Dans la continuité des expériences SuperKamiokande et K2K, OPERA (Oscillation Project with Emulsion tRacking Apparatus), cherchera à confirmer l'oscillation des neutrinos dans le secteur atmosphérique. Utilisant une technique déjà employée dans CHORUS et DONUT, la chambre à brouillard d'émulsion (Emulsion Cloud Chamber (ECC)), cette expérience permettra la mise en évidence de l'oscillation nµ® nt par apparition de nt dans un faisceau pur de nµ.<br />L'expérience OPERA, avec ses ~100000 m2 d'émulsions nucléaires, nécessite l'utilisation de systèmes de scan automatiques ultra rapides. Les composantes optiques et mécaniques de ces systèmes ont été optimisées pour atteindre une vitesse de scan de ~20 cm2/heure par couche d'émulsion (44 μm d'épaisseur), tout en gardant une résolution sub-micrométrique.<br />Dans la première partie de mon travail de thèse, je me suis consacrée à l'optimisation des 4 systèmes de scan au sein de l'unique station de scan française basée à Lyon. Une étude expérimentale sur les performances d'un scan utilisant un objectif à sec a été également réalisée. Les résultats obtenus montrent que les performances d'un scan « à sec » sont similaires à celles d'un scan traditionnel utilisant un objectif à huile. <br />La deuxième partie de mon travail a consisté à valider la stratégie actuellement utilisée dans OPERA pour la localisation et la reconstruction des vertex de l'interaction des neutrinos, à l'aide d'un test sur faisceau dédié. Les résultats obtenus confirment définitivement que la stratégie proposée est bien adaptée à la recherche du lepton tau.

We study the sensitivity of fixed target neutrino experiments (LSND, T2K, CENNS, and COHERENT) and proton beam dumps (MiniBooNE off-target, and SHiP) to sub-GeV dark matter. In order to reproduce the observed thermal relic abundance, these states are coupled to the Standard Model via new, low mass mediators in the form of a kinetically mixed U(1)0 vector mediator or a vector mediator gauging baryon number. We present a model for the production of low mass dark matter from proton-nucleon collisions in fixed targets. Sensitivity projections are made using signals from elastic electron- and nucleon-dark matter scattering, as well as coherent nuclear-dark matter scattering and dark matter induced inelastic π 0 production. A fixed target Monte Carlo code has been developed for this analysis, and documentation is included. We find that analyses using current and future proton fixed target experiments are capable of placing new limits on the hidden sector dark matter parameter space for dark matter masses of up to 500\,MeV and mediator masses as large as a few GeV. / Graduate

This Master thesis aims at designing, assembling and operating a prototypal luminescentbolometer containing a candidate with high Q-value (116Cd and 100Mo)for the study of the neutrinoless double- decay. The crystal is scintillating (with 116CdWO4 and Li2MoO4 compounds). The prototype is designed according to a simple thermal model and cooled down to 18 mK. Data analysis of the 116CdWO4 crystal determines the energy resolution (intrinsicand in the ROI) and the alpha/beta discrimination power. It includes a full interpretation of the background energy spectrum in terms of environmental radioactivity and an evaluation of the crystal radiopurity by the detection of internal contamination of the detector. An evaluation of the potential of a future experiment based on the 116CdWO4developed prototype is performed, ascertaining the feasibility of large scale experiments to search for neutrinoless double beta decay. The use of the thermal model of the detector response to interpret its bolometric behaviour and the study of future optimizations of the detector performance concludes this project.

