In recent years, many high precision experiments were carried aiming to improve the accuracy on the measurements of the neutrino oscillation parameters. One of the main source of uncertainty for neutrino oscillation experiments is due to the lack of a comprehensive theoretical description of neutrino-nucleus interactions. The US Deep Underground Neutrino Oscillation Experiments (DUNE) will deploy a series of detectors using Liquid Argon Time Projection Chambers (LArTPCs). A fully consistent parameter-free theoretical neutrino-nucleus scattering model on argon does not exist. The first step towards constructing a nuclear model will be to determine the energy and momentum distribution of protons and neutrons inside the argon nucleus. The JLab E12-14-012 experiment performed at Jefferson Laboratory in Newport News, Virginia, ran in 2017 and will provide such measurements in Argon and Titanium using electron scattering (e,e'p). The data collected by the experiment covers a wide range of energy transfers and also includes several other targets like aluminum and carbon. This Ph.D. thesis will present details of the JLab E12-14-012 experiment, together with first data analysis results of the exclusive (e,e'p) data on Argon and Titanium. / Doctor of Philosophy / Neutrino, a tiny, nearly massless particle was discovered about one hundred years ago. Neutrinos are everywhere around us. If you put your hands under the sunlight, each second, there will be about one billion neutrinos pass through them. As the second most abundant particle in the universe, it is extremely important to study neutrinos as they affect many fundamental aspects of our lives. For examples, neutrinos could help us study the nucleons' structure, and how the matter evolved from one particle to many. Since neutrinos are produced in nuclear fusion processes from the sun and stars, we could also understand the sun and universe better by studying the property of neutrinos. Neutrinos have three flavors, and they could change flavors through neutrino oscillation. Measuring the neutrino oscillation parameters is one of the priority tasks for the physics society. Lots of experiments were carried aiming to enhance the understanding of neutrinos and improve the neutrino oscillation measurements accuracy. The most exciting and famous one is the Deep Underground Neutrino Experiment (DUNE) that will be carried in Fermilab. DUNE is an accelerator based experiment that will use Argon as the neutrino target to study the neutrino oscillation. In order to improve the measurement accuracy of the oscillation parameters for the DUNE, a well defined theoretical model for neutrino interaction on Argon is needed. Thus, the JLab E12-14-012 experiment was performed in Hall A at Jefferson Lab in Newport, News, VA to help people get ready for this through electron scattering. The primary goal of this experiment is to measure the electron-nucleus interaction through (e,e$^\prime$p) reactions and further develop a electron-nucleus model to be used in the future neutrino experiments. This thesis will present an overview of the experimental setup and results from the data analysis.

<p>We describe the measurement of muon neutrino disappearance due to</p><p>neutrino oscillation using the Tokai-2-Kamiokande (T2K) experiment's Run 1-4 (6.57&times;10<super>20</super> POT)</p><p>data set. We analyze the data using the conventional</p><p>Pontecorvo-Maki-Nakagawa-Sakata (PMNS) mixing</p><p>matrix for the three Standard Model neutrinos. The output of the</p><p>analysis is a measurement of the parameters sin<super>2</super>&theta;₂₃, &Delta;m<super>2</super>₃₂ for the normal hierarchy and sin<super>2</super>&theta;₂₃, &Delta;m<super>2</super>₁₃ for</p><p>the inverted hierarchy. The best-fit oscillation</p><p>parameters for the normal hierarchy are found to be</p><p>(sin<super>2</super>&theta;₂₃, &Delta;m<super>2</super>₃₂) = ( 0.514, 2.51&times;10<super>-3</super> eV<super>2</super>/c<super>4</super>}). The 90% 1D confidence interval -- determined for both parameters</p><p>using the Feldman-Cousins procedure -- is for the normal hierarchy</p><p>0.428 < sin<super>2</super>&theta;₂₃ < 0.598 and</p><p>2.34&times;10<super>-3</super> eV<super>2</super>/c<super>4</super> < &Delta;m<super>2</super>₃₂ < 2.68\times10^{-3} eV<super>2</super>/c<super>4</super>. </p><p>For the inverted hierarchy, the best-fit oscillation parameters are</p><p>(sin<super>2</super>&theta;₂₃, &Delta;m<super>2</super>₁₃) = (0.511, 2.48&times;10<super>-3</super> eV<super>2</super>/c<super>4</super>. The 90\% 1D Feldman-Cousins confidence intervals for the inverted hierarchy are 2.31&times;10<super>-3</super> eV<super>2</super>/c<super>4</super> < \Delta m^2_{13} < 2.64&times;10<super>-3</super> eV<super>2</super>/c<super>4</super>.</p> / Dissertation

