• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 3
  • 2
  • 1
  • 1
  • Tagged with
  • 7
  • 7
  • 3
  • 3
  • 3
  • 3
  • 2
  • 2
  • 2
  • 2
  • 2
  • 2
  • 2
  • 2
  • 2
  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Precision Neutrino Oscillations: Important Considerations for Experiments

Pestes, Rebekah Faith 26 May 2021 (has links)
Currently, we are in an era of neutrino physics in which neutrino oscillation experiments are focusing on doing precision measurements. In this dissertation, we investigate what is important to consider when doing these precise experiments, especially in light of significant unresolved anomalies. We look at four general categories of considerations: systematic uncertainties, fundamental assumptions, parameterization-dependence of interpretations, and Beyond the Standard Model (BSM) scenarios. By performing a simulation using GLoBES, we find that uncertainties in the fine structure of the reactor neutrino spectrum could be vitally important to JUNO, a reactor neutrino experiment being built in China, so a reference spectrum with comparable energy resolution to JUNO is needed in order to alleviate this uncertainty. In addition, we determine that with their fix of the fine structure problem, JUNO can test the existence of a quantum interference term in the oscillation probability. We also reason that the CP-violating phase is very parameterization dependent, and the Jarlskog invariant is better for talking about amounts of CP violation in neutrino oscillations. Finally, we discover that CP-violating neutrino Non-Standard Interactions (NSIs) could already be affecting the outcomes of T2K and NOνA, two accelerator neutrino experiments, and may be why there is a tension in these two data sets. / Doctor of Philosophy / Neutrinos are very weakly interacting, fundamental particles that are extremely plentiful in the universe. There are three known types (or flavors) of neutrinos, and the fact that they change flavors (or oscillate) informs us that their mass is not zero, but no experiments have been able to put a lower bound on the smallest neutrino mass. Now that experiments measuring neutrino oscillations have become more precise and some significant anomalies remain unresolved, there are considerations that have become important to investigate. In this paper, we look at four of these considerations: • Uncertainties in the finer shapes in the energy spectrum of neutrinos coming from a nuclear reactor (Chapter 2): We find that these uncertainties could destroy the ability of the Jiangmen Underground Neutrino Observatory (JUNO) to meet one of its major goals, unless they measured the spectrum at a spot close to the reactor with a really good energy resolution (comparable to that of JUNO). • An assumption about quantum mechanics being the foundation of particles and their interactions (Chapter 3): We determine that by heeding our warning in Chapter 2, JUNO will be able to test the existence of the term in the oscillation probability arising out of quantum interference. • How the neutrino oscillation parameter known as the CP-violating phase is dependent on the parameterization scheme used for the matrix describing how the flavors mix to make neutrino oscillation possible (Chapter 4): We find that the parameterization dependence is drastic, and if we want to discuss how much CP violation (i.e. a measure of how neutrinos behave differently from their anti-matter counterparts) exists in neutrino oscillations, we should talk about a quantity called the Jarlskog invariant. • The possibility of interactions existing between neutrinos and other particles that are not part of the Standard Model of Particle Physics, i.e. neutrino Non-Standard Interactions (NSIs) (Chapter 5): We discover that NSIs that are CP-violating can actually explain a current discrepancy between two neutrino oscillation experiments: Tokai to Kamioka Nuclear Decay Experiment (T2K) and NuMI Off-axis ν e Appearance (NOνA).
2