[pt] Nesta dissertação, estudamos do ponto de vista fenomenológico, os efeitos de neutrinos estéreis para os observáveis de massas de neutrinos baseado nos dados do experimento LSND e nos resultados divulgados recentemente pela colaboração MiniBooNE. Consideramos observáveis de massa as seguintes quantidades: o parâmetro de massa cinemática cuja medida é realizada em experimentos com o decaimento beta do tritium tendo seu valor atual fornecido pelos experimentos Mainz e Troitsk; a massa efetiva de Majorana, que é uma quantidade que pode ser obtida em experimentos com o duplo decaimento beta sem neutrinos; finalmente, a soma de massas dos neutrinos, a qual é vinculada por dados cosmológicos. Nossa análise é realizada considerando os possíveis ordenamentos de massas para o caso em que temos dois neutrinos estéreis além dos três neutrinos ativos usuais, cuja adição é necessária para explicar os resultados de LSND e MiniBooNE ao mesmo tempo. Neste cenário, temos oito possíveis ordenamentos de massas, os quais dividimos em três grupos. No primeiro grupo, temos que os dois neutrinos estéreis são mais pesados que os três neutrinos ativos. No segundo grupo, os dois neutrinos estéreis são mais leves que os três neutrinos ativos. Cada um destes dois grupos tem possibilidades que dependem do ordenamento de massas dos neutrinos ativos que pode ser normal ou invertido. No terceiro e último grupo temos que um neutrino estéril é mais leve e o outro mais pesado que os três neutrinos ativos. Neste grupo, existem quatro possibilidades de ordenamento associada ao posicionamento dos neutrinos estéreis e ao ordenamento dos neutrinos do setor ativo. Investigamos os observáveis de massas em cada um destes cenários. / [en] In this dissertation we study, from the phenomenological point of view, the effects of sterile neutrinos for the observables related to neutrino masses based on the data of the LSND experiment and on the results releasedrecently by the MiniBooNE collaboration. We consider the following mass related obsevables: the kinematic mass parameter which is obtained in tritium beta decay experiments whose current value is provided by Mainzand Troitsk experiments; the Majorana effective mass, it is a quantity that can be obtained in neutrinoless double beta decay experiments. In additionto these quantities, we also consider the sum of neutrinos masses, which isconstrained by cosmological data. Our analysis is performed by considering the possible mass orderings for the cases where we have two sterile neutrinosbeyond the three standard active neutrinos, whose addition is necessary to explain the results of LSND andMiniBooNE simultaneously. In this scenariot here are eight possible mass orderings, which are divided into three groups.In the first group we have two sterile neutrinos which are heavier thanthe three active neutrinos. In the second group the two sterile neutrinosare lighter than the three active neutrinos. Each of these two groups canbe further divided into 2 subgroups depending on the mass ordering ofthe active neutrinos that can be normal or inverted. In the third and lastgroup we have one sterile neutrino lighter and the other heavier than thethree active neutrinos. In this group there are four possibilities of ordering depending on the positioning of the sterile neutrinos with respect to theactive ones and on the mass ordering of the active states. We investigate systematically the masses observable in each of these scenarios.

In this thesis we studied dark matter models with strong self-interactions, typically known as self-interacting dark matter (SIDM). This kind of models constitute a promising solution to the tension between small scale structure observations and predictions assuming the standard case of collisionless cold dark matter (CDM) while keeping the success of the standard cosmological model, LambdaCDM, at large scales. The presence of strong self-interactions can increase the dark matter capture and annihilation in astrophysical objects like our sun, enhancing the potential of indirect detection signals. We used the high energy neutrinos produced by such annihilations to probe SIDM models. We established strong constraints on SIDM with velocity independent cross section by comparing the expected neutrino signal with the results of the IceCube-79 dark matter search. Also, we determined the sensitivity for the IceCube-DeepCore and PINGU detectors for SIDM with a velocity dependent self-interacting cross section (vdSIDM). Most of its relevant parameter space can be tested with the three years of data already collected by IceCube-DeepCore, complementing results from direct detection experiments and other indirect detection studies. / Nesta tese investigamos modelos de matéria escura com auto-interações fortes, conhecidos tipicamente como matéria escura auto-interagente (SIDM). Este tipo de modelos constituem uma solução promissora à tensão entre as observações de estrutura a pequena escala e as previsões assumindo o caso padrão de matéria escura fria não colisional (CDM), enquanto se mantêm o sucesso do modelo cosmológico padrão, LambdaCDM, a grandes escalas. A presença de auto-interações fortes podem aumentar a captura e a aniquilação da matéria escura em objetos astrofísicos como o nosso sol, aumentando o potencial de sinais de detecção indireta. Usamos o sinal de neutrinos de alta energia produzidos por essas aniquilações para explorar modelos de SIDM. Estabelecemos fortes vínculos em modelos de SIDM com seção de auto-interação independente da velocidade comparando o sinal de neutrinos esperado com os resultados de busca de matéria escura do IceCube-79. Também, determinamos a sensibilidade dos detectores IceCube-DeepCore e PINGU para modelos de SIDM com uma seção de auto-interação dependente da velocidade (vdSIDM). A maior parte do espaço de parâmetros de interesse pode ser testado com os três anos de dados já coletados pelo IceCube-DeepCore, complementando os resultados de experimentos de detecção direta e outras an análises de detecção indireta.

