A light neutralino in hybrid models of supersymmetry breaking

We show that in gauge mediation models where heavy messenger masses are provided by the adjoint Higgs field of an underlying SU(5) theory, a generalized gauge mediation spectrum arises with the characteristic feature of having a neutralino LSP much lighter than in the standard gauge or gravity mediation schemes. This naturally fits in a hybrid scenario where gravity mediation, while subdominant with respect to gauge mediation, provides mu and Bmu parameters of the appropriate size for electroweak symmetry breaking.Comment: 32 pages. v2: revised discussions of the generation of Bmu and of the dark matter constraint; numerous small redactional changes; remarks and references adde

Développer le goût des mathématiques en s’appuyant sur la diversité des étudiants

Comprend des références bibliographiquesComment gérer l’hétérogénéité d’une classe de mathématiques en aidant les étudiants à développer leur plaisir au travail ? Parce que nous accueillons au sein d’une même classe des bacheliers généraux et technologiques aux niveaux très variés, nous avons mis en place une série de méthodes pédagogiques qui permettent de respecter l’altérité des apprenants tout en restant dans un cadre formel éducatif. Nous présentons ici l’ensemble de méthodes utilisées ainsi que leur impact sur la motivation et le plaisir des étudiants lors du cours de mathématiques du premier semestre (S1) de première année de licence (L1) à l’Institut Villebon - Georges Charpak

A light neutralino in hybrid models of supersymmetry breaking

We show that in gauge mediation models where heavy messenger masses are provided by the adjoint Higgs field of an underlying SU(5) theory, a generalized gauge mediation spectrum arises with the characteristic feature of having a neutralino LSP much lighter than in the standard gauge or gravity mediation schemes. This naturally fits in a hybrid scenario where gravity mediation, while subdominant with respect to gauge mediation, provides mu and Bmu parameters of the appropriate size for electroweak symmetry breaking.Comment: 32 pages. v2: revised discussions of the generation of Bmu and of the dark matter constraint; numerous small redactional changes; remarks and references adde

Detecting fatigue of sport horses with biomechanical gait features using inertial sensors

Detection of fatigue helps prevent injuries and optimize the performance of horses. Previous studies tried to determine fatigue using physiological parameters. However, measuring the physiological parameters, e.g., plasma lactate, is invasive and can be affected by different factors. In addition, the measurement cannot be done automatically and requires a veterinarian for sample collection. This study investigated the possibility of detecting fatigue non-invasively using a minimum number of body-mounted inertial sensors. Using the inertial sensors, sixty sport horses were measured during walk and trot before and after high and low-intensity exercises. Then, biomechanical features were extracted from the output signals. A number of features were assigned as important fatigue indicators using neighborhood component analysis. Based on the fatigue indicators, machine learning models were developed for classifying strides to non-fatigue and fatigue. As an outcome, this study confirmed that biomechanical features can indicate fatigue in horses, such as stance duration, swing duration, and limb range of motion. The fatigue classification model resulted in high accuracy during both walk and trot. In conclusion, fatigue can be detected during exercise by using the output of body-mounted inertial sensors

Flavour in supersymmetry: horizontal symmetries or wave function renormalisation

We compare theoretical and experimental predictions of two main classes of models addressing fermion mass hierarchies and flavour changing neutral currents (FCNC) effects in supersymmetry: Froggatt-Nielsen (FN) U(1) gauged flavour models and Nelson-Strassler/extra dimensional models with hierarchical wave functions for the families. We show that whereas the two lead to identical predictions in the fermion mass matrices, the second class generates a stronger suppression of FCNC effects. We prove that, whereas at first sight the FN setup is more constrained due to anomaly cancelation conditions, imposing unification of gauge couplings in the second setup generates conditions which precisely match the mixed anomaly constraints in the FN setup. Finally, we provide an economical extra dimensional realisation of the hierarchical wave functions scenario in which the leptonic FCNC can be efficiently suppressed due to the strong coupling (CFT) origin of the electron mass.Comment: 23 page

