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Mesure de la masse et de la largeur du boson de Higgs se désintégrant en 4 leptons via ZZ* et reconstruction des électrons dans l’expérience CMS auprès du LHC.
No full textThis thesis document reports measurements of the mass and width of the new boson re- cently discovered at the Large Hadron Collider (LHC), candidating to be the Standard Model Higgs boson. The analysis uses proton-proton collision data recorded by the Compact Muon Solenoid (CMS) detector at the LHC, corresponding to integrated luminosities of 5.1 fb−1 at 7 TeV center of mass energy and 19.7 fb−1 at 8 TeV center of mass energy. Set of events selecting Higgs boson via the H → Z Z decay channel, where both Z bosons decay to electron or muon lepton pairs, is used for the Higgs boson properties measurements. A precise measurement of its mass has been performed and gives 125.6 ± 0.4(stat) ± 0.2 (syst) GeV. Constraints on the Higgs boson width were established using its off-shell production and decay to a pair of Z bosons, where one Z boson decays to an electron or muon pair, and the other to an electron, muon, or neutrino pair. The obtained result is an upper limit on the Higgs boson width of 22 MeV at a 95% confidence level, which is 5.4 times the expected value in the standard model at the measured mass. Throughout the thesis, a particular attention has been put on the elec- tron momentum estimation. The combination of the momentum estimate with the tracker and the energy measurement with the electromagnetic calorimeter, allowing a significant improvement of the low transverse impulsion electrons measurement of the momentum, has been revisited and played an essential role in the Higgs boson discovery in the 4 leptons decay channel. The electron energy scale and resolution have been measured with very high precision using the Z boson decaying in electrons.Ce document de thèse traite de la mesure de la masse et de la largeur du nouveau boson découvert récemment au Large Hadron Collider (LHC), candidat pour être le boson de Higgs du modèle standard. L’analyse utlise les collisions protons-protons enregistrées par le détec- teur Compact Muon Solenoid (CMS) au LHC, correspondant à des luminosités integrées de 5.1 fb−1 à 7 TeV d’énergie dans le centre de masse et de 19.7 fb−1 à 8 TeV d’énergie dans le centre de masse. Les événements selectionnant le boson de Higgs via sa désintégration en ZZ, ou les bosons Z se désintègrent en paires d’électrons ou de muons, ont été exploités pour la mesure des propriétés du boson de Higgs. Une mesure précise de la masse a été effectuée et vaut 125.6 ± 0.4(stat) ± 0.2 (syst) GeV. Des contraintes sur la largeur du boson de Higgs ont été établies en utilisant sa production hors-masse et sa désintégration en une paire de bosons Z, ou un des Z se désintègre en paire d’électrons ou de muons, et l’autre en une paire d’électrons, de muons ou de neutrinos. Le résultat obtenu est une limite supérieure sur la largeur du boson de Higgs à 22 MeV à 95% de niveau de confiance, ce qui correspond à 5.4 fois la valeur attendue pour le modèle standard à la masse mesurée. Une attention particulière a été apportée à l’estimation de l’impulsion des électrons. La combinaison de l’estimation de l’impulsion par le trajectomètre et la mesure de l’énergie déposée dans le calorimètre électromagnétique, permettant une amélioration significative de la mesure de l’impulsion des électrons de bassse impulsion transverse, a été ré-optimisée et a joué un rôle essentiel dans la découverte du boson Higgs dans le canal en quatre leptons. L’échelle d’énergie ainsi que la résolution en énergie des électrons a été mesurée avec une grande précision en utilisant les bosons de Z se désintégrant en électrons
La Physique du Sport
No full textPhysics tends to understand the world and to find the laws which govern it. Physics of Sports consists in observing with a physicist’s eye the phenomena which happen on the fields. These fields are wide and this study is built on several points which capture our attention : - records sports : to understand the records of speed or strength sports, we focus on muscle contraction mechanisms. We extract the dynamics of a simple gesture at Bench Press and understand it through simple mechanics laws and microscopic model of muscle contraction. - badminton trajectories : we solve the equations of motion of a particle which undergoes gravity and aerodynamic drag (proportional to the velocity sqaure, for high Reynolds numbers) and extract an analytical expression of the range. At each time the launching velocity is higher than the terminal velocity (which is the constant velocity of vertical falling of the projectile under gravity and drag), one observes a Tartaglia triangular shape of the trajectory. It is the case for most of sports balls, for fireworks, for firemen water jets, for cannonballs... For all these trajectories, the range saturates with the initial velocity : even if you hit stronger, the ball will not go further. We show several applications of this property. For exemple in sport, as there is no use