31 research outputs found
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
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
Baseline-dependent neutrino oscillations with extra-dimensional shortcuts
In extra-dimensional scenarios oscillations between active and sterile
neutrinos can be governed by a new resonance in the oscillation amplitude. This
resonance results when cancelation occurs between two phase differences, the
usual kinematic one coming from the neutrino mass-squared difference, and a
geometric one coming from the difference in travel times of the sterile
neutrino through the bulk relative to the active neutrino confined to the
brane. In this work we introduce a specific metric for the brane-bulk system,
from which we explicitly derive extra-dimensional geodesics for the sterile
neutrino, and ultimately the oscillation probability of the active-sterile
two-state system. We find that for an asymmetrically-warped metric, the
resonance condition involves both the neutrino energy E and the travel distance
L on the brane. In other words, the resonant energy may be viewed as
baseline-dependent. We show that to a good approximation, the resonance
condition is not on E or on L, but rather on the product LE. The model is rich
in implications, including the possibility of multiple solutions to the
resonance condition, with ramifications for existing data sets, e.g., LSND and
MiniBooNE. Some phenomenology with these brane-bulk resonances is discussed.Comment: 20 pages, 5 figure