The T2K experiment is a long-baseline neutrino oscillation experiment, in which a muon neutrino beam is directed over a 295 km baseline from the J-PARC facility to the Super-Kamiokande detector. This allows neutrino oscillation to be studied in two channels: disappearance of &nu;_&mu; and appearance of &nu;_e. The T2K beam can be run either in neutrino or antineutrino configuration, for a neutrino beam which is predominantly composed of &nu;_&mu; or anti -&nu;_&mu; respectively. This thesis presents the first oscillation analysis to combine neutrino-mode and antineutrino-mode data sets, giving the first ever sensitivity to the CP-violating phase &delta;_CP from T2K data alone, as well as the most precise T2K measurement of the other neutrino oscillation parameters. The analysis uses a Markov Chain Monte Carlo method to construct a sample from the Bayesian posterior distribution, from which the oscillation parameters of interest and their uncertainties are estimated. Data samples from the T2K near detector, ND280, are fit simultaneously with data from the far detector in order to reduce the uncertainty in the far-detector prediction. When fitting the T2K data alone, the best-fit oscillation parameter values are sin² &theta;₂₃= 0.519^+0.031<sub style='position: relative; left: -2.8em;'>-0.059</sub>, sin² &theta;₁₃= 0.0257^+0.0106<sub style='position: relative; left: -3.2em;'>-0.0440</sub>, &Delta;m²<sub style='position: relative; left: -0.4em;'>32</sub>= 2.54^+0.12<sub style='position: relative; left: -2em;'>-0.10</sub> x 10^-3eV²,and &delta;_CP=-1.91 rad. The 90&percnt; credible interval for &delta;_CP excludes values around &pi;/2: &delta;_CP &notin; [0.38, 2.60] rad. When fitting the T2K data with a constraint on sin² &theta;₁₃ from measurements by reactor experiments, the best-fit oscillation parameter values are sin² &theta;₂₃= 0.519^+0.061<sub style='position: relative; left: -2.8em;'>-0.029</sub>, sin² &theta;₁₃= ^+0.0014<sub style='position: relative; left: -3.2em;'>-0.0014</sub>, Dm²<sub style='position: relative; left: -0.4em;'>32</sub>= 2.54^+0.12<sub style='position: relative; left: -2em;'>-0.12</sub> x 10^-3eV², and &delta;_CP=-1.72 rad. The 90&percnt; credible interval for &delta;_CP contains values &delta;_CP &isin; [-3.10,-0.17] rad, excluding the CP-conserving values 0 and ± &pi; at 90&percnt; probability.