Matrizes de massa e violação CP / Mass matrices and CP violation

Gaydutschenko, Larissa, 1987- 19 May 2006 (has links)
Orientador: Orlando Luis Goulart Peres / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Física Gleb Wataghin / Made available in DSpace on 2018-08-23T16:45:26Z (GMT). No. of bitstreams: 1 Gaydutschenko_Larissa_M.pdf: 776013 bytes, checksum: dded3e977e716b07101df7cb392a6b94 (MD5) Previous issue date: 2013 / Resumo: O fenômeno de oscilação de neutrinos, já experimentalmente observado, só pode ser explicado se a massa dos neutrinos for diferente de zero. No entanto, até pouco tempo atrás, acreditava-se que neutrinos não tivessem massa. O Modelo Padrão das partículas elementares ainda não é capaz de descrever a natureza massiva dos neutrinos, de forma que as matrizes de mistura para léptons (entre autoestados de gauge e autoestados de massa), análogas às matrizes de mistura de quarks, ainda não podem ser encontradas. Através de uma pequena extensão do Modelo Padrão, é possível descrever uma física que leva em conta essas massas e que, portanto, nos fornece essas matrizes de mistura. Essa extensão trata-se de nada mais que o acréscimo de uma nova partícula ao modelo, um lépton neutro que não interage por força fraca. Essa partícula é chamada de neutrino estéril. Portanto, acrescentando um ou mais neutrinos estéreis ao Modelo Padrão posso obter a matriz de mistura para léptons e, consequentemente, contar o número de parâmetros físicos que ela possui. O interesse em contar esses parâmetros reside no fato de que encontrar o número de fases complexas presentes na matriz de mistura é equivalente a encontrar o número de fases de violação de simetria conjugação de carga e paridade (CP) para léptons. Em 1967, o físico russo Andrei Sakharov propôs uma forma de explicar a assimetria bariônica (matéria-antimatéria) partindo de um estado simétrico. Para isso, algumas condições precisariam ser respeitadas pela física do universo. Uma dessas condições é que exista na natureza uma fonte de violação CP. Procurar essa violação em léptons foi o objetivo deste trabalho. Assim, foi possível obter a matriz de mistura para léptons estendendo o modelo padrão pela adição de um neutrino estéril e levando em conta o caso geral de n famílias de léptons. Uma vez tendo encontrado a matriz de mistura, fizemos a contagem dos parâmetros. Além abranger os cálculos usados para encontrar o número de fases complexas damatriz, a dissertação apresenta uma breve introdução à teoria quântica de campos, a simetrias discretas e ao mecanismo de quebra espontânea de simetria, conceitos necessários para o entendimento do trabalho realizado / Abstract: The neutrino oscillation phenomenum, already experimentally observed, can only be explained if neutrino masses are different from zero. However, till recently, it was believed that neutrinos were massless. The Standard Model of elementary particles is yet not able to describe the massive nature of neutrinos, such that the lepton mixing matrix (between gauge eigenstates and mass eigenstates), analogous to the quark mixing matrix, can still not be found. Through a small extension of the Standard Model, it is possible to describe physics that take into account these masses and, therefore, provides us with these mixing matrices. This extension is nothing but the addition of a new particle, a neutral lepton that does not interact through weak force. This particle is called sterile neutrino. So, by adding one or more sterile neutrinos to the Standard Model, I can get the lepton mixing matrix and consequently count the number of physical parameters that it presents. The interest in counting these parameters resides in the fact that finding the number of complex phases in the mixing matrix is equivalent to finding the number of charge conjugation-parity (CP) violation for leptons. In 1967, the Russian physicist Andrei Sakharov proposed a way to explain the baryonic asymmetry (matter-antimatter) beginning with a symmetric state. For that to work some conditions needed to be respected by the universe physics. One of them is that there must exist in nature a source of CP violation. Looking for that source as the leptonic sector of the particle physics was the goal of this project. And finally it was possible to get the lepton mixing matrix extending the standard model by the addition of one sterile neutrino and taking into account the general case of n lepton families. Once we got the mixing matrix, we counted the physical parameters. Besides presenting all the calculation used for finding the number of complex phases in the matrix, this thesis presents a brief introduction to quantum field theory, discrete symmetries and the spontaneous symmetry breaking mechanism, all of these concepts being necessary for the understanding of the work accomplished / Mestrado / Física / Mestra em Física
3

