Adiabatic & non-adiabatic perturbation theory for coherence vector description of neutrino oscillations

The standard wave function approach for the treatment of neutrino oscillations fails in situations where quantum ensembles at a finite temperature with or without an interacting background plasma are encountered. As a first step to treat such phenomena in a novel way, we propose a unified approach to both adiabatic and non-adiabatic two-flavor oscillations in neutrino ensembles with finite temperature and generic (e.g. matter) potentials. Neglecting effects of ensemble decoherence for now we study the evolution of a neutrino ensemble governed by the associated Quantum Kinetic Equations, which apply to systems with finite temperature. The Quantum Kinetic Equations are solved formally using the Magnus expansion and it is shown that a convenient choice of the quantum mechanical picture (e.g. the interaction picture) reveals suitable parameters to characterize the physics of the underlying system (e.g. an effective oscillation length). It is understood that this method also provides a promising starting point for the treatment of the more general case in which decoherence is taken into account.Comment: 14 page

Neutrino-antineutrino oscillations as a possible solution for the LSND and MiniBooNE anomalies?

We investigate resonance structures in CPT and Lorentz symmetry violating neutrino-antineutrino oscillations in a two generation framework. We work with four non-zero CPT-violating parameters that allow for resonant enhancements in neutrino-antineutrino oscillation phenomena in vacuo which are suitably described in terms of charge conjugation eigenstates of the system. We study the relation between the flavor, charge conjugation and mass eigenbasis of neutrino-antineutrino oscillations and examine the interplay between the available CPT-violating parameter space and possible resonance structures. Eventually we remark on the consequences of such scenarios for neutrino oscillation experiments, namely possible solutions for the LSND and MiniBooNE anomalies.Comment: 14 pages, 3 figure

Explaining LSND and MiniBooNE using altered neutrino dispersion relations

We investigate the possibility to explain the MiniBooNE anomaly by CPT and Lorentz symmetry violating neutrino-antineutrino oscillations in a two generation framework. We work with four non-zero CPT-violating parameters that allow for resonant enhancements in neutrino-antineutrino oscillation phenomena in vacuo which are suitably described in terms of charge conjugation eigenstates of the system. We study the relation between the flavor, charge conjugation and mass eigenbasis of neutrino-antineutrino oscillations and examine the interplay between the available CPT-violating parameter space and possible resonance structures.Comment: 3 pages, 1 figure, Proceedings for Erice 2009 Neutrinos in Cosmology, in Astro-, Particle- and Nuclear Physic

Localization of fermions in different domain wall models

Localization of fermions is studied in different gravitational domain wall models. These are generalizations of the brane-world models considered by Randall and Sundrum, but which also allow gravitational localization. Therefore, they might be considered as possible realistic scenarios for phenomenology.Comment: RevTeX, 6 pages, 10 figure

Ensembles, altered dispersion relations and CPT violation in neutrino oscillations and charged lepton decays

Die vorliegende Dissertation behandelt eine Beschreibung veränderter Dispersionsrelationen und CPT-verletzender Effekte in Neutrinooszillationen und dem Zerfall geladener Leptonen. Solche Phänomene können unter anderem im frühen Universum und in Modellen mit zusätzlichen Raumzeitdimensionen auftreten. Wir entwickeln eine Störungstheorie für den Kohärenzvektorformalismus von Neutrinooszillationen und einen vereinheitlichten Zugang für adiabatische und nichtadiabatische Neutrinooszillationen zwischen zwei Generationen in Neutrinoensembles mit endlicher Temperatur und generischen Potenzialen. Dabei vernachlässigen wir Dekohärenz des Ensembles und lösen die quantenkinetischen Gleichungen. Schließlich wenden wir die Methodik der Störungstheorie auf Neutrinoensembles an, in denen Dekohärenz auftritt. Darüberhinaus entwickeln wir eine nichtadiabatische Störungstheorie für Oszillationen zwischen einer beliebigen Anzahl von Neutrinos und Antineutrinos. Wir beziehen dabei Verletzung der Leptonzahl mit ein und behandeln diese als kleinen Störungsparameter. Es zeigt sich, dass eine kleine Leptonzahlverletzung im Vakuum verstärkt werden kann in Materie, welche die CP-Symmetrie bricht. Wir untersuchen weiterhin den Fall von Oszillationen zwischen zwei Neutrinogenerationen. Schließlich betrachten wir Modifikationen von geladenen schwachen Strömen durch Verletzung der CPT-Symmetrie bei niedrigen Energien. Wir untersuchen Zerfälle von Myonen und Antimyonen und verwenden die Vorhersage für deren unterschiedliche Lebensdauern, um die Größenordnung der CPT-verletzenden Parameter einzuschränken. Weiterhin untersuchen wir die differentiellen Zerfallsraten von Myonen und Antimyonen.This thesis introduces a description of altered dispersion relations and CPT-violating effects in neutrino oscillations and charged lepton decays. Such phenomena can arise, e.g., in the early Universe and models with extra spatial dimensions. We develop a perturbation theory for the coherence vector description of neutrino oscillations and propose a unified approach to adiabatic and nonadiabatic two-flavor oscillations in neutrino ensembles with finite temperature and generic potential terms. We neglect ensemble decoherence and solve the associated quantum kinetic equations. Eventually, we apply the methodology of said perturbation theory to neutrino ensembles in the presence of decohering interactions. Moreover, we develop a nonadiabatic perturbation theory for oscillations involving an arbitrary number of neutrinos and antineutrinos. We include lepton-number violation in the approach and treat it as a small perturbation parameter. We find that small lepton-number violation in vacuo can be enhanced in CP-odd matter and apply the formalism to the twogeneration case. Finally, we investigate low-energy CPT-violating modifications in charged current weak interactions. We analyze muon and antimuon decays and, using the difference in their lifetimes, put bounds on the CPT-violating parameters. We also elaborate on muon and antimuon differential decay rates

CPT-violating effects in muon decay

We consider low-energy CPT-violating modifications in charged current weak interactions and analyze possible ramifications in muon and antimuon decays. We calculate the lifetime of muon and antimuon with these modifications, and from the result, put bounds on the CPT-violating parameters. Moreover, we elaborate on the muon and antimuon decay rate differentials in electron energy and spatial angle, which entail interesting phenomenological consequences presenting new ways to constrain CPT violation in charged lepton decays.Comment: 6 page

Lepton number violating effects in neutrino oscillations

We develop a non-adiabatic perturbation theory for oscillations involving an arbitrary number of neutrino and antineutrino species, including the possibility of lepton number violation which we treat as a small effect. We interpret the physics of such an approach for the one generation case by introducing the notion of adiabaticity for neutrino and antineutrino oscillations in analogy to flavor oscillations. We find that in a CP-odd matter environment a small lepton number violation in vacuo can be enhanced. Eventually, we apply the perturbation theory to the two generation case and work out an example for manifestations of lepton number violation, which can be solved both perturbatively as well as analytically thereby further clarifying the nature of the perturbation expansion.Comment: 11 pages, LaTeX, no figur

Проверка знаний по русскому языку слушателей подготовительного отделения для иностранных граждан (методические указания)

Представлены материалы, которые помогут слушателям подготовительного отделения для иностранных граждан подготовиться к пробному экзамену во время зимней сессии и к выпускному экзамену после окончания ПО