The central theme of this thesis is to discuss the depiction of nature in the work of the Chilean author María Luisa Bombal and to show how she introduces a woman's perspective into these texts. The emphasis is on finding t ypical symbols which are used in the author's novels and short stories and to focus on their specific usage and connotations. For greater clarit y, the author's work is divided into 3 major thematic units: seeking for love in vain, the cosmic connection of female characters wi th nature, and her interpretation of the relationship between life and death.

Le satellite Planck est le satellite de troisième génération visant à observer le fond diffus cosmologique. La résolution et la sensibilité de ses instruments permettent pour la première fois de mettre en évidence les effets de lentille gravitationnelle subis par les photons du fond diffus cosmologique. Cette thèse présente une méthode originale de détection de ces effets dans les données de l'instrument HFI de Planck.La première partie donne dans un premier temps, une description générale du modèle standard de la cosmologie et de la physique du fond diffus cosmologique. Elle aborde ensuite en détails l'effet de lentille gravitationnelle, en se concentrant plus particulièrement sur son impact sur les observables du fond diffus cosmologique. Elle termine par une présentation du satellite Planck et de ses instruments.La seconde partie se concentre sur la description d'un ensemble d'outils de simulations et d'analyse que j'ai développé au cours de ma thèse afin de réaliser la première détection des effets de lentille gravitationnelle sur le fond diffus cosmologique. Elle présente la méthode originale employée qui repose sur une analyse des cartes du ciel par morceaux, permettant de s'affranchir des zones du ciel les plus contaminées. On trouvera également dans cette partie une caractérisation, de l'estimateur du champ de potentiel de lentille, pour des cartes masquée, en présence de bruit inhomogène ainsi que la présentation d'une méthode pour corriger les biais de l'analyse à l'aide de simulations Monte-Carlo.La dernière partie, est consacrée au travail sur les données de l'instrument HFI. Le premier chapitre présente l'application de la méthode d'analyse précédente aux cartes des observations combinées à 143GHz et 217GHz ainsi que la carte issue de la séparation des composantes avec l'algorithme GMCA. Les résultats montrent un spectre de puissance de la déflexion compatible avec le spectre attendu, dans un modèle lambda CMB, calculé à partir des paramètres cosmologiques issus de WMAP intégrant sept années d'observations. Les points de mesure, issus du spectre combiné des cartes à 143GHz et 217GHz, pour les multipôles inférieurs à 500, donnent un Chi2 par degré de liberté de 1.26. Finalement, le dernier chapitre présente l'algorithme de compression des données de l'instrument HFI à bord du satellite. Il traite en détail le réglage et le suivi des paramètres de compression et du débit des données, depuis le lancement du satellite et fait le bilan sur les erreurs de compression rencontrées / The Planck satellite is the third generation experement dedicated to the observation of the cosmic microwave backgroud (CMB). The resolution and sensibility of its intruments allow for the first time the detection of the weak lensing effect on CMB. This thesis present a original detection method of this effect in the data of the HFI instrument of Planck.The first part give a general description of the standard model of cosmology et the physics of the CMB. The part then presents the details of the weak lensing effect, concentrating on its impact on the CMB observables. This part ends with a description of the Planck satellite and its instruments.The second part, discribes the set of simulations and analysis tools that I have developed allowding me to make the first mesureament of the weak lensing effect on CMB. It presents the original method that I used which is based on a patch analysis of the full sky data, that is able to only take into account the less contaminated regions. This part also present the caracterisation of the lensing potential estimator for masked maps in the presence of inhomogeneous noise and introduce a method, based on Monte-Carlo simulations, that is used to correct for the biais produced by the analysis method.The last part, concentrates on the work on HFI data. The first chapter presents the application of the above method to the maps of the combined observations at 143GHz and 217GHz and the maps from component separation using GMCA algorithm. The results show a deflection power spectrum compatible with the one expect in a lambda CMB universe, calculated with the cosmological parameters estimated by WMAP including seven years of observations. Using the points, from the combined estimation from the 143GHz and 217GHz maps, for multipole smaller than 500, gives a 1.26 Chi2 by degree of freedom. Finally, the last chapter presents the comression algorithm used onboard to compression HFI data. It gives the details of the tunning and the following of the compression parameters and the data rate, since the launch and summarize the results on the compression errors