Analyse en composantes indépendantes avec une matrice de mélange éparse

Billette, Marc-Olivier 06 1900 (has links)
L'analyse en composantes indépendantes (ACI) est une méthode d'analyse statistique qui consiste à exprimer les données observées (mélanges de sources) en une transformation linéaire de variables latentes (sources) supposées non gaussiennes et mutuellement indépendantes. Dans certaines applications, on suppose que les mélanges de sources peuvent être groupés de façon à ce que ceux appartenant au même groupe soient fonction des mêmes sources. Ceci implique que les coefficients de chacune des colonnes de la matrice de mélange peuvent être regroupés selon ces mêmes groupes et que tous les coefficients de certains de ces groupes soient nuls. En d'autres mots, on suppose que la matrice de mélange est éparse par groupe. Cette hypothèse facilite l'interprétation et améliore la précision du modèle d'ACI. Dans cette optique, nous proposons de résoudre le problème d'ACI avec une matrice de mélange éparse par groupe à l'aide d'une méthode basée sur le LASSO par groupe adaptatif, lequel pénalise la norme 1 des groupes de coefficients avec des poids adaptatifs. Dans ce mémoire, nous soulignons l'utilité de notre méthode lors d'applications en imagerie cérébrale, plus précisément en imagerie par résonance magnétique. Lors de simulations, nous illustrons par un exemple l'efficacité de notre méthode à réduire vers zéro les groupes de coefficients non-significatifs au sein de la matrice de mélange. Nous montrons aussi que la précision de la méthode proposée est supérieure à celle de l'estimateur du maximum de la vraisemblance pénalisée par le LASSO adaptatif dans le cas où la matrice de mélange est éparse par groupe. / Independent component analysis (ICA) is a method of statistical analysis where the main goal is to express the observed data (mixtures) in a linear transformation of latent variables (sources) believed to be non-Gaussian and mutually independent. In some applications, the mixtures can be grouped so that the mixtures belonging to the same group are function of the same sources. This implies that the coefficients of each column of the mixing matrix can be grouped according to these same groups and that all the coefficients of some of these groups are zero. In other words, we suppose that the mixing matrix is sparse per group. This assumption facilitates the interpretation and improves the accuracy of the ICA model. In this context, we propose to solve the problem of ICA with a sparse group mixing matrix by a method based on the adaptive group LASSO. The latter penalizes the 1-norm of the groups of coefficients with adaptive weights. In this thesis, we point out the utility of our method in applications in brain imaging, specifically in magnetic resonance imaging. Through simulations, we illustrate with an example the effectiveness of our method to reduce to zero the non-significant groups of coefficients within the mixing matrix. We also show that the accuracy of the proposed method is greater than the one of the maximum likelihood estimator with an adaptive LASSO penalization in the case where the mixing matrix is sparse per group.
4

Analyse en composantes indépendantes avec une matrice de mélange éparse

Billette, Marc-Olivier 06 1900 (has links)
L'analyse en composantes indépendantes (ACI) est une méthode d'analyse statistique qui consiste à exprimer les données observées (mélanges de sources) en une transformation linéaire de variables latentes (sources) supposées non gaussiennes et mutuellement indépendantes. Dans certaines applications, on suppose que les mélanges de sources peuvent être groupés de façon à ce que ceux appartenant au même groupe soient fonction des mêmes sources. Ceci implique que les coefficients de chacune des colonnes de la matrice de mélange peuvent être regroupés selon ces mêmes groupes et que tous les coefficients de certains de ces groupes soient nuls. En d'autres mots, on suppose que la matrice de mélange est éparse par groupe. Cette hypothèse facilite l'interprétation et améliore la précision du modèle d'ACI. Dans cette optique, nous proposons de résoudre le problème d'ACI avec une matrice de mélange éparse par groupe à l'aide d'une méthode basée sur le LASSO par groupe adaptatif, lequel pénalise la norme 1 des groupes de coefficients avec des poids adaptatifs. Dans ce mémoire, nous soulignons l'utilité de notre méthode lors d'applications en imagerie cérébrale, plus précisément en imagerie par résonance magnétique. Lors de simulations, nous illustrons par un exemple l'efficacité de notre méthode à réduire vers zéro les groupes de coefficients non-significatifs au sein de la matrice de mélange. Nous montrons aussi que la précision de la méthode proposée est supérieure à celle de l'estimateur du maximum de la vraisemblance pénalisée par le LASSO adaptatif dans le cas où la matrice de mélange est éparse par groupe. / Independent component analysis (ICA) is a method of statistical analysis where the main goal is to express the observed data (mixtures) in a linear transformation of latent variables (sources) believed to be non-Gaussian and mutually independent. In some applications, the mixtures can be grouped so that the mixtures belonging to the same group are function of the same sources. This implies that the coefficients of each column of the mixing matrix can be grouped according to these same groups and that all the coefficients of some of these groups are zero. In other words, we suppose that the mixing matrix is sparse per group. This assumption facilitates the interpretation and improves the accuracy of the ICA model. In this context, we propose to solve the problem of ICA with a sparse group mixing matrix by a method based on the adaptive group LASSO. The latter penalizes the 1-norm of the groups of coefficients with adaptive weights. In this thesis, we point out the utility of our method in applications in brain imaging, specifically in magnetic resonance imaging. Through simulations, we illustrate with an example the effectiveness of our method to reduce to zero the non-significant groups of coefficients within the mixing matrix. We also show that the accuracy of the proposed method is greater than the one of the maximum likelihood estimator with an adaptive LASSO penalization in the case where the mixing matrix is sparse per group.
5

