Submitted by Luciana Ferreira (lucgeral@gmail.com) on 2015-10-20T13:03:17Z No. of bitstreams: 2 Tese - Michelle Mesquita de Medeiros - 2015.pdf: 11143375 bytes, checksum: a92992a09fff29dbf23fddec60369e77 (MD5) license_rdf: 23148 bytes, checksum: 9da0b6dfac957114c6a7714714b86306 (MD5) / Approved for entry into archive by Luciana Ferreira (lucgeral@gmail.com) on 2015-10-20T13:05:44Z (GMT) No. of bitstreams: 2 Tese - Michelle Mesquita de Medeiros - 2015.pdf: 11143375 bytes, checksum: a92992a09fff29dbf23fddec60369e77 (MD5) license_rdf: 23148 bytes, checksum: 9da0b6dfac957114c6a7714714b86306 (MD5) / Made available in DSpace on 2015-10-20T13:05:44Z (GMT). No. of bitstreams: 2 Tese - Michelle Mesquita de Medeiros - 2015.pdf: 11143375 bytes, checksum: a92992a09fff29dbf23fddec60369e77 (MD5) license_rdf: 23148 bytes, checksum: 9da0b6dfac957114c6a7714714b86306 (MD5) Previous issue date: 2015-05-07 / The MINOS (Main Injector Neutrino Oscillation Search) and MINOS+ experiments were designed to study neutrino oscillations using a muon neutrino beam which is detected in two different locations, in the Near Detector and in the Far Detector. The distance between the detectors allows the beam neutrinos to oscillate to a different flavor. Therefore, a disappearance of the muon neutrinos from the beam is observed in the Far Detector. The Far Detector has a special apparatus which makes possible the selection of atmospheric neutrinos and antineutrinos. These come from interactions of cosmic rays with the Earth’s atmosphere. Both detectors have a magnetic field, allowing the distiction between neutrinos and antineutrinos interactions. This thesis presents the first combined analysis of data from the MINOS and MINOS+ experiments. We have analyzed the combined neutrino energy spectrum from the complete MINOS beam data and the first, more energetic, MINOS+ beam data. The disappearance of the muon neutrinos was observed and the data has shown to be congruent with the oscillation model. Beyond that, we have measured the atmospheric oscillation parameters of the beam and atmospheric neutrinos and antineutrinos from MINOS combined with the atmospheric neutrinos and antineutrinos from MINOS+. Assuming the same oscillation parameters for both neutrinos and antineutrinos, the best fit is obtained for inverted hierarchy and lower octant with m2 32 = 2:37 10􀀀3 eV2 and sin2 23 = 0:43, and the limits m2 32 = [2,29 - 2,49] 10􀀀3 eV2 (68%) and sin2 23 = 0.36 - 0.66 (90%). These results are the most precise measurement of the neutrinos mass splitting using muon neutrino disappearance data only. / Os experimentos MINOS (Main Injector Neutrino Oscillation Search) e MINOS+ foram projetados para o estudo da oscilação de neutrinos por meio do uso de um feixe de neutrinos muônicos que é detectado em dois diferentes locais, no Near Detector e no Far Detector. A distância entre os dois detectores permite com que os neutrinos do feixe oscilem para outro sabor de neutrino, observando-se um “desaparecimento” de neutrinos muônicos no Far Detector. Além disso, este detector possui aparatos especiais que possibilitam a seleção de neutrinos e antineutrinos atmosféricos, os quais são provenientes das interações de raios cósmicos com a atmosfera terrestre. Ambos detectores possuem um campo magnético que proporciona meios para a distinção das interações de neutrinos e antineutrinos. Esta tese apresenta a primeira análise combinada de dados dos experimentos MINOS e MINOS+. Foi realizada uma análise do espectro de energia dos neutrinos considerando dados completos do feixe do experimento MINOS combinados com os primeiros dados do feixe mais energético do experimento MINOS+. Observou-se o desaparecimento dos neutrinos muônicos do feixe e os dados se mostraram condizentes com o modelo de oscilação. Além disso, realizou-se a medida dos parâmetros de oscilação atmosféricos dos neutrinos empregando-se o modelo de três sabores incluindo efeitos de matéria para dados de neutrinos e antineutrinos atmosféricos e do feixe do MINOS, combinados com os dados de neutrinos e antineutrinos atmosféricos do MINOS+. Assumindo mesmos parâmetros de oscilação para ambos neutrinos e antineutrinos, o melhor ajuste obtido foi para hierarquia invertida e octante inferior em m2 32 = 2;37 10􀀀3 eV2 e sin2 23 = 0;43, com limites m2 32 = [2,29 - 2,49] 10􀀀3 eV2 (68%) e sin2 23 = 0,36 - 0,66 (90%). Estes resultados representam a medida mais precisa já realizada do parâmetro de massa dos neutrinos usando somente dados de desaparecimento de neutrinos muônicos.