L'expérience STEREO a été proposé afin de donner une réponse sans ambiguïté àl'idée d'un état de neutrino stérile léger ($Delta m^{2}sim 1eV^{2}$) comme l'origine del'anomalie réacteur des antineutrinos. Le but de l'expérience est de confirmer ou de rejetercette hypothèse en recherchant un patron d'oscillation à courte distance (9-11 m) dans lespectre en énergie des $overline{nu_{e}}$'s émis par le réacteur nucléaire de recherchede l'Institut Laue-Langevin à Grenoble (France). A cet effet, le détecteur estcomposé de 2 tonnes du liquide scintillant dopé au Gd et lu par un réseau detubes photomultiplicateurs, et est segmenté en 6 cellules dans la direction depropagation des antineutrinos. Les $overline{nu_{e}}$'s sont détectés par le processusIBD en observant un signal corrélé dans letemps d'un dépôt d'énergie rapide d'un positron et un signal retardé produitpar la capture d'un neutron. La mesure des petites oscillations deformantle spectre d'énergie des antineutrinos nécessite une bonne résolution en énergieet une excellente connaissance de la réponse du détecteur. Ce manuscrit présenteune étude de simulation détaillée basée sur le logiciel Geant4 STEREO, ce quia permis le développement du système de calibration par sources. Ce système aété conçu pour répondre à toutes les exigences physiques de STEREO: calibrerl'échelle de l'énergie et de l'efficacité de capture de neutrons au niveau de 2%,connaître la réponse en énergie dans le spectre d'énergie réacteur antineutrino(1-8 MeV), étudier et la caractériser la réponse et des non-uniformités dudétecteur. A cet effet, on propose un système de calibration consistant en trois sous-systèmes:un sous-système automatisé pour déplacer des sources radioactives autour dudétecteur pour calibrer l'échelle en énergie dans chaque cellule de manièreindépendante. Un second sous-système pour déplacer une source AmBe sous ledétecteur, dont l'objectif est d'inter-calibrerl'efficacité de capture de neutrons entre les cellules. Enfin, un troisième systèmemanuel qui consistent en trois tubes de calibration placés à l'intérieur du liquidescintillante pour évaluer l'efficacité absolue de la capture des neutrons danstrois cellules différentes. La dernièrepartie de ce manuscrit est consacré à l'étude et la caractérisation du bruite de fond gammaet les signaux neutrino attendus. / The STEREO experiment has been proposed to give an unambiguous responseto the hypothesis of a light sterile neutrino state ($Delta m^{2}sim 1 eV^{2}$)as the origin of the reactor antineutrino anomaly. Its goal is to confirm or reject thishypothesis by searching at short distance (9-11 m) for a neutrino oscillation patternin the energy spectrum of the $overline{nu_{e}}$’s emitted by the research nuclear reactorof the Laue-Langevin Institute in Grenoble (France). To this end, the detector iscomposed of 2 tons of Gd-loaded liquid scintillator read out by an array of PMTs, andis segmented in 6 cells in the direction of the $overline{nu_{e}}$’s propagation. Antineutrinosare detected via the IBD process by observing a time correlatedsignal composed of a prompt energy deposit from a positron and a delayed signal produced bythe neutron capture. Measuring small oscillations superimposed on the reactor antineutrinoenergy spectrum requires a good energy resolution and an excellent knowledge ofthe detector response. This manuscript presents a dedicated Geant4 simulation studyof a calibration system based on radioactive sources.This system has been conceived to fulfill all the STEREO physics requirements:calibrating the energy scale and the neutron capture efficiency at the 2 % level,knowing the energy response in the reactor antineutrino energy spectrum (0-8 MeV),and characterizing the detector response in a broader sense (non-uniformities, non-linearity,particle identification, etc). To this end, we proposethree calibration subsystems: one automated subsystem to moveradioactive sources around the detector, whose main role is to calibrate the energy scale in each cellindependently; a second subsystem to inter-calibrate the neutron captureefficiency between cells by moving an AmBe source under the detector; and finally,a third subsystem consisting in three manualcalibration tubes inside the liquid scintillator, necessary to assess the absolute neutron captureefficiency inside three different cells. The final part of this manuscript is devoted tothe study of the selection criteria, and the proposal of methods to reject the expected gammabackground.

京都大学 / 新制・課程博士 / 博士(理学) / 甲第24962号 / 理博第4987号 / 新制||理||1712(附属図書館) / 京都大学大学院理学研究科物理学・宇宙物理学専攻 / (主査)教授 中家 剛, 教授 永江 知文, 教授 田島 治 / 学位規則第4条第1項該当 / Doctor of Science / Kyoto University / DFAM

This thesis is devoted to the theory and phenomenology of neutrino physics. While the standard model of particle physics has been extremely successful, it fails to account for massive neutrinos, which are necessary to describe the observations of neutrino oscillations made by several different experiments. Thus, neutrino physics is a possible window for exploring the physics beyond the standard model, making it both interesting and important for our fundamental understanding of Nature. Throughout this thesis, we will discuss different aspects of neutrino physics, ranging from taking all three types of neutrinos into account in neutrino oscillation experiments to exploring the possibilities of neutrino mass models to produce a viable source of the baryon asymmetry of the Universe. The emphasis of the thesis is on neutrino oscillations which, given their implication of neutrino masses, is a phenomenon where other results that are not describable in the standard model could be found, such as new interactions between neutrinos and fermions. / QC 20100630

[pt] Nesse trabalho realizamos, em princípio, um estudo fenomenológico de alguns experimentos prévios com neutrinos, que utilizaram reatores nucleares como fonte. Tais experimentos buscaram evidências de distorção espectral que corroborassem o mecanismo de conversão de sabor entre neutrinos. Nessa etapa reunimos suficiente informação sobre a metodologia empregada para a detecção e análise do espectro de neutrinos de reatores, bem como os limites impostos por esses experimentos sobre os parâmetros de oscilação. A partir desse estudo, investigamos a possibilidade de se explorar uma região do espaço de parâmetros, caracterizada por um pequeno ângulo de mistura e elevado autoestado de massa, ainda não excluída pelos resultados experimentais atuais. Como uma escala de massa tão elevada não pode estar associada a qualquer um dos três sabores ativos (eletrônico, muônico ou tauônico), em nossa análise, utilizamos uma extensão do modelo de três neutrinos ativos, incorporando um quarto autoestado estéril. Por fim, discutimos uma configuração experimental, baseada em um reator nuclear, que apresente a sensibilidade necessária para atingir esse conjunto de parâmetros. / [en] In this dissertation we have done, at first, a phenomenological study of some previous neutrino experiments, that had searched evidences of spectral distortion that corroborated the mechanism of flavor conversion, using nuclear reactors as source. We collected enough information about the methodology used for detection and analisys of neutrino spectrum of reactors, as well as the constraints on oscillation parameters provided by that experiments. Starting from this study, we investigated the possibility to explore a region of the space of parameters, characterized by a small mixing angle and high mass eigenstate, that not yet have been excluded by experimental results, but incompatible with the extracted current mass scale of the experiments with solar, atmospheric, accelerator (except for the LSND experiment) and reactor neutrinos. For this inquiry, we assume the simplest extension of the standart oscillation model, incorporating a new eigenstate responsible for the higher scale mass. Finally, we discuss a experimental configuration, based on nuclear reactor, which presents the sensitivity required to reach this set of parameters.