Extreme Universe Space Observatory on Japanese Experiment Module (JEM-EUSO) est conçu comme l’expérience de rayons cosmiques de prochaine génération pour observer les particules hautement énergétiques au-dessus de 10²⁰ eV. Le projet est mené par RIKEN et soutenu par une collaboration de plus de 200 membres provenant de 13 pays. Cet observatoire, sous la forme d'un télescope fluorescent, sera arrimé à la Station Spatiale internationale (ISS) pour un lancement prévu en 2017. En observant les gerbes atmosphériques produites dans la troposphère, à une altitude de 400 km, cet observatoire de rayons cosmique offrira une grande surface de détection, qui est au moins 100 fois supérieur que le plus grand détecteur de rayons cosmiques jamais construit. La surface focale de JEM-EUSO sera équipée d'environ 5000 unités de photomultiplicateur multianode 8x8 pixels (MAPMT). Un circuit intégré (ASIC), connu sous le nom SPACIROC, a été proposé pour la lecture du MAPMT. Cet ASIC de 64 voies propose des fonctionnalités comme le comptage de photons, la mesure des charges et le transfert de données à haute vitesse. Par-dessus tout, cet ASIC doit peu consommé afin de respecter la contrainte de puissance de JEM-EUSO. Réalisé en utilisant la technologie AMS Silicium-Germanium (SiGe) 0,35 µm, cet ASIC intègre 64 canaux de comptage de photons rapides (Photon Counting). La résolution de temps pour le comptage de photons est de 30 ns, ce qui permettra d’atteindre la valeur maximale comptage qui est de l'ordre de 10⁷ photons / s. Le système de mesure de charge est basé sur le Time-Over-Threshold qui offre 8 canaux de mesure. Chaque canal de mesure est une somme des 8 pixels du MAPMT et il est prévu que ce système est capable de mesurer jusqu'à 200 pC. La partie numérique fonctionne en continu et gère la conversion des données de chaque voie des blocs de Photon Counting et Time-Over-Threshold. Les données numériques sont transmises par l'intermédiaire de liaisons parallèles dédiées et ces opérations sont effectuées pendant une fenêtre de communication ou « Gate Time Unit » (GTU) de fréquence 400 kHz. Le taux de transfert des données d’ASIC avoisine les 200 Mbps ou 576 bits / GTU. La dissipation de puissance est strictement inférieure à 1 mW par canal ou 64 mW pour l'ASIC. Le premier prototype de SPACIROC a été envoyé pour fabrication en Mars 2010 au Centre Multi Projet (CMP). Des puces nues et packagés ont été reçues en Octobre 2010, ce qui a débuté la phase de caractérisation de cet ASIC. Après une phase de test réussie, des puces SPACIROC ont été intégrés dans l'électronique frontale d'un instrument pour détecter les sursauts gamma - Ultra Fast Flash Observatoire (UFFO) qui va être lancé en 2013. Vers la fin de l'année 2012, des cartes électroniques frontales conçues autour des puces SPACIROC ont été fabriqués pour le projet EUSO-Balloon. Ce projet de vol en ballon stratosphérique à une altitude de 40 km servira comme le démonstrateur technologique et l'ingénierie d'un instrument miniaturisé JEM-EUSO. La deuxième génération de cet ASIC a été envoyée à la fonderie en Décembre 2011. Ce second prototype, SPACIROC2, a été testé à partir de mai 2012. Les principales améliorations sont les suivantes: la consommation d'énergie a été revue à la baisse, ainsi que l'amélioration de la résolution temporelle de Photon Counting et l'extension de la gamme dynamique pour le module Time-Over-Threshold. Les mesures en cours ont montré que SPACIROC2 présente un bon comportement général et apporte des améliorations par rapport à son prédécesseur. / Extreme Universe Space Observatory on Japanese Experiment Module (JEM-EUSO) is conceived as the next generation cosmic rays experiment for observing the highly energetic particles above 5.10¹⁹ eV. The project is lead by RIKEN and supported by an active collaboration of more than 200 members from 13 countries. This observatory, in the shape of a wide field-of-view UV telescope, will be attached to the International Space Station (ISS) for a planned launch in 2017. Observing the Air Showers generated in troposphere from an altitude of 400 km, this space based cosmic rays experiment will offer a very large instantaneous detection surface, which is at least 100 times bigger than the largest land based cosmic rays observatory. The detection surface of JEM-EUSO will be equipped with around 5000 units of 8x8 pixels Multianode Photomultiplier (MAPMT). A radiation hardened mixed signal application-specific integrated circuit (ASIC), known as SPACIROC, has been proposed for reading out the MAPMT. This ASIC features 64-channel analog inputs, fast photon counting capabilities, charge measurements and high-speed data transfer. Above all, the power dissipation of this ASIC is required to be very low in order to comply with the strict power budget of JEM-EUSO. By taking the advantages of high speed AMS 0.35 µm Silicon-Germanium (SiGe) process, this ASIC integrates 64 fast Photon Counting channels. The photon counting time resolution is 30 ns, which allows the theoretical counting rate in the order of 10⁷ photons/s. The charge measurement system is based on Time-Over-Threshold which offers 8 measurement channels. Each measurement channel is composed of 8 pixels of the MAPMT and it is expected that this system will measure up to 200 pC. The digital part is then required to operate continuously and handles data conversion of each Photon Counting and Time-Over-Threshold channel. For the first version of this ASIC, one channel measurement channel for the dynode is also available. The digital data are transmitted via dedicated parallel communication links and within the defined Gate Time Unit (GTU) of 400 kHz frequency. The ASIC data output rate is in the vicinity of 200 Mbps or 576 bits/GTU. The power dissipation is kept strictly below 1 mW per channel or 64 mW for the ASIC. The first prototype of SPACIROC was sent for tapeout in March 2010 through Centre Multi Projet (CMP) prototyping services. The packaged ASICs and bare dies have been received in October 2010 which marked the characterization phase of this chip. After successful testing phase, SPACIROC chips were integrated into the front-end electronics of an instrument pathfinder for detecting the gamma ray bursts – Ultra Fast Flash Observatory (UFFO) which is foreseen to be launched in 2013. Towards the end of 2012, front-end board designed around SPACIROC chips have been fabricated for the EUSO-Balloon project. This balloon borne project will serve as a technical and engineering demonstrator of a fully miniaturized JEM-EUSO instrument which will be flown to the stratosphere at the altitude of 40 km. The second tapeout of this ASIC was done in December 2011. This second prototype, SPACIROC2, was tested from May 2012. The main improvements are as follows: lower power consumption due to better power management, enhancement in Photon Counting time resolution and extension the Time-Over-Threshold maximum input rate. The ongoing tests have shown that SPACIROC2 exhibits a good overall behavior and improvement compared to its predecessor.

Le fond diffus cosmologique (CMB), relique du Big-Bang chaud, porte les traces à la fois de la formation des structures des époques récentes et des premières phases énergétiques de l'Univers.Le satellite Planck, en service de 2009 à 2013, a fourni des mesures de haute qualité des anisotropies du CMB. Celles-ci sont utilisés dans cette thèse pour déterminer les paramètres du modèle cosmologique standard et autour du secteur des neutrinos.Ce travail décrit la construction d'un fonction de vraisemblance pour les hauts-l de Planck. Cela implique une stratégie de masquage pour l'émission thermique de la Galaxie ainsi que pour les sources ponctuelles. Les avant-plans résiduels sont traités directement au niveau du spectre de puissance en utilisant des templates physiques bases sur des études de Planck.Les méthodes statistiques nécessaires pour extraire les paramètres cosmologiques dans la comparaison entre les modèles et les données sont décrites, à la fois la méthode bayésienne de Monte-Carlo par chaînes de Markov et la technique fréquentiste du profil de la fonction de vraisemblance.Les résultats sur les paramètres cosmologiques sont présentés en utilisant les données de Planck seul et en combinaison avec les données à petites échelles des expériences de CMB basées au sol (ACT et SPT), avec les contraintes provenant des mesures des oscillations acoustiques des baryons (BAO) et des supernovae. Les contraintes sur l'échelle absolue de la masse des neutrinos et sur le nombre effectif de neutrinos sont également discutées. / The cosmic microwave background (CMB), relic of the hot Big-Bang, carries the traces of both the rich structure formation of the late time epochs and the energetic early phases of the universe.The Planck satellite provided, from 2009 to 2013, high-quality measurements of the anisotropies of the CMB. These are used in this thesis to determine the parameters of the standard cosmological model and of the extension concerning the neutrino sector. The construction of an high-l Planck likelihood is detailed. This involves a masking strategy that deals in particular with the contamination from thermal emission of the Galaxy. The residual foregrounds are treated directly at the power spectrum level relying on physically motivated templates based on Planck studies.The statistical methods needed to extract the cosmological parameters in the comparison between models and data are described, both the Bayesian Monte Carlo Markov Chain techniques and the frequentist profile likelihood. Results on cosmological parameters are presented using Planck data alone and in combination with the small scale data from the ground based CMB experiment ACT and SPT, the Baryon Acoustic Oscillation and the Supernovae. Constraints on the absolute scale of neutrino masses and of the number of effective neutrino are also discussed.