to play on a field which is larger than the useful length, the size of sports fields is bound to be linked to the maximal range of the associated ball, from table tennis to golf. - balls impacts : we study soccer kicks and focus on the way of kicking the ball. The toe poke is said to be more efficient than the push pass. We perform experiments which show that the ball velocity does not depend on the shape of the impactor, but only on the velocity of kicking. We then discuss some ways to enhance the impactor velocity by using joints or elasticity of the launcher.La Physique est la science qui cherche à comprendre le monde extérieur et à identifier les lois qui le régissent. La Physique du Sport consiste à observer des phénomènes qui se produisent sur un terrain de sport avec un œil de physicien. Son champ est très vaste et cette thèse est construite sur plusieurs thèmes qui ont attiré notre attention : - les sports à records : pour comprendre les records dans les sports de force ou de vitesse, nous nous sommes intéressés aux mécanismes de la contraction musculaire. L’étude de la dynamique de lever au développé couché, couplée à un modèle microscopique du muscle nous permet d’identifier les caractéristiques musculaires d’un athlète à partir d’un mouvement macrosco- pique. - les trajectoires triangulaires au badminton : nous avons résolu les équations du mouvement (avec une traînée proportionnelle au carré de la vitesse), et obtenu une équation analytique de la portée du projectile. Dans tous les cas où la vitesse initiale du projectile est supérieure à sa vitesse terminale (la grande majorité des ballons de sports, les feux d’artifice, les jets de lances à incendie, les boulets de canons...), la trajectoire est semblable à celle du volant du badminton, et la portée sature avec la vitesse initiale. Une conséquence en sport est que la taille des terrains, fixée empiriquement, est proportionnelle à la portée maximale de chaque sport, qui dépend uniquement des caractéristiques du bal- lon utilisé. Et cela est vrai de la table de tennis de table au parcours de golf. - les impacts de balles : nous avons étudié la frappe du ballon au foot et essayé de comprendre pourquoi une frappe du pointu est plus efficace qu’un plat du pied, comme les joueurs l’affirment. Nous avons montré que la vitesse du ballon est indépendante de la forme de l’impacteur, seule la vitesse du pied compte. Nous avons ensuite essayé de comprendre quelles straté- gies étaient employées en sport pour augmenter la vitesse de la balle et notamment l’effet élastique de la raquette de badminton lors d’un smash
Storage efficient and unconditionnally secure private information retrieval
No full textThe invention relates to storage of information in data storage servers, queries made to databases, and privacy of such queries
Numerical study of a macroscopic finite pulse model of the diffusion MRI signal
No full textInternational audienceDiffusion magnetic resonance imaging (dMRI) is an imaging modality that probes the diffusion characteristics of a sample via the application of magnetic field gradient pulses. The dMRI signal from a heterogeneous sample includes the contribution of the water proton magnetization from all spatial positions in a voxel.If the voxel can be spatially divided into different Gaussian diffusion compartmentswith inter-compartment exchange governed by linear kinetics, thenthe dMRI signal can be approximated using the macroscopic Karger model,which is a system of coupled ordinary differential equations (ODEs), under the assumption that the duration of the diffusion-encoding gradient pulses is shortcompared to the diffusion time (the narrow pulse assumption). \soutnew{Recently, a new macroscopic ODE model of the dMRI signal, the Finite Pulse ODE (FP-ODE) model,was derived from the Bloch-Torrey partial differential equation (PDE), without the narrow pulse restriction, using periodic homogenization techniques.}{Recently, a new macroscopic model of the dMRI signal,without the narrow pulse restriction, was derived from the Bloch-Torrey partial differential equation (PDE)using periodic homogenization techniques.} \soutnew{When restricted to narrowpulses, the FP-ODE model has the same form as the Karger model.}{When restricted to narrowpulses, this new homogenized model has the same form as the Karger model.} We conduct a numerical study of the \soutnew{FP-ODE}{new homogenized} model for voxels that are made up of periodic copies of a representativevolume that contains spherical and cylindrical cells of various sizes and orientationsand show that the signal predicted by the \soutnew{FP-ODE}{new} model approaches the reference signalobtained by solving the full Bloch-Torrey PDEin O(\veps^2), where \veps is the ratio between the size of the representativevolume and \soutnew{the diffusion displacement}{a measure of the diffusion length}.When the narrow gradient pulse assumption is not satisfied, the \soutnew{FP-ODE}{new homogenized} model offers a much better approximation of the full PDE signal than the Karger model.Finally, preliminary results of applying the \soutnew{FP-ODE}{new} model to a voxel that is not made up of periodic copies of a representativevolume are shown and discussed