O objetivo desta dissertação foi estudar os sinais que neutrinos provenientes de supernovas galáticas poderão produzir em detectores futuros, através de simulações de eventos observados na Terra por um detector Cherenkov pela reação de decaimento beta inverso. Por ser um local único em que neutrinos se encontram em condições de equilíbrio térmico, a física de neutrinos de supernova pode ser fonte de novo conhecimento na física de partículas elementares. Iniciamos o trabalho apresentando os aspectos mais importantes da física de neutrinos tal como é conhecida hoje, seguido de um estudo do papel do neutrino na explosão de uma supernova do tipo II e a influência das oscilações em futuras observações. As simulações foram feitas primeiramente considerando uma supernova de potencial estático, com a determinação de limites nos principais parâmetros que descrevem sua dinâmica. Utilizamos os casos de hierarquia normal e inversa e ângulos de mistura nos limites totalmente adiabático e não-adiabático. Posteriormente consideramos uma supernova de potencial dinâmico, a partir da qual estudamos o comportamento das probabilidades de transição e o perfil do espectro detectado nos mesmos casos anteriores. Com este potencial também foi possível observar o comportamento temporal do espectro e como este pode ser modificado com a hierarquia e ângulo de mistura. Mostramos que em uma futura detecção, o número de eventos e conseqüentemente sua variação com parâmetros de supernova não terão interferência considerável do efeito de onda de choque. Contudo, este pode causar distorções no espectro energético e temporal que poderão ter papel importante na determinação da hierarquia de massa e maior delimitação do ângulo de mistura. / The goal of this dissertation is to study the signals that supernova neutrinos could produce in future detectors, through simulations of events observed on Earth by a Cherenkov detector and inverse beta decay reaction. Since a supernova has been the only situation in which neutrinos are able to reach thermal equilibrium, the physics of supernova neutrinos can be source of a new knowledge in physics of elementary particles. We begin this work presenting the most important aspects of neutrino physics as known today, and then studying the role of neutrino in a type II supernova explosion and the oscillation influence in future observations. The simulations were initially performed considering a static potential, defining limits for the main parameters that describe its dynamics. We considered the cases of normal and inverse mass hierarchy and mixing angles within fully adiabatic and non-adiabatic limits. Later we used a supernova dynamic potential to study behavior of transitions probabilities and the profile of the spectrum detected in these previous cases. From this potential we also observed the temporal behavior of the spectrum and how it can be modified with the hierarchy and the mixing angle. We show that, in a future detection, the number of events and hence their variations with supernova parameters, will not suffer interference of the shock wave effect. However, this effect can cause distortions in the energy and time spectrum that could have an important role in determining the mass hierarchy and better constraints for the mixing angle.