Há várias evidências experimentais da existência de matéria escura no universo. Apesar destas evidências, pouco se sabe sobre sua constituição, sabendo-se apenas que interage gravitacionalmente, mas não eletromagneticamente. Neste projeto, investigamos a possibilidade da matéria escura ser composta por partículas supermassivas e fortemente interagentes (Simpzillas). Para isto determinamos o sinal que deve ser deixado no telescópio IceCube por neutrinos resultantes de aniquilações de matéria escura no Sol. Após determinarmos o espectro de neutrinos no centro do Sol, simulamos sua propagação até a superfície, depois até a Terra e através da Terra até o detector. Comparamos então estes resultados com os fornecidos pelo IceCube. Esta comparação permite testar uma região do espaço de fase massa versus seção de choque previamente não-excluída por outros tipos de experiência que não telescópios de neutrinos. Como resultado, concluímos que partículas supermassivas e fortemente interagentes não podem constituir a matéria escura. / There are many experimental evidences for the existence of dark matter in the universe. Despite these evidences, there is no knowledge about its constitution other than the fact that it interacts gravitationally but not electromagnetically. In this project, we investigate the possibility that dark matter is composed of strongly interacting massive particles (Simpzillas). We determine the expected signal in the IceCube telescope from Simpzilla annihilation in the center of the Sun. We first determine the neutrino spectrum in the core of the Sun. We then simulate its propagation through both the Sun and Earth, and finally the rate of neutrinos at the detector. A comparison of these results to the ones published by the IceCube collaboration covers a large region of the yet not excluded regions of the mass versus cross-section phase space. As a result, the possibility of Simpzillas composing the dark matter is ruled out.

A determinação da massa de raios cósmicos ultra energéticos é uma questão em aberto devido a flutuação natural da primeira interação e o desconhecimentos da seção de choque para altas energias (E > 1017 eV). Alguns estudos (1) mostraram que modificações sistemáticas das propriedades em interações hadrônicas interfere significativamente no desenvolvimento de chuveiros atmosféricos extensos e, consequentemente, provêm diferentes interpretações para os resultados de raios cósmicos. No limite de altas energias, pode ocorrer a saturação de glúons na superfície nuclear, o que resulta no aumento da seção de choque próton-próton e próton-núcleo em relação ao modelo de Glauber. A seção de choque cresce com a energia e está relacionada com a função de distribuição de probabilidade de encontrar um centro espalhado que é maior no modelo de saturação de glúons. Neste trabalho analisamos a seção de choque próton-ar e núcleo-ar para energias acima de 1018 eV usando a hipótese da saturação de glúons (2). Implementamos a saturação de glúons no modelos de interações hadrônicas de altas energia SIBYLL e estudamos o desenvolvimento do chuveiro atmosférico extenso usando o programa CORSIKA. Comparamos os resultados com a taxa de elongação medida pelo Observatório Pierre Auger. Concluímos mostrando o efeito da saturação de glúons na interpretação na composição da massa de raios cósmicos ultra energéticos. / The determination of the composition of ultra high energy cosmic rays is an open question due to natural fluctuations of the first interaction point and unknow high energy cross sections. Some studies (1) have shown that systematic modifications in the hadronics interaction properties infer significantly in the development of extensive air showers and, consequently, provides different interpretations of cosmic ray results. In high energy limit (E > 1018eV), gluon saturation may occur in the nuclear surface region, so that the cross section proton-proton and proton-nucleus increase more rapidly with incident energy than Glauber theory. The cross section rise with energy is related to the probability distribution function of scattering centers which is larger for gluon saturation models. In this work we analyze the cross section proton-proton and proton-nucleus at energies above 1018 eV using the gluon saturation hypothesis (2). We implemented the gluon saturation physics in the SIBYLL hadronic interaction model and we studied the development of the air shower using the CORSIKA program. Different extrapolation models of high energy interaction with gluon interaction have been implemented in SIBYLL. We compared the simulation results using gluon saturation with the measured elongation rate published by the Pierre Auger Collaborations. We conclude by showing the effect of gluon saturation in the interpretation of cosmic ray by composition.

