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We investigate several aspects of four dimensional supersymmetric gauge theories with the minimal amount of supercharges both from the theoretical and the phenomenological view point. On the theoretical side we investigate the behavior of two-point correlators of short multiplets for vacua that spontaneously break supersymmetry. The main goal is to build up an exhaustive description of the supersymmetry breaking dynamics that it is easily extendable to strongly coupled gauge theories. When strong coupling is involved we study the behavior of two-point correlators by means of AdS/CFT techniques building up models of strongly coupled hidden sectors that break supersymmetry and can be described holographically by gauged supegravity in five dimensions. These hidden sectors have also some phenomenological interest in particle physics beyond the Standard Model since they can be used as supersymmetry-breaking sectors in models where the breaking of supersymmetry is mediated by gauge interactions. On the more phenomenological side we study how the Higgs mass requirements constraints gauge mediation models and what could be possible interesting signatures of these scenarios at LHC. / Doctorat en sciences, Spécialisation physique / info:eu-repo/semantics/nonPublished

Le modèle standard supersymétrique minimal (MSSM) est probablement une des théories de nouvelle physique les plus étudiées. Dans la plupart des études phénoménologiques, on fait l'hypothèse de la violation minimale de la saveur dans laquelle toutes les interactions violant la saveur sont directement liées à la matrice CKM du modèle Standard. Cependant, si la supersymétrie est plongée dans des cadres plus larges tels que les théories dites de Grande Unification, de nouvelles sources de violation de la saveur peuvent apparaitre. Les termes correspondant dans le lagrangien sont directement liés au choix du mécanisme de brisure de la supersymétrie. Or, à l'heure actuelle, aucun consensus n’existe quant au choix exact du mécanisme de brisure de la SUSY. Plusieurs mécanismes ont été évoqués récemment (entre autre, par le co-directeur de la thèse), qui pourraient conduire à des signatures prometteuses au LHC pour différents scénarios et domaines de paramètre. Le projet est donc idéalement situé à la frontière entre le 'model building' et des aspects plus phénoménologiques. Pour cette raison, le thésard sera naturellement amené à interagir de manière active avec le groupe de phénoménologie de physique des particules du LAPTh ainsi qu'avec les groupes de physique des particules du LAPP (ATLAS, LHCb..), laboratoire expérimental partageant le même bâtiment que le LAPTh. De plus, des collaborations sur le plan national, en particulier avec le LPSC de Grenoble, ainsi que sur le plan international, avec les universités de Würzburg et Münster (Allemagne) et le nouvel institut de physique de NATAL (Brésil) sont également envisagées. / The Minimal Supersymmetric Standard Model (MSSM) is probably the best studied of all new physics theories. In most phenomenological studies, one assumes the hypothesis of minimal flavour violation, where all flavour-violating interactions are related to the CKM-matrix (as it is the case in the standard model). However, if supersymmetry is embedded in larger frameworks such as grand unified theories (GUT), new sources of flavour violation can appear. The corresponding terms in the Lagrangian are directly related to the mechanism of supersymmetry breaking, for which at present no theoretical consensus exists. Several processes have recently been evoked (among others by the co-director of the proposed thesis), which might lead to promising signatures at the LHC if non-minimal flavour violation is realized. These studies, however, included flavour-violating terms directly at the electroweak scale without taking into account their possible origin at some high scale. The main goal of the project is to extend the previous work in order to take into account the link between the electroweak and the GUT scale. This will allow to put constraints on parameters describing supersymmetry breaking using constraints imposed at the electroweak scale. A second goal is the analysis of relevant processes with the help of current Monte-Carlo simulation tools in order to study the background and thus clarify the observability at LHC for different scenarios and regions of parameters space. So, the project is ideally situated at the frontier between model building and more phenomenological aspects. For this reason the project naturally includes interactions with the local particle physics phenomenology group at LAPTh as well as with the the neighbouring experimental groups (e.g. ATLAS, LHCb) at LAPP. Moreover, collaborations on the national, in particular with the LPSC Grenoble, and international level, e.g. with the University of Würzburg (Germany), the University of Münster (Germany) and the newly created International Institute of Physics in Natal (Brasil) are envisaged.