This thesis studies neutrino oscillations at the proposed ESSnuSB experiment and the effects of invisible decay, where the neutrino mass states are assumed to be able to decay, on the planned measurements and the physics potential for this experiment to detect neutrino decays. This is accomplished by simulating a combined scenario of neutrino oscillations and invisible neutrino decay. It is found that the ESSnuSB experiment would be able to put a bound on the decay parameter $\tau_3 / m_3 = 2.64 (1.68) \times 10^{-11}$~s/eV for the baseline option $360 (540)$~km at $3\sigma$. Further, the effect of invisible neutrino decay on measurements of CP-violation and the precision measurements of $\delta_{\mathrm{CP}}$ for both baseline options are investigated. The results show that the effect is not significant in any case for CP-violation measurements. A significant difference in the precision measurements of $\delta_{\mathrm{CP}}$ is found only when decay is assumed to exist but is not accounted for in the theoretical model. / Det här arbetet undersöker neutrinooscillationer vid det föreslagna experimentet ESSnuSB och ett nytt scenario med osynligt sönderfall av neutriner, där neutriner antas sönderfalla till partiklar som inte växelverkar. Arbetet undersöker hur väl ESSnuSB experimentet kan skilja en modell med neutrinosönderfall från Standardmodellen för neutriner utan sönderfall och hur experimentets andra tester påverkas av neutrinosönderfall. Studien har genomförts genom att simulera en kombinerad modell av neutrinooscillationer och neutrinosönderfall för ESSnuSB-experimentet. Analysen visar att ESSnuSB-experimentet skulle kunna sätta en $3\sigma$-gräns på sönderfallsparametern $\tau_3 / m_3 = 2.64 (1.68) \times 10^{-11}$~s/eV för baslinjelängden $360 (540)$~km. Vidare så studeras hur neutrinosönderfall påverkar mätningar av CP-symmetribrott och precisionsmätning av parametern $\delta_{\mathrm{CP}}$ för båda baslinjelängderna. Resultaten visar att påverkan av neutrinosönderfall på mätningar av CP-symmetribrott är liten. En signifikant skillnad i precisionsmätning av $\delta_{\mathrm{CP}}$ kan ses enbart då neutrinosönderfall antas sant men inte inkluderas i den teoretiska modellen.