The existence of at or curved extra spatial dimensions provides new insights into several of the problems which face the Standard Model of particle physics, including the gauge hierarchy problem, the smallness of neutrino masses, and the dark matter problem. However, higher-dimensional gauge theories are not renormalizable and can only be considered as low-energy effective theories, with limited applicability. Dimensional deconstruction provides a class of manifestly gauge invariant possible ultraviolet completions of higher-dimensional gauge theories, formulated within conventional quantum eld theory. In dimensional deconstruction, the fundamental theory is a four-dimensional quantum eld theory and extra spatial dimensions are generated dynamically at low energies. In this thesis, we study di erent applications of dimensional deconstruction in the contexts of neutrino masses, mixing and oscillations, Kaluza{Klein dark matter, and e ective eld theories for discretized higher-dimensional gravity. A different possibility to understand the smallness of neutrino masses is provided by the see-saw mechanism. This is a genuinely four-dimensional mechanism, where the light neutrino masses are induced by the addition of heavy right-handed Majorana neutrinos or by other heavy degrees of freedom, such as scalar SU(2)L triplet elds. It has the attractive feature of simultaneously providing a mechanism for generating the observed baryon asymmetry of the Universe. We study in this context a specific left-right symmetric see-saw model. / QC 20100716

La recherche de neutrinos stériles et légers est, à l’heure actuelle, l’un des enjeux majeurs de laphysique des neutrinos. Une indication de leur existence résulte de l’anomalie des antineutrinosde réacteur, qui découle du déficit de 6% entre les taux prédits et les taux observéspar les expériences à courte distance de réacteurs. Ce déficit peut être interprété comme uneoscillation à courte distance des neutrinos. L’objectif de l’expérience STEREO, situé auprès duréacteur de recherche de l’Institut Laue Langevin (ILL), à Grenoble, France, est d’étudier cetteoscillation. La cible du détecteur de neutrinos est placée entre 8,9 et 11,1m du coeur compactdu réacteur d’ILL. Le détecteur consiste d’environ 2t d’un scintillateur liquide, dopé avec duGd. Le volume actif est séparé dans le sens de la longueur en six cellules. Les antineutrinos sontdétectés par la désintégration bêta inverse, où ils interagissent avec un proton libre (ion H+) etproduisent un positron et un neutron. Les deux particules sont détectées dans le scintillateurpar une coïncidence retardée où le positron crée un signal prompt et le neutron est capturéaprès un temps de modération. La lumière produite par le scintillateur est mesurée par lesphotomultiplicateurs (PM). Le détecteur est complété par un“gamma catcher” qui entoure la cible et par un veto à muons.Ce manuscrit présente des études concernant la préparation et la mise en exploitation del’expérience STEREO. La conception du blindage magnétique des PM a été menée sur la basede simulations par éléments finis afin d’examiner différentes options, d’étudier en détail lesperformances de l’option retenue ainsi que de déterminer la qualité nécessaire des matériauxutilisés. Sur la base de ces études, la collaboration a retenu un plan de blindage en deuxcouches: une couche de fer doux à l’extérieur, couvrant le détecteur et le veto à muons, et unecouche de mu-métal autour de la cible. Ce blindage réduit les champs magnétiques externes à laposition des PM de la cible à moins de 60μT pour toutes les configurations connues de champsexternes. Ceci réduit à moins de 2% une variation de l’amplification des PM induite par deschangements des champs magnétiques.D’autre part, des études du bruit de fond sur le site de STEREO ont été menées. Unecartographie du bruit de fond du rayonnement gamma a été effectuée avec des détecteurs augermanium et un scintillateur NaI, afin de valider l’efficacité du blindage installé. Uneestimation du taux de bruit de fond est présentée et comparée au taux mesuré avec STEREO.Dans l’état actuel de l’analyse des données, le bruit de fond de coïncidences fortuites est inférieurau bruit de fond corrélé induit par les muons cosmiques. Après une première phase d’exploitationde STEREO, un “doigt de gant” en fin de vie situé à l’avant de STEREO a dû être retiré.Un bouchon était adapté à l’extrémité de ce doigt de gant afin de réduire le bruit du fondpour STEREO. Ce dispositif n’ayant pas pu être réinstallé à la suite l’enlèvement du doigt degant, un nouveau blindage a été proposé par l’ILL. Une série des simulations neutroniques etphotoniques (MCNP) a été effectué pour étudier l’effet de ce changement sur le bruit de fondautour de STEREO et pour décider si le blindage proposé était suffisant. Les deux scénariosavant et après l’enlèvement ont été comparés et selon cette simulation, la situation du bruit defond devrait être améliorée.Enfin une procédure a été proposée et appliquée pour analyser les données de calibration del’échelle d’énergie de STEREO. La procédure a été élaborée pour être applicable pour toutes lessources de calibration disponibles et pour minimiser les incertitudes systématiques. Le résultatpeut être utilisé pour ajuster les paramètres de la simulation Geant4 du détecteur développée parla collaboration, par comparaison avec des données mesurées et après pour déterminer l’échellede l’énergie avec la précision requise de < 2%. / Light sterile neutrinos are currently a topic actively discussed in neutrino physics. Oneindication of their possible existence and their participation in neutrino oscillations is the ReactorAntineutrino Anomaly, which states a deficit of about 6% between predicted and observedantineutrino fluxes in short baseline reactor neutrino experiments. The STEREO experimentaddresses this anomaly by searching for neutrino oscillations at baselines of 8.9-11.1m from thecompact core of the research reactor of the Institut Laue Langevin (ILL), Grenoble, France. Forthis purpose a Gd-loaded liquid scintillator detector was designed with an active target massof about 2 t. The target volume is subdivided in six optically separated cells along the line ofpropagation of the neutrinos. The electron antineutrinos emitted from the reactor are detectedvia the inverse beta decay on hydrogen nuclei, where a positron and a neutron are created. Thesetwo particles are detected in the scintillator in delayed coincidence, with the prompt signal fromthe positron and a delayed signal from neutron capture. The scintillation light created in theprocesses is read out by photomultiplier tubes (PMTs) on top of the detector cells. The detectoris completed by a gamma catcher and a muon veto.This manuscript covers parts of the preparation and the commissioning of the STEREOexperiment. As basis for the design process of the magnetic shielding for STEREO’s PMTsa series of finite element simulations was performed. The studies of different general layoutsand required material qualities as well as of details of the final design are summarised. Underconsideration of these studies the collaboration opted for a shielding design, a double layer setupwith an outer soft iron and inner mumetal layer, which has the required shielding efficiency toreduce the magnetic field at the position of the detector PMTs below 60 μT for all known externalmagnetic field configurations. This limits the maximum PMT gain change due to variations ofthe external magnetic fields to < 2%.Furthermore different studies have been performed concerning the on-site background situation.A mapping of the-ray background was conducted with high purity germanium detectorsand a NaI scintillator detector, in order to validate the efficiency of the installed shielding. Thefocus lied on the characterisation of the count rate in the neutron capture energy window. Anestimation of the background rate is presented and compared to the rate obtained in STEREO.At the current state of the analysis the background of accidental coincidences in STEREO is aminor contribution compared to the muon induced correlated background. In addition a seriesof MCNP simulations was performed to determine the impact of a beamtube removal in thevicinity of STEREO on the overall reactor-related background situation. The beamtube wasclosed by a dedicated shielding, optimised for background reduction for STEREO, which couldnot be reinstalled after removal of the tube. A new shielding at the end of the former beamtubewas proposed by the ILL. Its shielding effect was studied with MCNP and compared tothe previous configuration in order to assess whether the new shielding suffices or needs to beimproved. According to these simulations the background situation is expected to improve.Finally a procedure is proposed and applied for the analysis of the energy calibration ofthe STEREO detector. The procedure is designed to be applicable to all available calibrationsources and to minimise systematic uncertainties. It can be used to adjust parameters in theexisting Geant4-based simulation of the detector, developed by the collaboration, by comparisonto measured data and later to determine the energy scale with the required precision of < 2%.

published_or_final_version / abstract / Physics / Master / Master of Philosophy