The DREAMS experiment on the ExoMars 2016 mission for the study of Martian environment during the dust storm season
No full textInternational audienceThe ExoMars programme, which is carried out by European Space Agency (ESA) in cooperation with the Russian federal Space Agency (Roscosmos), foresees a two-steps mission to Mars. The first mission consists of an orbiter and an Entry Descent and Landing Demonstrator Module (EDM) to be launched in January 2016 and is scheduled to land on the planet during the statistical dust storm season; the second mission includes a descent module, a surface platform and a rover and will be launched in 2018. The DREAMS (Dust characterization, Risk assessment and Environment Analyser on the Martian Surface) experiment for ExoMars 2016 is an autonomous meteorological station designed to study the effect of dust on Martian environment which will operate for two Martian days (sols) relying on its own power supply after landing. DREAMS includes a suite of sensors able to analyse temperature, pressure, humidity, wind speed and direction and solar irradiance as well as an electric field probe which will perform the first electrical characterization of Mars surface atmosphere
Towards a theory for vortex filaments in stratified-rotating fluids
No full textInternational audienceIn inviscid fluids with uniform density, it is common to idealize three-dimensional vortex tubes by filaments (i.e., single lines of an infinitesimal cross section). Thanks to the Kelvin and Helmholtz theorems, it is known that these vortex filaments are transported with the fluid and their circulation is conserved. The induced motions can be computed by the Biot–Savart law, with an appropriate cut off in the integral to avoid singularity. Hence, this approach allows one to model the linear or nonlinear dynamics of vortex flows. A priori, vortex filaments cannot be used in density-stratified and rotating fluids since the circulation is not conserved and the vortex lines are not material lines. However, in this paper we review a theory that is equivalent to vortex filaments. It is based on matched asymptotic expansions for small vortex-core size, weak curvature, and small vortex displacements. The resulting stability equations are formally identical to those of vortex filaments in homogeneous fluids. However, striking differences between homogeneous and stratified-rotating fluids exist, such as the reversal of the self-induced motion for strong stratification or complex self-induction for moderate stratification due to the presence of critical points. The three-dimensional linear stability of vertical vortex pairs and vortex arrays (Karman street, double symmetric row) in stratified and rotating fluids has been investigated using this analytical approach. The results are in very good agreement with the results of direct numerical stability analyses of smooth vortex configurations. Possible extensions to include nonlinear and baroclinic effects are briefly discussed
Climatic Conditions and Productivity: An Impact Evaluation in Pre-industrial England
No full textIn this paper, we bridge economic data and climatic time series to assess the vulnerability of a pre-industrial economy to changes in climatic conditions. We propose an economic model to extract a measure of total productivity from English data (real wages and land rents) in the pre-industrial period. This measure of total productivity is then related to temperatures and precipitations. We find that lower (respectively higher) precipitations (resp. temperatures) enhance productivity. Further, temperatures also have non-linear effects on productivity : large temperature variations lower productivity. We perform counterfactual exercises and quantify the effects of large increases in temperatures on productivity, GDP and welfare
Bounding rare event probabilities in computer experiments
No full textInternational audienceBounding probabilities of rare events in the context of computer experiments is an important concern in reliability studies. These rare events depend on the output of a physical model with random input variables. Since the model is only known through an expensive black box function, standard efficient Monte Carlo methods designed for rare events cannot be used. That is why a strategy based on importance sampling methods is proposed. This strategy relies on Kriging meta-modeling and manages to achieve sharp upper confidence bounds on the rare events probabilities. The variability due to the Kriging meta-modeling step is properly taken into account. The proposed methodology is applied to an artificial example and compared with more standard Bayesian bounds. Eventually, a challenging real case is analyzed. It consists in finding an upper bound for the probability that the trajectory of an airborne load will collide with the aircraft that released it
Non-holonomic interpolation motion planning for the car with trailers
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