Neutrino oscillations in matter can be studied in different regimes, depending on the energy of the incoming neutrinos and the matter density of the medium. In this thesis we investigate neutrino oscillations in dense matter at very high energy (TeV-PeV range), taking into account the absorption that the neutrinos may undergo in such dense media. This absorption phenomenon is relevant for neutrino telescope measurements of astrophysical neutrinos. We begin with a brief reminder on neutrino oscillations in vacuum and the construction of the PMNS matrix. Then, we proceed with calculations for dense matter. We then explore the accuracy of the resulting effective 2-neutrino mixing formulas. They present a good accuracy for Earth-like densities in our range of energies. We develop the calculations for oscillation probabilities in dense matter with absorption through charged-current inelastic scattering for both the two-neutrino and three-neutrino case. We find that in dense media, astrophysical neutrinos indeed undergoabsorption, which reduces signicantly the fluxes for each flavor, with a resonant absorption of electron-anti-neutrinos around E_{res}\simeq 6.3PeV. We discuss the impact of neutrino absorption in the Earth for neutrino telescopes measurements. We find that solar and lunar shadowing is not problematic for current telescopes but could be a good angular resolution indicator for new telescopes to come. / Neutrinooscillationer i materia kan studeras i olika regimer beroende på inkommande neutrinernas energi och densiteten hos det bakomliggande mediet. I detta examensarbete undersöker vi neutrinooscillationer i gränsen av tät materia och mycket hög energi (TeV-PeV-intervall), och tar hänsyn till den absorption av neutriner som då kan inträffa i sådant materia. Detta absorptionsfenomen är relevant för neutrino-teleskopmätningar av astrofysiska neutriner. Vi börjar med att kort påminna oss om neutrinooscillationer i vakuum och konstruktionen av PMNS-matrisen. Vi försätter sedan med beräkningar av neutrinooscillationer i tät materia. Vi undersöker noggrannheten i resulterande effektiva 2-neutrino-blandningsformlerna. De uppvisar en god noggrannhet i jordlika materieprofiler i vårt intervall av energier. Vi utvecklar beräkningarna av oscillationssannolikheterna i tät materia inklusive absorption genom laddad ström oelastisk spridning i båda två- och tresmaksfallen. Vi finner att astrofysiska neutriner i tät materia absorberas, vilket minskar betydligt flödena för varje smak, med en resonansabsorption av elektron-antineutrino omkring E_res\simeq 6.3PeV. Vi diskuterar sedan effekterna av neutrinoabsorption på jorden för neutrino-teleskopmätningar. Vi finner att sol- och månskuggning är inte problematisk för nuvarande teleskop och kunde vara en bra vinkelupplösningsindikator för kommande teeskop.

[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

Orientador: Prof. Dr. Célio Adrega de Moura Junior / Dissertação (mestrado) - Universidade Federal do ABC, Programa de Pós-Graduação em Física, 2017. / Atualmente esta sendo desenvolvendo um experimento de oscilacao de neutrinos de longa linha de base, o Deep Undergound Neutrino Experiment (DUNE). O DUNE tem como objetivos mensurar fase de violacao CP, descrita pelo parametro CP e determinar a hierarquia de massa e o octante do angulo de mistura 23. Alem disso, o DUNE tambem investigara os neutrinos de supernovas, o decaimento do proton (que pode ser um indicio da unificacao das forcas) e fisica alem do modelo padrao. Neste trabalho, explora-se o potencial e a sensitividade do DUNE para determinar os valores dos parametros que mensuram interacoes de neutrinos nao descritas pelo Modelo Padrao das Particulas Elementares (MP), chamadas de interacoes nao-padrao (NSI). Investiga-se tambem como a distribuicao de materia ao longo da linha de propagacao de neutrinos influencia na determinacao dos parametros de NSI. Para tanto, descreve-se como sao as interacoes de neutrinos com a materia terrestre por interacoes padrao e nao-padrao. Apresentam-se as caracteristicas do DUNE e os dois modelos de densidade de materia para a linha do feixe que foram testados: a gReferencia Preliminar do Modelo da Terrah (PREM) e o modelo descrito por Shen e Ritzwoller (SR). Simula-se o espectro de energia no detector utilizando-se o software General Long Baseline Experiment Simulator (GLoBES). Obtem-se a sensitividade