O comportamento das interações hadrônicas para energias de centro de massa superiores a 50 TeV/núcleon é uma fonte importante de incerteza sistemática na interpretação de dados de observatórios de raios cósmicos. Nesta tese, estudamos por meio de simulações de Monte Carlo observáveis dos chuveiros atmosféricos que pudessem ser correlacionados com aspectos dos diferentes modelos destas interações. Especial atenção foi dada à componente muônica que sabidamente é gerada do decaimento de partículas de natureza hadrônica na cascata. A precisão e a acurácia de uma rede esparsa de contadores de múons foram estudadas como função da granularidade da rede de detectores e da área de coleção de suas células. Mostramos, em particular, as diferenças na dependência radial da densidade de múons no plano transversal ao eixo da cascata para os diferentes modelos. Tais diferenças se mostram mais acentuadas na vizinhança do eixo e poderiam ser exploradas experimentalmente com um detector com alcance dinâmico suficiente para evitar saturação da eletrônica. Além disso, por meio de um tratamento fenomenológico, investigamos o impacto no desenvolvimento do chuveiro causado por variações na distribuição de pseudorapidez $dN/d\\eta$ de secundários produzidos na colisão primária. Mostramos que diferentemente de quantidades como seção de choque inelástica, multiplicidade, razão de carga e elasticidade, mudanças em $dN/d\\eta$ que preservem tais quantidades são rapidamente diluídas nas sucessivas camadas de interações posteriores à colisão primária. / The behavior of the hadronic interactions at center of mass energies greater than 50 TeV/nucleon is an important source of systematic uncertainty on interpreting data from cosmic ray observatories. In this thesis, we study through Monte Carlo simulations the atmospheric shower observables that could be correlated with different aspects of these interactions. Special attention was paid to the muonic component that is known to be generated from the decay of hadronic particles. The precision and accuracy of a sparse grid of muon counters were studied as a function of the array granularity and the collection area of its cells. In particular, we studied the differences in the radial dependence of the muon density in the shower plane for different models. These differences are shown to be larger in the vicinity of the shower axis and, therefore, could be explored with a detector of sufficiently large dynamic range as to avoid saturation of its acquisition electronics. In addition, through a phenomenological treatment, we investigated the impact on the shower development caused by variations in the distribution of pseudorapidity $ dN/d\\eta $ of secondaries particles produced in the primary collision. We show that unlike quantities such as inelastic cross section, multiplicity, charge ratio and elasticity, changes in $ dN/d\\eta $ that preserve such quantities are rapidly diluted in successive interaction layers subsequent to the primary collision.