Les progrès réalisés dans la maîtrise de la physique et de la détection des neutrinos ouvrent aujourd'hui la porte à la physique appliquée des antineutrinos. Dans cette optique, cette particule a en effet la particularité fondamentale de porter l'information de son lieu d'émission sans perturbation. Comme les neutrinos sont liés aux processus faibles tels que la désintégration nucléaire beta les applications se trouvent dans la surveillance des matières radioactives et des réacteurs nucléaires. Dans ce contexte, le projet Nucifer vise à construire et opérer un détecteur miniature d'antineutrinos de réacteur nucléaire, à installer au maximum à quelques dizaines de mètres d'un réacteur de puissance pour suivre sa puissance thermique et évaluer la quantité de plutonium produite. De plus, une réanalyse récente des mesures précédentes réalisées à proximité de réacteurs ces 40 dernières années montrent un écart significatif entre les taux de détection neutrinos attendus et mesurés. Parmi les hypothèses variées qui permettent d'expliquer cette anomalie se trouve une nouvelle oscillation entre neutrinos, impliquant nécessairement l'existence d'un quatrième neutrino, stérile. Pour mettre en évidence les antineutrinos et mesurer leur énergie, la détection beta inverse dans environ 850 kg de liquide scintillant dopé au gadolinium est utilisée. Toute la difficulté expérimentale provient des bruits de fond, qui peuvent être très importants lorsque le détecteur est installé ) proximité du réacteur ou de la surface. Le détecteur est maintenant intégré sur le réacteur nucléaire de recherche Osiris du CEA, situé à Saclay, et a commencé la prise de données en avril 2012. Malheureusement, une faible longueur d'atténuation du liquide et un niveau de bruit de fond gamma inattendu nous empêchent de distinguer les neutrinos. Nous attendons maintenant le remplacement du liquide et la construction d'un nouveau mur de plomb pour continuer l'étude du suivi du réacteur et pour tester l'hypothèse de neutrino stérile. / The major advances done in the understanding of neutrinos properties and in detector technology have opened the door to a new discipline: the Applied Antineutrino Physics. Indeed, this particle has the great advantage to carry information from its emission place without perturbation. Because neutrinos are inextricably linked to nuclear processes, new applications are in nuclear safeguards. In this context, the Nucifer project aims to test a small electron-antineutrino detector to be installed a few 10 meters from a reactor core for monitoring its thermal power and for testing the sensitivity to the plutonium content. Moreover, recent re-analysis of previous short-distance reactor-neutrino experiments shows a significant discrepancy between measured and expected neutrino count rates. Among the various hypotheses a new phenomenon as the existence of a fourth sterile neutrino can explain this anomaly. To be able to count neutrinos and get the corresponding energy spectrum, the detection is based on the inverse beta decay in about 850 kg of doped liquid scintillator. The experimental challenge is to operate such a small detector in a high background place, due to the closeness with the surface and the reactor radiations. The detector is now finished and data taking has begun at the Osiris research reactor in Saclay since april 2012. Sadly, unexpected low liquid attenuation length and high gamma background level prevented us to highlight neutrinos. We are now waiting for a liquid change and a new lead wall to study reactor monitoring and to test the sterile neutrino hypothesis.