dos parametros de interesse utilizando um metodo de 2 e compara-se a sensitividade para os diferentes modelos de densidade de materia utilizando-se as areas das curvas de sensitividade do espaco de parametros e tambem as amplitudes dos parametros. Os resultados corroboram com a proposta do DUNE em medir os valores de CP e 23 com uma precisao maior que os experimentos atuais, assim como determinar a hierarquia das massas. Como uma nova contribuicao para a colaboracao DUNE, mostrou-se que a mudanca na distribuicao da densidade de materia da linha do feixe causa um desvio de no maximo 1,4 relativo na determinacao do intervalo de valores de CP . Para a determinacao dos intervalos de valores dos parametros de NSI, ha um desvio minimo de 1,4 relativo para a determinacao de "ee e um desvio maximo de 4 relativo na determinacao de |"e¿Ê|. Mostra-se ainda que o DUNE podera restringir os valores dos parametros de NSI para valores menores que 1 para os parametros "ee e " e valores menores que 0,1 para os demais parametros de NSI. / Currently it is being developed an experiment of long baseline neutrino oscillation, the Deep Underground Neutrino Experiment (DUNE). DUNE aims to measure the CP violation phase, described by the parameter CP , determine the mass hierarchy, and the octant of the mixing angle 23. In addition, DUNE will also investigate supernova neutrinos, proton decay (which may be a signal of the unification of forces), and physics beyond the standard model. In this work, we explore the sensitivity of DUNE to determine the values of the parameters that measure neutrino interactions not described by the Standard Model of Elementary Particles (MP), the so called nonstandard interactions (NSI). We also investigate how the distribution of matter along the baseline of neutrino propagation influences the determination of NSI parameters. Therefore, standard and nonstandard neutrino interactions with Earth¿s matter is described. We present the features of DUNE and test two models of matter density along the beam line. These models are the "Preliminary Reference Earth Model" (PREM) and the model described by Shen and Ritzwoller (SR). The energy spectrum is simulated in the detector using the General Long Baseline Experiment Simulator (GLoBES) software. The sensitivity of the parameters of interest are obtained using a method of 2 and the sensitivities for the different matter density models are compared using the allowed regions in the parameter space. The results corroborate with DUNE proposal to measure the values of CP and 23 with greater accuracy than current experiments and determine the mass hierarchy. As a new contribution to the DUNE collaboration, we show that the change in the density distribution of the beam line causes a deviation of at most 1.4 relative in determining the range of values of CP . For determination of the ranges of values of the NSI parameters, there is a minimum deviation of 1.4 relative for the determination of "ee and a maximum deviation of 4 relative in determining |"eì|. We also show that DUNE may restrict the values of the NSI parameters to values less than 1 for the parameters "ee and " , and values less than 0.1 for the other NSI parameters.

[pt] Em física de neutrinos, quase todos os dados de experimentos importantes podem ser explicados através de oscilação de neutrinos causados por massas e misturas. Porem, existe a possibilidade de que os neutrinos tenham algumas propriedades, além dessas mencionadas, que manifesta alguma física nova ou física além do modelo padrão. Esta nova física pode ser explicada por partículas exóticas ainda desconhecidas que são responsáveis por interações extras ou interação não padrão com os neutrinos e aqui as estudaremos fenomenologicamente, isto é, não nos preocuparemos com um modelo teórico em si. Nesta tese, estudamos os efeitos dessa interação não-padrão de neutrinos com a matéria para os experimentos de oscilação de grandes comprimentos. Nós consideramos dois detetores idênticos, mas com suas distâncias em relação à fonte, diferentes em dois casos: Primeiro, estudamos o potencial para sondar os efeitos de interação não-padrão para experimentos que usam feixes de neutrinos convencionais vindo de decaimentos de píons. Como exemplo, consideramos um feixe de neutrinos a ser criado pelo acelerador de prótons do JPARC (Japan Proton Accelerator Research Complex) no