In the first part of the thesis we explore the sensitivity to sterile neutrinos by using a novel kaon tagging technology: ENUBET, the proposed experiment could decisively test indications from the experiments Neutrino-4 and IceCube. In the second part of the thesis we discuss the current status of sterile neutrino searches at nuclear reactors, we present a study with the optimization of a green field, two baseline reactor experiment with respect to the sensitivity for electron anti-neutrino disappearance in search of a light sterile neutrino at both research and commercial reactors. We find that a total of 5 tons of detectors deployed at a commercial reactor with a closest approach of 25 m can probe the mixing angle sin²2θ down to ∼ 5 × 10⁻³ around ∆m² ∼ 1 eV² . The same detector mass deployed at a research reactor can be sensitive up to ∆m² ∼ 20 − 30 eV² assuming a closest approach of 3 m and excellent energy resolution, such as that projected for TAO. We also find that lithium doping of the reactor could be effective in increasing the sensitivity for higher ∆m² values. / Master of Science / A sterile neutrino is a particle that is not included in the actual content of matter at the fundamental level. Our goal in this thesis was to search for an imprint of this particle at neutrino experiments. We performed numerical simulations using the experimental specification given in the literature to predict what this signal should look like. The importance of searching for this particle arises from indications at neutrino nuclear experiments, if this particle exists, that would imply new physics beyond our actual understanding of the matter content in the universe. The first search was performed at an experimental facility called ENUBET and the second search was performed at nuclear reactors. Testing this elusive particle means we need to determine two parameters from a model. The results of the aforementioned parameter space searches are presented in this thesis. The statistical significance in our findings is not entirely conclusive to either confirm or refute the sterile neutrino. The benefits of studying neutrinos at nuclear reactors is that they are produced in generating electrical power as well as monitoring nuclear weapons.

In this thesis, the question of neutrino mass hierarchy is investigated. For this purpose, possibilities of neutrino mass origin are mentioned and phenomenology of neutrino oscillations within three active neutrino framework is introduced. Using that, it is described what neutrino mass hierarchy is and why it would be good to know it. After that, an overview of approaches to this problem is provided, including outline of the JUNO experiment. The approach based on comparison of mass splitting measured in experiments with reactor antineutrinos and accelerator neutrinos is investigated in great detail. The final part of this thesis is measurement of resistive plate chamber properties, as this type of detector was considered to be used in the JUNO experiment (but eventually other type will be used instead).

Observed disappearance of reactor antineutrinos in the short baseline in Daya Bay can be explained by the phenomenon of neutrino flavour oscillations. The analysis in standard three- neutrino framework provides the best measurement of mixing angle of θ13 and the value of effective mass squared difference ∆m2 ee with comparable precision with other experiments. The unprecedented precision of Daya Bay motivates us to extend our search beyond standard three-neutrino oscillation scheme. It this thesis, we have explored two scenarios of possible physics Beyond Standard Model (BSM). We have tested the fundamental symmetry of the nature by searching for the Lorentz Invariance violation effect within the framework of the Standard-Model Extension (SME). Such an effect could be observed as a deviation from three- neutrino oscillation prediction in the oscillated antineutrino spectrum. Since we have not observed any significant deviation, we have been able to set the limits on the SME parameters. Some of the limits were measured for the first time while some turned out not to be competitive with the measurement of other experiments. We have also performed search for Non-standard Interactions (NSIs) in the Daya Bay. Being forbidden in the Standard Model, these interactions are predicted by BSM theories for which...

NOvA is a two detector long-baseline neutrino oscillation experiment using Fermilab's 700 kW NuMI neutrino beam. It studies the disappearance of muon (anti)neutrinos and the appearance of electron (anti)neutrinos in the beam over a distance of 810 km be- tween the detectors. This thesis presents the latest 2020 update of the NOvA neutrino oscillation analysis within the standard model of three neutrinos mixing. With about +50% new data in NuMI neutrino mode (+22% of the total available data) and nu- merous analysis upgrades compared to the previously reported results, the experiment has made over 4σ-significant observation of electron antineutrino appearance in muon antineutrino beam and constrained the oscillation parameters |∆m2 32|, sin2 θ23 and δCP. The text closely depicts the analysis and all its novelties and changes. A detailed inspec- tion is dedicated to the systematic uncertainties and their estimation and validation. Although statistical uncertainties currently dominate in these measurements, under- standing the major sources of systematic uncertainties and their correlations is vital for both the interpretation and precision of the results and for further improvements of the analysis. 1