Atualmente existem muitas evidências da presença de matéria escura no Universo. Estas motivaram a existência de vários experimentos para sua detecção. Entre os experimentos de detecção indireta de matéria escura, o PAMELA, o ATIC e o Fermi-LAT observaram recentemente excessos de elétrons e pósitrons no fluxo galáctico em relação ao esperado para estas partículas. Estes resultados podem ser explicados pela aniquilação de matéria escura com massas entorno a 1 TeV em nossa galáxia, com produção de léptons. No entanto, para tal, estas observações requerem um aumento na taxa de aniquilação relativa à esperada da produção térmica de matéria escura. Este aumento pode ser devido a existência de subestruturas de matéria escura no halo galáctico ou a mecanismos de interação, como o efeito Sommerfeld, que aumentam a seção de choque de aniquilação das partículas de matéria escura. Neste _ultimo caso, deve ocorrer também um aumento na taxa de neutrinos provenientes da aniquilação de matéria escura no núcleo da Terra. Neste trabalho, estimamos as taxas destes neutrinos e usamos os resultados finais do AMANDA-II e resultados recentes de IceCube para testar cenários genéricos que contemplam um aumento na seção de choque de aniquilação. Apresentamos os nossos resultados em função da seção de choque de interação da matéria escura com os núcleos multiplicada pela fração da aniquilação das partículas de matéria escura em neutrinos e, também em função de um fator genérico de boost que parametriza o aumento na seção de choque de aniquilação. Encontramos que modelos de matéria escura requerem fatores de boost da ordem O(100) ou mais e que se aniquilam significativamente em neutrinos são excluídos como explicação dos excessos leptônicos medidos. / Currently there are many evidences of the existence of dark matter in the Universe. These led to experimental dark matter searches and, among them, some indirect detection experiments, PAMELA, ATIC and Fermi-LAT, have recently observed excesses in the galactic flux of electrons and positrons relative to the expected flux of these particles. These results could be explained by dark matter, with masses of the order of 1 TeV, annihilating into leptons in our galaxy. However, in order for this to explain the mentioned excesses, it is required that the dark matter annihilation rate is greater than the implied rate assuming the expected dark matter thermal annihilation cross section. This greater rate could be due to the presence of dark matter substructures in the galactic halo or due to interaction mechanisms, such as the Sommerfeld effect, that enhance the dark matter annihilation cross section. In the latter case, an enhancement in the neutrino flux from annihilation of dark matter particles in the Earth nucleus should also occur. In this work, we use the final results of AMANDA-II and recent results of IceCube to probe generic enhancement scenarios. We present results as a function of the dark matternucleon interaction cross section weighted by the branching fraction into neutrinos, and as a function of a generic boost factor, which parametrizes the expected enhancement of the annihilation rate. We find that dark matter models that require boosts factors of O(100) or more and that annihilate mainly into neutrinos are excluded as a explanation for the observed leptonic excesses.

This thesis contains both physics analysis and hardware studies. It consists of two primary sections: the results of a search for heavy Majorana mass neutrinos, using the event signature of same (like) sign charged electron pairs ($e^{\pm} e^{\pm}$ ) and two jets, and the results of studies to upgrade the Hadronic Forward (HF) and Hadronic Endcap (HE) subdetectors in the Compact Muon Solenoid (CMS) detector in response to the high intensity proton-proton collisions generated at the Large Hadron Collider (LHC) at European Organization for Nuclear Research (CERN, Conseil Europ\'{e}en pour la Recherche Nucl\'{e}aire). In this search for Majorana mass neutrinos, same sign dielectron ($e^{\pm} e^{\pm}$) + dijet events in the final state have been considered as a signature for neutrino particles. The analyzed data corresponds to an integrated luminosity of 19.7 fb\textsuperscript{-1} of proton-proton collisions at a center of mass energy of \begin{math}\sqrt{s} = 8\ TeV \end{math}, collected using the CMS detector during the 2012 operation at the LHC. Monte Carlo simulations accounting for the theoretical expectations of the Standard Model (SM) and the detector limitations are used to prototype the experiment and to test proposed analysis steps. No excess of events is observed in the data beyond the expected SM background. Upper limits are set on the mixing element squared, $|{V}_{eN}|^{2}$, of the heavy Majorana neutrino with standard model neutrinos, as a function of Majorana neutrino mass for masses in the range of 40-500 $GeV/c^2$. The detector upgrade search comprises three sections of this thesis. The first section describes the test results of 1785 multianode Hamamatsu R7600U-200-M4 photomultiplier tubes (PMT) in numerous parameters such as gain, dark current, and timing characteristics, which provide insights on the expected performance of the upgraded CMS-HF detector. These PMTs replaced the previous single anode R7525 PMTs because the glass windows of previous PMTs are the source of Cherenkov radiation, which causes a background noise in the experiment. The second section reports characterization results of two types of PMTs in a novel operation mode for Secondary Emission (SE) Ionization Calorimetry, which is a novel technique to measure electromagnetic shower particles in extreme radiation environments. The third section presents the test results of novel scintillating materials for CMS experiment in specific and future particle accelerators in general. These materials are Polyethylene Naphthalate (PEN), Polyethylene Terephthalate (PET), high efficiency mirror (HEM) and quartz plates with various organic and inorganic coating materials such as p-Terphenyl (pTp), Anthracene and Gallium-doped Zinc Oxide (ZnO:Ga). We have investigated them for radiation hardness, light yield, timing characteristics, and scintillation and transmission properties.