Japão. Nele, consideramos dois detetores, além do detetor próximo ao JPARC para monitorar o feixe; temos o primeiro que está situado em Kamioka, Japão e o outro em algum lugar na Coréia do Sul, sendo que o primeiro está a 295 km, enquanto o segundo está em torno de 1000 km do JPARC. Segundo, avaliamos também o potencial da fábrica de neutrinos, o qual utiliza feixes de neutrinos vindo do decaimento de múons armazenados num anel para estudar os parâmetros de interação não-padrão e o seu impacto na sensibilidade da fase de violação CP e o ângulo de mistura 013. Neste trabalho, também combinamos os dados simulados com dois detetores com comprimentos diferentes, sendo o primeiro a 3000 km e o outro a 7000 km da fonte. O comprimento deste segundo detetor foi escolhido pelo fato de ter uma característica peculiar, o Magic Baseline (comprimento mágico), onde a probabilidade de oscilação não depende da fase de violação de CP quando os parâmetros não-padrão estão ausentes. / [en] In neutrino physics, most of the experimental data importants can be explained due to neutrino oscilation induced by mass and mixing. However, there is the posibility that the neutrinos have some properties, new physics or beyond Standard Model. This new physics can be explained with some so far unknown exotic particles that are responsables for extra interactions ornon standard interaction with neutrinos and here we studied fenomenologically, without concerning about any theoretical model. In this Thesis, we study the effects of Non Standard Interaction (NSI) with matter in experimentsof oscilation in long baseline. We consider two identical detectors, but wih diferent baselines from source, in two cases: first, we study the probing potencial to analyse the NSI effect for experiments that use conventionalneutrino beams coming from pions decay. For example, we should consider a neutrino beam created at the Proton Accelerator JPARC (Japan Proton Accelerator Research Complex) in Japan. We consider two detectors, in additionto the front detector at JPARC to monitor the beam; we have the first in Kamioka, Japan and other somewhere in Korea, the first is at 295km, and the second is localizate about 1000 km from JPARC. In sequence, we also evaluate the potencial of Neutrino Factory, where a neutrino beam come from a muon decay storage ring, in order to study the non standard interactions parameter and its impact in CP phase sensibility and the mixingangle 013. In this work we combined theses simulated data from two detectors with differents baselines, with the first localized at 3000 km and the other at 7000 km from the source. The baseline of this second detectorwas chosen because it has a special feature, the Magic Baseline, where theoscilation probability do not depend of CP phase violation when the nonstandard parameters are absent.

Orientador: Marcelo Moraes Guzzo / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Física Gleb Wataghin / Made available in DSpace on 2018-08-24T07:13:46Z (GMT). No. of bitstreams: 1 Costa_RafaelNobertoAlmeidada_M.pdf: 2184656 bytes, checksum: 96104bbac452f3b0ec1bab401b55bf0a (MD5) Previous issue date: 2014 / Resumo: Apresentamos neste trabalho um review descrevendo a oscilações de neutrinos quando é levado em conta a violação da simetria de carga paridade (CP). Por conta disso abordaremos a origem da violação de CP no Modelo Padrão das Partículas Elementares, desde a sua descoberta no sistema dos mésons káons neutros (K°) ,até a sua inclusão dentro do Modelo Padrão, a qual foi desenvolvida por Kobayashi e Maskawa. Depois de entendermos a violação de CP passamos a tratar das oscilações de neutrinos e como esta violação é incluída no modelo. Abordamos o modelo utilizando os dados mais recentes dos parâmetros para as oscilações de neutrinos, incluindo a recente medição do ângulo de mistura ?13. Utilizando estes dados e os resultados obtidos a partir do modelo de oscilações de neutrinos inferimos um limite para a fase de violação de CP, dado por nós como sendo ?CP= 19 ^{+19°}_{-9°} com 1? de C.L. / Abstract: In this work was make a review describing the neutrino oscillations when is taken in account the charge parity symmetry violation (CP). Because of that we will approach the origin of CP violation in Standard Model of Elementary Particles, since its discovery in the neutral kaons meson system (K°), until its inclusion within the Standard Model, made by Kobayashi and Maskawa. After we understand the CP violation we treat the neutrino oscillations and how this violation is included in the model. We approach the model using the most recent data of the parameters from neutrino oscillations, including the recent data measured to the mixing angle ?13. Utilizing this data, and the data obtained from the model of neutrino oscillation, we infer a limit to the CP violation phase, given by us as being ?CP= 19^{+19°}_{-9°} with 1? of C.L. / Mestrado / Física / Mestre em Física

