780 research outputs found
Three Flavor Neutrino Oscillations in Matter: Flavor Diagonal Potentials, the Adiabatic Basis and the CP phase
We discuss the three neutrino flavor evolution problem with general,
flavor-diagonal, matter potentials and a fully parameterized mixing matrix that
includes CP violation, and derive expressions for the eigenvalues, mixing
angles and phases. We demonstrate that, in the limit that the mu and tau
potentials are equal, the eigenvalues and matter mixing angles theta_12 and
theta_13 are independent of the CP phase, although theta_23 does have CP
dependence. Since we are interested in developing a framework that can be used
for S matrix calculations of neutrino flavor transformation, it is useful to
work in a basis that contains only off-diagonal entries in the Hamiltonian. We
derive the "non-adiabaticity" parameters that appear in the Hamiltonian in this
basis. We then introduce the neutrino S matrix, derive its evolution equation
and the integral solution. We find that this new Hamiltonian, and therefore the
S matrix, in the limit that the mu and tau neutrino potentials are the same, is
independent of both theta_23 and the CP violating phase. In this limit, any CP
violation in the flavor basis can only be introduced via the rotation matrices,
and so effects which derive from the CP phase are then straightforward to
determine. We show explicitly that the electron neutrino and electron
antineutrino survival probability is independent of the CP phase in this limit.
Conversely, if the CP phase is nonzero and mu and tau matter potentials are not
equal, then the electron neutrino survival probability cannot be independent of
the CP phase
Oscillation Effects and Time Variation of the Supernova Neutrino Signal
The neutrinos detected from the next Galactic core-collapse supernova will
contain valuable information on the internal dynamics of the explosion. One
mechanism leading to a temporal evolution of the neutrino signal is the
variation of the induced neutrino flavor mixing driven by changes in the
density profile. With one and two dimensional hydrodynamical simulations we
identify the behavior and properties of prominent features of the explosion.
Using these results we demonstrate the time variation of the neutrino crossing
probabilities due to changes in the MSW neutrino transformations as the star
explodes by using the S-matrix - Monte Carlo - approach to neutrino
propagation. After adopting spectra for the neutrinos emitted from the
proto-neutron star we calculate for a Galactic supernova the evolution of the
positron spectra within a water Cerenkov detector and the ratio of charged
current to neutral current event rates for a heavy water - SNO like - detector
and find that these detector signals are feasible probes of a number of
explosion features
A dynamical collective calculation of supernova neutrino signals
We present the first calculations with three flavors of collective and shock
wave effects for neutrino propagation in core-collapse supernovae using
hydroynamical density profiles and the S matrix formalism. We explore the
interplay between the neutrino-neutrino interaction and the effects of multiple
resonances upon the time signal of positrons in supernova observatories. A
specific signature is found for the inverted hierarchy and a large third
neutrino mixing angle and we predict, in this case, a dearth of lower energy
positrons in Cherenkov detectors midway through the neutrino signal and the
simultaneous revelation of valuable information about the original fluxes. We
show that this feature is also observable with current generation neutrino
detectors at the level of several sigmas.Comment: 4 pages, 5 figure
Stimulated Neutrino Transformation with Sinusoidal Density Profiles
Large amplitude oscillations between the states of a quantum system can be
stimulated by sinusoidal external potentials with frequencies that are similar
to the energy level splitting of the states or a fraction thereof. Situations
when the applied frequency is equal to an integer fraction of the energy level
splittings are known as parametric resonances. We investigate this effect for
neutrinos both analytically and numerically for the case of arbitrary numbers
of neutrino flavors. We look for environments where the effect may be observed
and find that supernova are the one realistic possibility due to the necessity
of both large densities and large amplitude fluctuations. The comparison of
numerical and analytic results of neutrino propagation through a model
supernova reveals it is possible to predict the locations and strengths of the
stimulated transitions that occur.Comment: 14 pages, 6 figure
Monte Carlo Neutrino Oscillations
We demonstrate that the effects of matter upon neutrino propagation may be
recast as the scattering of the initial neutrino wavefunction. Exchanging the
differential, Schrodinger equation for an integral equation for the scattering
matrix S permits a Monte Carlo method for the computation of S that removes
many of the numerical difficulties associated with direct integration
techniques
Submarine channel evolution, terrace development, and preservation of intra-channel thin-bedded turbidites: Mahin and Avon channels, offshore Nigeria
The classical turbidite outcrop at San Clemente, California revisited:An example of sandy submarine channels with asymmetric facies architecture
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