This thesis is devoted to the study of orientifolds and dynamical supersymmetry breaking in configurations of D-branes on toric Calabi-Yau singularities, through the lens of dimer models. We first review the basic ingredients of string theory that led to the formulation of gauge/gravity dualities in terms of dimers. Then, we discuss the non-abelian anomaly cancellation conditions for the supersymmetric gauge theories arising on D-branes and provide necessary geometric criteria to determine whether an orientifold projection can be safely introduced. We also find a new realization of orientifold projection without fixed loci in dimer models and expand on its physical features. We argue that it exhausts the possibilities of orientifolding dimer models. In the subsequent part of the thesis, we investigate dynamical supersymmetry breaking vacua in the same class of models and their typical instability along N=2 Coulomb branches. This leads us to formulate a no-go theorem against their stability based on geometrical features of the singularity, and then to establish a precise way to circumvent it. We eventually find the first instance of stable dynamical supersymmetry breaking vacuum in string theory from D-branes on a toric Calabi-Yau singularity, the Octagon. / Doctorat en Sciences / info:eu-repo/semantics/nonPublished

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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.

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In this thesis we employ string perturbation theory in toroidal orbifold models to study aspects of supersymmetry breaking in type IIB string theory. First, we determine the dependence of physical Yukawa couplings on blow-up moduli in models with D3-branes at orbifold singularities. Blow-up moduli are scalar fields describing the size of small blow-up cycles in the compactification geometry. In models implementing moduli stabilisation these fields can acquire F-terms and break supersymmetry. We examine the moduli-dependence of physical Yukawa couplings at string tree-level by computing disk correlation functions involving a Yukawa interaction of visible sector fields and an arbitrary number of blow-up moduli. We perform the calculation for one blow-up insertion explicitly and find that the correlation function vanishes if the blow-up modulus is associated with a small cycle distant to the visible sector. For more than one blow-up insertion we show that all such correlation functions are exponentially suppressed by the compactification volume. We explain how these results are relevant to suppressing soft terms to scales parametrically below the gravitino mass. Further, we determine corrections to holomorphic Yukawa couplings on D3-branes at an orbifold singularity due to non-perturbative effects such as gaugino condensation on a stack of D7-branes. This can be done by calculating a one-loop threshold correction to the gauge coupling on the D7-branes. We show that, if present, the new contributions to Yukawa couplings are not aligned with the tree-level couplings. As the new Yukawa couplings contribute to soft A-terms they are sources of flavour-changing neutral currents. Last we discuss an effect unrelated to supersymmetry breaking. We show that orbifold models with D3-branes at orbifold singularities can exhibit kinetic mixing of different massless Abelian factors. For this to be possible, the relevant U(1) factors have to be associated with more than one orbifold singularity.

Bien que l'on ne sache pas (encore) quel phénomène unitarise la diffusion WLWL à l'échelle du TeV, les données indirecte actuelles favorise le boson de Higgs. Etant donné que cette particule scalaire pourrait être aussi lourde que la masse de Planck, comment peut-on expliquer sa légèreté ? La supersymmétrie (SUSY), brisée à l'échelle du TeV, peut effectuer cette stabilisation, et permettre du même coup l'existence de Théories de Grande Unifications (GUTs). Ces SUSY GUTs réalisées dans une dimension supplémentaire compactifiée, peuvent être particulièrement simples. De plus, elles peuvent être prises comme limite basse énergie d'une théorie de cordes. Cette thèse est consacrée à l'étude de tels modèles de SUSY GUTs. Nous avons étudié, développé et étendu certains aspects de la classe de modèle d'Unification Jauge-Higgs, et de la classe de modèle d'Unification Holographique. Différents aspects de la physique basse-énergie ont été étudiés, incluant spectre de masses, physique des saveur, matière noire, et phénoménologie au LHC. / Although one does not know (yet) which phenomenon unitarizes WLWL scattering at the TeV scale, indirect data currently favors the Higgs boson. Since such a scalar particle is susceptible to become as heavy as the Planck mass, how can one explain its lightness ? Supersymmetry (SUSY), broken at the TeV scale, can do this stabilization, providing in the same time models of Grand Uni fied Theories (GUTs). These SUSY GUTs, combined with extra spatial dimensions compacti fied on an interval, can be particularly simple. Moreover they can be seen as the low energy limit of some string theory. This thesis is devoted to the study of such models of SUSY GUTs on flat and warped orbifolds, trying to cover the range from models to experimental constraints. We studied, developed and extended certain aspects of two interesting frameworks of this type: a framework with gauge-Higgs uni fication, and the framework of holographic grand uni fication. We investigated several aspects of the low-energy implications, including mass spectra, flavour constraints, dark matter and LHC phenomenology