Neutrinooszillationen sind ein sehr aktives Forschungsfeld. In den letzten Jahrzehnten haben viele Experimente das Phänomen untersucht und sind inzwischen zu Präazisionsmessungen vorangeschritten. Mit seiner Niederenergieerweiterung DeepCore kann das IceCube-Experiment zu diesem Forschungsfeld beitragen. IceCube ist ein 1 km^3 großes Tscherenkow-Neutrino-Teleskop, welches das tiefe, antarktische Eis des Südpols als optisches Medium nutzt. DeepCore ist eine Erweiterung mit dichterer Instrumentierung im unteren Teil des IceCube-Teleskops. Diese dichte Instrumentierung ermöglicht den Nachweis von Neutrinos mit Energien ab einer Energieschwelle von etwa 10 GeV. Jedes Jahr werden Tausende von atmosphärischen Neutrinos oberhalb dieser Schwelle in DeepCore detektiert. Eine Bestimmung der Energie der Neutrinos und des durch sie zurückgelegten Weges durch die Erde ermöglicht die Messung von Neutrinooszillationen. In dieser Arbeit werden zunächst die Möglichkeiten von DeepCore diskutiert, Oszillationen auf unterschiedliche Weise zu messen. Das Verschwinden von Myon-Neutrinos wird als erfolgsversprechender Prozess ausgewählt. Darauf folgt die Beschreibung einer Methode zur Identifizierung von Tscherenkow-Photonen, welche detektiert wurden, bevor sie gestreut wurden -sogenannte- direkte Photonen. Mit Hilfe dieser Photonen kann der Zenitwinkel der Myon-Neutrinos bestimmmt werden. Auch die Energie der Neutrinos wird rekonstruiert. In den Jahren 2011 und 2012 wurden innerhalb von 343 Tagen mit dieser Analyse 1487 Neutrinokandidaten mit Energien zwischen 7 GeV und 100 GeV in DeepCore gefunden. Vergleicht man diese Zahl mit der erwarteten Zahl vom atmosphärischen Neutrinofluss ohne Oszillationen, so ergibt sich ein Defizit von etwa 500 Ereignissen. Die Osziallationsparameter, die die Daten am besten beschreiben, sind im Einklang mit den Parametern, die von anderen Experimenten veröffentlicht wurden. / The study of neutrino oscillations is an active field of research. During the last couple of decades many experiments have measured the effects of oscillations, pushing the field from the discovery stage towards an era of precision and deeper understanding of the phenomenon. The IceCube Neutrino Observatory, with its low energy subarray, DeepCore, has the possibility of contributing to this field. IceCube is a 1 km^3 ice Cherenkov neutrino telescope buried deep in the Antarctic glacier. DeepCore, a region of denser instrumentation in the lower center of IceCube, permits the detection of neutrinos with energies as low as 10 GeV. Every year, thousands of atmospheric neutrinos around these energies leave a strong signature in DeepCore. Due to their energy and the distance they travel before being detected, these neutrinos can be used to measure the phenomenon of oscillations. This work starts with a study of the potential of IceCube DeepCore to measure neutrino oscillations in different channels, from which the disappearance of muon neutrinos is chosen to move forward. It continues by describing a novel method for identifying Cherenkov photons that traveled without being scattered until detected direct photons. These photons are used to reconstruct the incoming zenith angle of muon neutrinos. The total energy of the interacting neutrino is also estimated. In data taken in 343 days during 2011-2012, 1487 neutrino candidates with an energy between 7 GeV and 100 GeV are found inside the DeepCore volume. Compared to the expectation from the atmospheric neutrino flux without oscillations, this corresponds to a deficit of about 500 muon neutrino events. The oscillation parameters that describe the data best are in agreement with the results reported by other experiments. The method and tools presented allow DeepCore to reach comparable precision with the current best results of on-going experiments once five years of data are collected.

