery of the Higgs boson,responsible for giving the other particles masses. Despite its success there are hints that the Standard Model is not the complete theory and many extensions of it, such as supersymmetry, have been proposed. Extended theories often predict the existence of a charged Higgs boson and its detection will be a clear sign of physics beyond the Standard Model. The main focus in this thesis is on various phenomenological aspects of the charged Higgs boson. For favorable mass and couplings direct detection is shown to be possible at the Large Hadron Collider in production with an associated W boson. It is also shown how a light charged Higgs can have measurable effects on spin correlations in decays of pair-produced top quarks. The charged Higgs boson can also be seen indirectly, in for example B-meson decays, which can be used to put constraints on its mass and fermion couplings. Exclusion limits in two supersymmetric models are given together with a comparison with the discovery potentials for the LHC experiments. A tool for calculating properties, such as masses and decays, of both charged and neutral Higgs bosons in the Two-Higgs-Doublet Model is also presented. B-meson decays can also be used to test aspects of the strong interaction. Part of this thesis deals with improving and applying phenomenological models to B-meson decays. Although these models are not derived from first principles, their success shows that they capture important features of non-perturbative strong interactions.

Non-linear sigma models with extended supersymmetry have constrained target space geometries, and can serve as effective tools for investigating and constructing new geometries. Analyzing the geometrical and topological properties of sigma models is necessary to understand the underlying structures of string theory. The most general two-dimensional sigma model with manifest N=(2,2) supersymmetry can be parametrized by chiral, twisted chiral and semichiral superfields. In the research presented in this thesis, N=(4,4) (twisted) supersymmetry is constructed for a semichiral sigma model. It is found that the model can only have additional supersymmetry off-shell if the target space has a dimension larger than four. For four-dimensional target manifolds, supersymmetry can be introduced on-shell, leading to a hyperkähler manifold, or pseudo-supersymmetry can be imposed off-shell, implying a target space which is neutral hyperkähler. Different sigma models and corresponding geometries can be related to each other by T-duality, obtained by gauging isometries of the Lagrangian. The semichiral vector multiplet and the large vector multiplet are needed for gauging isometries mixing semichiral superfields, and chiral and twisted chiral superfields, respectively. We find transformations that close off-shell to a N=(4,4) supersymmetry on the field strengths and gauge potentials of the semichiral vector multiplet, and show that this is not possible for the large vector multiplet. A sigma model parametrized by chiral and twisted chiral superfields can be related to a semichiral sigma model by T-duality. The N=(4,4) supersymmetry transformations of the former model are linear and close off-shell, whereas those of the latter are non-linear and close only on-shell. We show that this discrepancy can be understood from T-duality, and find the origin of the non-linear terms in the transformations.

We describe a procedure for classifying 4D N=2 superconformal theories of the type introduced by Davide Gaiotto. Any punctured curve, C, on which the 6D (2,0) SCFT is compactified, may be decomposed into 3-punctured spheres, connected by cylinders. The 4D theories, which arise, can be characterized by listing the ``matter" theories corresponding to 3-punctured spheres, the simple gauge group factors, corresponding to cylinders, and the rules for connecting these ingredients together. Different pants decompositions of C correspond to different S-duality frames for the same underlying family of 4D \mathcal{N}=2 SCFTs. We developed such a classification for the A_{N-1} and the D_N series of 6D (2,0) theories. We outline the procedure for general A_{N-1} and D_N, and construct, in detail, the classification through A_4 and D_4, respectively. / text

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