The cosmic rays are the most energetic particles in the universe. Their production, propagation, and detection are objects of studies. Surface detectors aim to identify particles from extensive air showers (EAS) which the result from the cosmic-ray interactions with the atmosphere. Resistive Plate Chambers (RPCs) have shown to be a suitable muon detector to be integrated into the Pierre Auger Observatory. An instrumentation was developed to assembly RPCs in São Carlos (BRA). Data from RPCs already built by our collaborators in Coimbra (POR) were analyzed. The detector efficiency to muons was calculated and is approximately 88%, which is in good agreement with the values quoted in the literature. Direction maps were built to investigate the muon incoming direction and the quantity of matter traversed by the muons. The dependence of the muon flux on the zenith angle was calculated and compared with results from the simulation. A square cosine dependence is expected, though it is seen that the building structure has enough matter to block some of the incident muons and alter the dependence curve. The total muon flux was estimated based on the detector efficiencies and solid angle as 1.6.10−5. mm−2.sr−1. s−1 compared with the literature value of 7.1.10−5 mm−2.sr−1.s−1, which gives an absorption by the building of approximately 77%. / Os raios cósmicos são as partículas mais energéticas do universo. Sua produção, propagação e detecção são objetos de estudos. Os detectores de superfície têm como objetivo identificar partículas dos chuveiros atmosféricos extensos (EAS), o qual é o resultado das interações do raio cósmico com a atmosfera. A Câmaras de Placas Resistivas (RPCs) demonstra ser um detector de múons adequado para ser integrado ao Observatório Pierre Auger. Foi desenvolvida em São Carlos (BRA) uma instrumentação para montagem de RPCs. Dados de RPCs já construídas por nossos colaboradores em Coimbra (POR) foram analisados. A eficiência dos detectores para múons foi calculada como sendo de aproximadamente 88%, o que está de acordo com os valores citados na literatura. Mapas de direção foram construídos para investigar a direção de chegada e a quantidade de matéria atravessada pelos múons. A dependência do fluxo de múons com o ângulo zenital foi comparada com os resultados da simulação. Embora uma dependência com o quadrado do cosseno é esperada, foi constatado que a estrutura do prédio tem matéria suficiente para bloquear parte dos múons incidentes e alterar a curva da dependência. O fluxo total de múons foi estimado baseado nas eficiências do detector e no ângulo sólido é de 1.6.10−5 mm−2.sr−1.s−1. Comparado com o valor da literatura de 7.1.10−5 mm−2.sr−1.s−1 resulta em uma absorção pelo prédio de aproximadamente 77% do fluxo de múons.

A hipótese de que a matéria estranha de quarks (um plasma composto por quarks up, down e strange em quantidades aproximadamente iguais) é estável `a pressão nula vem sendo considerada há mais de vinte anos, tanto teoricamente quanto em experimentos específicos para sua eventual detecção. Se a matéria estranha é de fato estável, então poderia haver importantes implicações para a Astrofísica. Entre as mais estimulantes destas implicações está a possibilidade de conversão da matéria nuclear ordinária em matéria estranha no interior das estrelas de nêutrons devido ás altíssimas densidades ali encontradas. Processos tais como coalescência em binárias de estrelas de nêutrons e as próprias supernovas, eventos responsáveis pelo nascimento destas estrelas, poderiam ejetar estruturas finitas de matéria estranha, chamadas strangelets (equivalentes aos núcleos), no meio interestelar. Desta forma, strangelets estariam presentes entre os primários de raios cósmicos e seriam sujeitas a processos elementares análogos aos núcleos ordinários. Nesta Tese, as strangelets são estudadas desde os prováveis sítios para sua produção astrofísica, passando por interações com a matéria do meio interestelar, ate a chegada ás imediações terrestres. Estima-se o fluxo de strangelets de baixa energia que poderia ser mantido aprisionado na magnetosfera da Terra, bem como são estudados os processos de suas interações com componentes da atmosfera, com vistas às assinaturas observacionais então resultantes. Desta forma, são determinadas as características relevantes para a identificação destes exóticos por experimentos que testam o fluxo de raios cósmicos, ajudando na melhor compreensão das propriedades da matéria nuclear em alta densidade bariônica e baixa temperatura. / The strange quark matter hypothesis, which states that a plasma composed of quarks up, down and strange in roughly equal amounts is absolutely stable at zero pressure, has been studied for more than twenty years, both theoretically and during searches for its detection in specific experiments. If strange quark matter is indeed stable, then there could be important implications for the field of Astrophysics. Among the most stimulating ones is the possibility of conversion of ordinary nuclear matter in strange quark matter in the interior of neutron stars due to the extremely high densities reached in the core of these compact objects. Processes such as the merger in neutron star binaries systems and supernovae themselves, responsible for the birth of these stars, may eject lumps of strange quark matter, termed strangelets, in the interstellar medium. In this way, strangelets may be present among the cosmic ray flux and be subjected to elementary processes much in the same way as ordinary nuclei. In this Thesis, strangelets are studied from their likely astrophysical production sites, passing through the interstellar medium until they reach the Earth neighborhood. Estimates of the low energy flux of strangelets that could be trapped in the terrestrial magnetosphere are given. Also, the interaction of these particles with components in the Earth atmosphere are studied with the aim of providing better understanding of the resulting observational signatures. It allows the determination of the relevant characteristics for the identification of these exotics by experiments testing the cosmic ray flux, helping to better understand the properties of nuclear matter at high densities and low temperatures.