[pt] Com o avanço na medida dos parâmetros responsáveis por oscilação de neutrinos, podemos dizer que hoje a física de neutrinos está entrando na era da precisão, o que nos permite explorar cenários além de massas e misturas de três sabores de neutrinos, ou seja, podemos procurar uma nova física que cause algum efeito subdominante, que não pode ser explicado por oscilação usual. Podemos citar a anomalia de antineutrinos de reator e anomalia de Gálio, ambas serão explicadas posteriormente no capítulo 3. Propomos uma solução alternativa para estas duas anomalias, baseado em um cenário com grandes dimensões extras. Exploramos também a capacidade de um experimento com neutrinos ultramonocromáticos produzidos via efeito Mossbauer, de detectar ou vincular alguns cenários de nova física além do modelo padrão. Os cenários que consideramos nesta tese são: neutrinos esteréis, estes sendo a extensão mais simples do modelo de três sabores; o cenário com grandes dimensões espaciais extras; descoerência quântica como física não padrão; e por último e não menos importante o cenário com neutrinos de massa variável. Mostramos também o impacto, se assumimos a existência destes cenários, na determinação dos parâmetros de oscilação Delta m2 31 e Teta 13. / [en] With advances in the measurements of the neutrino oscillation parameters, we can assume that neutrino physics is going to a precision era, as a consequence we can explore new scenarios beyond the standard mass and mixing with three neutrino flavors , that is, we can look for a new physics that affects in a subleading way and that can not be explained by the standard oscillation framework. For instance, the reactor antineutrino and Gallium anomalies, both anomalies will be discussed in chapter 3. We propose an explanation for these anomalies based on a scenario with large extra dimension. We also explore the capability of an experiment with ultramonochromatic neutrinos based on M ossbauer effect detects or constrains some new physics scenarios beyond the standard model. In this thesis we consider: sterile neutrinos, large extra dimensions, non standard quantum decoherence and mass varying neutrinos. We also show the impact on the determination of the standard oscillation parameters delta m2 31 and teta 13 if we assume non standard physics scenarios.

A survey of the theory of neutrino oscillations in dense matter and neutrino backgrounds is presented. We discuss collective neutrino systems using the gyroscopic pendulum analogy and describe the motion that results from self-induced parametric resonances. The effects of dense matter on the flavour oscillations of neutrinos are also detailed. This theory is applied to the case of continuous supernova neutrino spectra and explanations of the spectral swapping behaviour seen in numerical studies are summarized. The results of numerical simulations of supernova oscillations in turbulent supernova backgrounds are presented and discussed. We study the motion of two example supernova neutrino spectra and examine the differences in the dynamics and flavour evolution that results from adding turbulent fluctuations to the supernova matter background. We also investigate the effect that fluctuations in the neutrino density can have on the oscillation behaviour. We find that in general the final neutrino spectra emerging from the inner supernova regions are quite robust to fluctuations in the backgrounds in our model, while the intermediate dynamics can be very strongly altered. Some significant changes in the final spectra are also found to occur when the neutrino background density fluctuations are large. We give a detailed review of the resonant matter effects that determine the survival probabilities of atmospheric muon neutrinos. The differences between various Earth density models are described, and these models are then used to predict the flux of muon-type neutrino events in the Deep Core extension to the IceCube detector. We use recent results from the detector collaboration and build on previous work which considered the sensitivity of the detector to the mass hierarchy, and show that uncertainties in the Earth's density can have a significant influence on the event rates.

Orientador: Marcelo Moraes Guzzo / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Física Gleb Wataghin / Made available in DSpace on 2018-08-20T17:05:52Z (GMT). No. of bitstreams: 1 Oliveira_RobertoLeandroNevesde_D.pdf: 2779754 bytes, checksum: a4305b15e2ab247f07cb3cf74146335f (MD5) Previous issue date: 2012 / Resumo: Nesta tese, estudamos algumas consequências fenomenológicas da introdução do fenômeno de dissipação quântica na fenomenologia de oscilações de neutrinos em duas famílias. Utilizando a abordagem de equação mestra to tipo Lindblad-Kossakowski e o critério de completa positividade, descrevemos diferentes modelos para o sistema de oscilação de neutrinos sujeitos aos efeitos dissipativos causados por considerarmos que estes estão abertos a interagirem com o meio a seu redor. Investigamos como incluir os efeitos dissipativos para oscilação de neutrinos no vacuo e para quando os efeitos causados pelo potencial efetivo de matéria também estão incluídos no modelo de oscilação. Por m, aplicamos a fenomenologia estudada ao experimento MINOS como forma de observar como os efeitos dissipativos se comportam frente aos dados experimentais / Abstract: In this thesis, we study the introduction of the quantum dissipation phenomenon and the phenomenological consequences in the model of neutrino oscillations in two families. Using the Lindblad-Kossakowski master-equation approach and the complete positivity condition, we describe different models for the neutrino oscillation system subject to dissipative effects, that are caused when we consider that neutrinos can interact with the environment around them, forming a open quantum system. We investigate as to include the dissipative e ects in neutrino oscillation in vacuum and when the effects of the efective potential of matter are also included in the model of oscillation. Finally, we apply the phenomenology studied to MINOS experiment as a way to observe the behavior of the dissipative e effects from experimental data / Doutorado / Física / Doutor em Ciências

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[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.

The OPERA experiment is designed to perform first direct observation of $nu_{tau}$ appearance in an almost pure $nu_{mu}$ beam. The OPERA detector is a hybrid set-up which combines a lead/emulsion target with various electronic detectors. It is located in Gran Sasso Laboratory (LNGS), 730 km away from CERN where neutrino beam is produced. A good electron identification in the ECC brick would also allow OPERA to search for $nu_{mu}rightarrownu_{e}$ oscillations. We have studied electron identification in the Emulsion Cloud Chamber (ECC) brick which was exposed to CERN SPS H4 electron beam. Emulsion scanning was performed in LNGS scanning laboratory. FEDRA framework was used for the data analysis. In total, we have found 30 electron showers in the brick. The characteristics of each shower have been studied. The background base-track contamination in the shower was estimated as $20pm 4$. This is mainly due to shower overlap of electrons and passing through cosmic rays.