Das Antarctic Muon And Neutrino Detector Array (AMANDA) ist ein Cherenkov Detektor, der sich im Gletscher der Antarktis am Südpol befindet. Wir präsentieren die Analyse von Daten, die in den Jahren 2000 bis 2004 gesammelt wurden, die einer effektiven Detektorlaufzeit von 1001 Tagen entsprechen. Die Suche zielt auf den Nachweis von elektomagnetische und hadronische Teilchenschauern, so gennante Kaskaden, die durch Elektron- und Tauneutrinowechselwirkung produziert werden können. Die hadronischen Kaskaden können auch über neutrale Ströme Wechselwirkung von Neutrinos aller Arten produziert werden. Der Kaskadenkanal hat einige Vorteile in der Suche nach einem diffusen Fluss von astrophysikalischen Neutrinos. Durch die gute Energieauflösung des AMANDA Detektors kann man zwischen einem harten astrophysikalische Spektrum und einem weichen atmosphärischen Spektrum unterscheiden. Außerdem ist der atmosphärischen Elektronneutrinos Fluss um eine Gößenordnung kleiner als der atmosphärische Myonneutrinofluss. Der Untergrund von atmosphärischem Myonen aus Luftschauern kann unterdrückt werden, weil diese als Spuren im Detektor erscheinen und leicht zu identifizieren sind. Mit der hohen Untergrundunterdrückung ist es möglich die Analyse über einen Raumwinkel von 4pi für Energien gegen 50 TeV zu erstrecken. Die Anzahl von gefundenen Ereignissen in dieser Analyse stimmt mit der Erwartung von Hintergrundereignissen überein. Deshalb berechnen wir eine obere Grenze für den diffusen Neutrinofluss aller Neutrinoarten, unter der Annahme, dass alle Neutrinoarten im Verhältnis 1:1:1 auftreten. Die obere Grenze für einen Nuetrinofluss im Energiebereich von 40 TeV bis 9 PeV mit einem Spektrum von E-2 ist 3.96x10-7 GeV s-1 sr-1 cm-2 bei einem Konfidenzniveau von 90%. Dies ist momentan die niedrigste Grenze für einen diffusen Neutrinoflüss aller Neutrinoarten. / The Antarctic Muon And Neutrino Detector Array (AMANDA) is a Cherenkov detector deployed in the Antarctic ice cap at the South Pole. We present the analysis of the AMANDA data collected during 1001 effective days of the detector lifetime be tween the years 2000 and 2004. We focus our search on electromagnetic and hadronic cascades which are produced in charged-current interactions of high-energy electron or tau neutrinos and in neutral-current interactions of neutrinos of any flavor. There are several advantages associated with the cascade channel in the search for a "diffuse" flux of astrophysical neutrinos. The AMANDA''s energy resolution allows us to distinguish between a hard astrophysical spectrum and a soft atmospheric spectrum. In addition, the flux of atmospheric electron neutrinos is lower than that of atmospheric muon neutrinos by one order of magnitude, and the background from downward-going atmospheric muons can be suppressed due to their track-like topology. The low background in this channel allows us to attain a 4pi acceptance above energies of about 50 TeV. The number of events observed in this analysis is consistent with the background expectations. Therefore, we calculate an upper limit on the diffuse all-flavor neutrino flux assuming a flavor ratio 1:1:1 at the detection site. A flux of neutrinos with a spectrum falling as E-2 is limited to 3.96x10-7 GeV s-1 sr-1 cm-2 at 90% C.L. for a neutrino energy range spanning from 40 TeV to 9 PeV. This upper limit is currently the most sensitive limit on the diffuse all-flavor astrophysical neutrino flux.