Les aérosols atmosphériques à l'Observatoire Pierre Auger : caractérisation et effet sur l'estimation de l'énergie des rayons cosmiques d'ultra-haute énergie.L'Observatoire Pierre Auger, situé dans la province de Mendoza en Argentine, réalise actuellement de grandes avancées dans la connaissance de la nature et de l'origine des rayons cosmiques d'ultra-haute énergie. Utilisant une technique de détection hybride, basée sur des détecteurs de surface et des télescopes de fluorescence, il fournit une large statistique, une bonne résolution en énergie, et un contrôle solide des incertitudes systématiques.L'un des principaux défis pour la technique de détection par fluorescence est la compréhension de l'atmosphère, utilisée comme un calorimètre géant. Afin de réduire autant que possible les incertitudes systématiques sur les mesures par fluorescence, la Collaboration Auger a développé un important programme de suivi de l'atmosphère. Le but de ce travail est d'améliorer notre compréhension sur les aérosols atmosphériques, ainsi que leur effet sur la propagation de la lumière de fluorescence.En utilisant un modèle de rétrotrajectographie des masses d'air, il a été montré que les nuits pauvres en aérosols ont des masses d'air provenant plus directement de l'Océan Pacifique. Pour la première fois, l'effet de la taille des aérosols sur la propagation de la lumière a été estimé. En effet, selon l'approche Ramsauer, les gros aérosols ont le plus grand effet sur la diffusion de la lumière. Ainsi, la dépendance en taille a été ajoutée aux paramétrisations décrivant la diffusion de la lumière et utilisée par la Collaboration Auger. Une surestimation systématique de l'énergie et du maximum de développement de la gerbe Xmax est observé.Enfin, une méthode basée sur les tirs laser très incliné produit par le laser central d'Auger a été développée pour estimer la taille des aérosols. Des tailles d'aérosols jusque là jamais détectées à l'Observatoire Pierre Auger peuvent à présent être contraintes. De premiers résultats montrent une population d'aérosols de grande taille en utilisant des tirs laser effectués dans le passé. / Atmospheric aerosols at the Pierre Auger Observatory: characterization and effect on the energy estimation for ultra-high energy cosmic rays.The Pierre Auger Observatory, located in the Province of Mendoza in Argentina, is making good progress in understanding the nature and origin of the ultra-high energy cosmic rays. Using a hybrid detection technique, based on surface detectors and fluorescence telescopes, it provides large statistics, good mass and energy resolution, and solid control of systematic uncertainties.One of the main challenges for the fluorescence detection technique is the understanding of the atmosphere, used as a giant calorimeter. To minimize as much as possible the systematic uncertainties in fluorescence measurements, the Auger Collaboration has developed an extensive atmospheric monitoring program. The purpose of this work is to improve our knowledge of the atmospheric aerosols, and their effect on fluorescence light propagation.Using a modelling program computing air mass displacements, it has been shown that nights with low aerosol concentrations have air masses coming much more directly from the Pacific Ocean. For the first time, the effect of the aerosol size on the light propagation has been estimated. Indeed, according to the Ramsauer approach, large aerosols have the largest effect on the light scattering. Thus, the dependence on the aerosol size has been added to the light scattering parameterizations used by the Auger Collaboration. A systematic overestimation of the energy and of the maximum air shower development Xmax is observed.Finally, a method based on the very inclined laser shots fired by the Auger central laser has been developed to estimate the aerosol size. Large aerosol sizes ever estimated at the Pierre Auger Observatory can now be probed. First preliminary results using laser-shot data collected in the past have identified a population of large aerosols.