Neutrinooszillation, ein Phänomen, das den Neutrino-Flavour nach ihrer Ausbreitung durch den Weltraum verändern kann, ist ein Beweis für nicht-verschwindende Neutrinomassen und ein Hinweis auf eine neue Physik außerhalb des Standardmodells. Diese Arbeit präsentiert die erste Messung zu atmosphärischen Neutrinooszillationen, die sechs Jahre zwischen Mai 2011 und Mai 2017 des IceCube DeepCore Experiment umfasst. Sie erweitert die bisher verfügbare Ereignisauswahl um eine neue Ereignissignatur und einen großeren Energiebereich. Diese Arbeit beschreibt die Methoden, die für die Simulationen der Wechselwirkungen der Neutrinos, die Ereignisauswahl, die Rekonstruktion und die statistische Behandlung von Messdaten und systematischen Messunsicherheiten benutzt werden. Die beste Abschätzung für die Neutrino-Mischungsparameter ist $\Delta m^2_{32} = 2.54^{+0.11}_{-0.12}\cdot 10^{-3}$~eV$^2$ und $\sin^2 \theta_{23} = 0.51\pm0.05$ (68\% C.L.) und gehört zurzeit zu den präzisesten Messungen atmosphärischer Neutrinos. Darüber hinaus wird in dieser Arbeit das Standard-Drei-Flavour-Modell überprüft, indem ein steriles Neutrino mit einer Masse in der Größenordnung von 1 eV eingeführt wird. Die Suche nach Effekten steriler Neutrinos auf atmosphärischen Neutrinooszillationen wird auf drei Jahren Daten, genommen zwischen Mai 2011 und Mai 2014, durchgeführt. Die Ergebnisse stimmen mit dem Standard-Modell der Drei-Neutrino-Oszillation überein, was zu den Obergrenzen für sterilen Neutrino-Mischungsparameter $|U_{\mu4}|^2<0.11$ und $|U_{\tau4}|^2<0.15$ (90\% C.L.) für $\Delta m^2_{41}=1$~eV$^2$ führt. Dieser Ergebnis ist derzeit die stringenste Obergrenze für $|U_{\tau4}|^2$. / Neutrino oscillations, a phenomenon that can change the flavour of neutrinos after their propagation through space, are a proof of non-zero neutrino masses and are an indication of new physics beyond the Standard Model. This work presents the first measurement of the atmospheric neutrino oscillations using six years of IceCube DeepCore data taken between May 2011 and May 2017. It extends the previously available event selection to include new event signatures and to use an extended energy range. This work discusses the techniques used for simulation of neutrino interactions, event selection, reconstruction, and the statistical treatment of data and systematic uncertainties. The best estimates for the neutrino mixing parameters are $\Delta m^2_{32} = 2.54^{+0.11}_{-0.12}\cdot 10^{-3}$~eV$^2$ and $\sin^2 \theta_{23} = 0.51\pm0.05$ (68\% C.L.), which are currently among the most precise measurements obtained with atmospheric neutrinos. In addition, this work tests the standard three-flavour paradigm by introducing one sterile neutrino with a mass on the order of 1~eV. The search for sterile neutrino effects in atmospheric neutrino oscillations is performed with three years of data taken between May 2011 and May 2014. The results are consistent with the standard three-neutrino oscillation picture, leading to limits on the allowed sterile neutrino mixing of $|U_{\mu4}|^2<0.11$ and $|U_{\tau4}|^2<0.15$ (90\% C.L.) for $\Delta m^2_{41}=1$~eV$^2$. Currently, the limit for $|U_{\tau4}|^2$ is the most stringent in the World.