Constraints on the Fourth-Generation Quark Mixing Matrix from Precision Flavour Observables

Menzel, Andreas 27 February 2017 (has links)
Das Standardmodell einer zusätzlichen sequentiellen Fermiongeneration (SM4) war 2012 auf Basis eines Fits an elektroschwache Präzisionsobservable und die Higgs-Signalstärken mit einer Signifikanz von 5.3 sigma ausgeschlossen worden. Komplementär dazu wurden in der vorliegenden Arbeit Fits des SM4 an eine Kombination eines typischen Satzes von Flavour-Observablen mit den Ergebnissen des zuvor durchgeführten Elektroschwachen Präzisionsfits durchgeführt. Im SM3-Kontext extrahierte Größen wurden gemäß ihrer Bedeutung im SM4 reinterpretiert und die angepassten theoretischen Ausdrücke angegeben. Die resultierenden Einschränkungen der CKM-Matrix des SM4, ihrer potentiell CP-verletzenden Phasen sowie der Masse des up-type-Quarks der 4. Generation t'' werden angegeben. Zum Vergleich des SM4 mit dem SM3 werden die erreichten chi^2-Werte genutzt. chi^2=15.53 im SM4 und 9.56 im SM3 passen fast vollkommen zu einer gleich guten Beschreibung der Experimente durch beide Modelle, wobei das SM3 aber sechs Freiheitsgrade mehr besitzt. Außerdem wurden die Vorhersagen des SM3 und des SM4 für die Dimyon-Ladungsasymmetrie ASL mit experimentellen Werten verglichen. Die Vorhersage des SM3 ist ca. 2 sigma vom experimentellen Wert entfernt, die des SM4 ca. 3 sigma.\par Die Ergebnisse deuten nicht darauf hin, dass die Signifikanz des 2012 erreichten Ausschlusses des SM4 durch die Hinzunahme von Flavour-Observablen zu den damals verwendeten elektroschwachen Präzisionsobservablen und Higgs-Querschnitten bedeutend verringert würde.\par Es konnte jedoch keine genaue quantitative Aussage über die Auswirkungen der Flavourobservablen auf diese Signifikanz getroffen werden, weil das Programm CKMfitter likelihood-ratio-Berechnung nur durchführen kann, wenn sich eines der untersuchten Modelle durch Fixierung von Parametern aus dem anderen ergibt (nested models), was hier nicht der Fall ist. / The Standard Model extended by an additional sequential generation of Dirac fermions (SM4) was excluded with a significance of 5.3 sigma in 2012. This was achieved in a combined fit of the SM4 to Electroweak Precision Observables and signal strengths of the Higgs boson. This thesis complements this excludion by a fit of the SM4 to a typical set of Flavour physics observables and the results of the previously performed Electroweak Precision fit. Quantities extracted in an SM3 framework are reinterpreted in SM4 terms and the adapted theoretical expressions are given. The resultant constraints on the SM4''s CKM matrix, its potentially CP-violating phases and the mass of the new up-type quark t'' are given. To compare the relative performance of the SM4 and the SM3, this work uses the chi^2 values achieved in the fit. The values of 15.53 for the SM4 and 9.56 for the SM4 are almost perfectly consistent with both models describing the experimental data equally well with the SM3 having six degrees of freedom more. The dimuon charge asymmetry ASL was not used as a fit input because the interpretation of its measurement was subject to debate at the time when the fits were produced, but its prediction in the fit was used as an additional test of the SM4. The SM3''s prediction differs from the experimental values by about 2 sigma, and the SM4''s prediction by about 3 sigma. \par In summary, these results do not suggest that any significant reduction of the 5.3 sigma exclusion could be achieved by combining the Electroweak Precision Observables and Higgs inputs with Flavour physics data. However, the exact effect of the Flavour physics input on the significance of the SM4''s exclusion cannot be given at this point because the CKMfitter software is currently not able to perform a statistically stringent likelihood comparison of non-nested models.
6