Aspects phénoménologiques de la brisure de supersymétrie

Le sujet ne colle pas mais les autres propositions sont encore plus éloignées de mon sujet de thèse !In this thesis, we study some of the consequences of supersymmetry breaking and its mediation at low energy. First we focused on models in which supersymmetry is mediated through messengers. We succeed in building a model that was both stable and had a non-hierarchical spectrum. We also studied the coupling between messengers and grand unification fields, finding atypical spectra with light neutralino or gluino. Supersymmetry was also a way to address the hierarchy problem in the standard model, and we compared two types of models, one using horizontal gauge symmetries and the other using wave functions in extra-dimensionnal models. Finally, we worked on constrained superfields in order to develop a formalism for non-linear supersymmetry.Dans cette thèse, nous étudions certaines des conséquences liées à la brisure de supersymétrie et à sa transmission à basse énergie. Nous nous sommes concentrés sur les modèles où la brisure de supersymétrie est transmise par l'intermédiaire de messagers. Nous avons réussi à construire un modèle à la fois stable et présentant un spectre non-hiérarchique de particules supersymétriques. Nous avons aussi étudié le couplage des messagers au secteur de grande unification, aboutissant à des spectres atypiques dans le cas de la médiation de jauge, comme celui possédant un neutralino ou un gluino plus léger que le reste du spectre (respectivement LSP et NLSP). Nous avons également comparé deux modèles autour du problème de hiérarchie dans le Modèle Standard, l'un utilisant des symétries de jauge horizontales et l'autre des fonctions d'onde hiérarchiques avec dimension supplémentaire. Enfin, nous avons réfléchi à la facon d'utiliser des superchamps contraints pour travailler sur des modèles où la supersymétrie est réalisée de manière non linéair

On messengers and metastability in gauge mediation

18 pagesOne notoriously difficult problem in perturbative gauge mediation of supersymmetry breaking via messenger fields is the generic presence of a phenomenologically unacceptable vacuum with messenger vevs, with a lower energy than the desired (MSSM) vacuum. We investigate the possibility that quantum corrections promote the latter to the ground state of the theory, and find that this is indeed feasible. For this to happen, the couplings of the messengers to the goldstino superfield must be small, and this implies an additional suppression of the MSSM soft terms with respect to the supersymmetry breaking scale. This in turns sets a lower limit on the masses of the messengers and of the supersymmetry breaking fields, which makes both sectors inaccessible at colliders. Contrary to other scenarios like direct gauge mediation, gaugino masses are unsuppressed with respect to scalar masses

A light neutralino in hybrid models of supersymmetry breaking

29 pagesWe show that in gauge mediation models where heavy messenger masses are provided by the adjoint Higgs field of an underlying SU(5) theory, a generalized gauge mediation spectrum arises with the characteristic feature of having a neutralino much lighter than in the standard gauge or gravity mediation schemes. This naturally fits in a hybrid scenario where gravity mediation, while subdominant with respect to gauge mediation, provides mu and B mu parameters in the TeV range

Detecting fatigue of sport horses with biomechanical gait features using inertial sensors.

Detection of fatigue helps prevent injuries and optimize the performance of horses. Previous studies tried to determine fatigue using physiological parameters. However, measuring the physiological parameters, e.g., plasma lactate, is invasive and can be affected by different factors. In addition, the measurement cannot be done automatically and requires a veterinarian for sample collection. This study investigated the possibility of detecting fatigue non-invasively using a minimum number of body-mounted inertial sensors. Using the inertial sensors, sixty sport horses were measured during walk and trot before and after high and low-intensity exercises. Then, biomechanical features were extracted from the output signals. A number of features were assigned as important fatigue indicators using neighborhood component analysis. Based on the fatigue indicators, machine learning models were developed for classifying strides to non-fatigue and fatigue. As an outcome, this study confirmed that biomechanical features can indicate fatigue in horses, such as stance duration, swing duration, and limb range of motion. The fatigue classification model resulted in high accuracy during both walk and trot. In conclusion, fatigue can be detected during exercise by using the output of body-mounted inertial sensors

Valoriser travail collaboratif et créativité dès la licence : La démarche scientifique en action

International audienceWe describe here the succession of scientific projects proposed all along our 3 year-bachelor teaching program to the students of Villebon - Georges Charpak Institute, with the aim of forming scientists with novel and diverse profiles. Innovative pedagogy and collaborative projects are used from the very beginning of the 1st year in order to develop creativity and appetite for sciences. Creativity should then stimulate pleasure for learning basics.Nous décrivons ici comment nous avons articulé une série de projets scientifiques en 1ère et 2ème années de Licence « Sciences et Technologie » de l'Institut Villebon-Georges Charpak pour amener progressivement les étudiants à coopérer et à développer leur créativité scientifique. Cette construction est utilisée pour servir de socle à une reprise de confiance en soi de la part d'étudiants pouvant présenter initialement des fragilités scolaires. La créativité n'intervient donc pas après avoir consolidé les savoirs de base mais, au contraire, comme stimulant pour ouvrir l'appétit d'apprendre