Mesures précises des demi-vies et rapports d’embranchement pour la décroissance β des noyaux miroir 23Mg et 27Si / Precise measurement of half-lives and branching ratios for the mirror β decay of 23Mg and 27Si

Magron, Cécile 29 September 2016 (has links)
L’étude de la décroissance β est un outil fantastique pour approfondir notreconnaissance de l’interaction faible décrite par le Modèle Standard. Ce modèle et laphysique au-delà peuvent être testés par des mesures précises de paramètres caractérisantces décroissances. Parmi ces tests, la vérification de l’hypothèse de la conservation ducourant vectoriel (CVC) et de l’unitarité de la matrice de mélange des quarks de Cabibbo-Kobayashi-Maskawa (CKM) sont d’un grand intérêt. Pour cela, les paramètres caractérisantles transitions β doivent être déterminés très précisément. Les meilleures précisions ont étéobtenues pour les transitions super-permises de Fermi de type 0+ → 0+. Cependant, il existed’autres types de décroissances pour réaliser ces tests, par exemple, les décroissances βmiroir. À ce jour, elles ne permettent pas d’atteindre les précisions obtenues avec lestransitions de type 0+ → 0+. Pour améliorer cela, de nouvelles mesures très précises desparamètres expérimentaux caractérisant ces transitions, comme la demi-vie et le rapportd’embranchement, sont nécessaires. C’est pourquoi une expérience a été réalisée àl’université de Jyväskylä en Finlande, afin d’étudier la décroissance β des noyaux miroir 23Mget 27Si et de mesurer ces paramètres. Les valeurs des demi-vies obtenues pour ces deuxnoyaux sont respectivement dix fois et sept fois plus précises que les moyennes de lalittérature. La valeur obtenue pour le rapport d’embranchement de 23Mg est trois fois plusprécise que la moyenne de la littérature, celui de 27Si étant déjà connu avec une très grandeprécision (0,02%), n’a pas été déterminé avec une meilleure précision. / Beta decays are a fantastic tool to study the weak interaction described by theStandard Model. This model and the physics beyond can be tested by precisemeasurements of nuclear β decays. Among these tests, the conserved vector current (CVC)hypothesis and the unitarity of the Cabibbo-Kobayashi-Maskawa (CKM) quark-mixing matrixare of great interest. For these, the parameters of β transitions must be precisely determined.The highest precisions have been obtained with superallowed 0+ → 0+ Fermi β decays.However, there are other possibilities to make these tests, for example mirror β decays. Fornow, they do not allow to achieve the precision of the 0+ → 0+ transitions. To improve this,new accurate measurements of experimental parameters characterizing these transitions,such as the half-life and the branching ratio, are needed. For this purpose, an experimenthas been carried out at the University of Jyväskylä to study the mirror β decays of 23Mg and27Si and to measure these parameters. The half-life values obtained for these two nuclei are,respectively, ten times and seven times more precise than the literature averages. The valueof the branching ratio obtained for 23Mg is three times more precise than the literatureaverage; the one of 27Si has not been improved as it is already precisely known (0.02%).
7

Zabezpečení vysokorychlostních komunikačních systémů / Protection of highspeed communication systems

Smékal, David January 2015 (has links)
The diploma thesis deals with 128–bit AES data encryption and its implementation in FPGA network card using VHDL programming language. The theoretical part explains AES encryption and decryption, its individual steps and operating modes. Further was described the VHDL programming language, development environment Vivado, FPGA network card Combo–80G and configurable framework NetCOPE. The practical part is the implementation of AES–128 in VHDL. A simulation was used to eliminate errors, then the synthesis was performed. These steps were made using Vivado software. Last step of practical part was testing of synthesized firmware on COMBO–80G card. Total of 4 projects were implemented in FPGA card. Two of them were AES encryption and decryption with ECB mode and another two describe the encryption and decryption with CBC mode.

Page generated in 0.0915 seconds