1,627 research outputs found
Four-neutrino oscillation solutions of the atmospheric neutrino anomaly
In the context of neutrino scenarios characterized by four (three active plus
one sterile) neutrino species and by mass spectra with two separated doublets,
we analyze solutions to the atmospheric neutrino anomaly which smoothly
interpolate between \nu_\mu-->\nu_\tau and \nu_\mu-->\nu_s oscillations. We
show that, although the Super-Kamiokande data disfavor the pure \nu_\mu-->\nu_s
channel, they do not exclude its occurrence, with sizable amplitude, in
addition to the \nu_\mu-->\nu_\tau channel. High energy muon data appear to be
crucial in assessing the relative amplitude of active and sterile neutrino
oscillations. It is also qualitatively shown that such atmospheric \nu
solutions are compatible with analogous solutions to the solar neutrino
problem, which involve oscillations of \nu_e in both sterile and active states.Comment: Added references. Accepted for publication in Phys. Rev.
Global analysis of three-flavor neutrino masses and mixings
We present a comprehensive phenomenological analysis of a vast amount of data
from neutrino flavor oscillation and non-oscillation searches, performed within
the standard scenario with three massive and mixed neutrinos, and with
particular attention to subleading effects. The detailed results discussed in
this review represent a state-of-the-art, accurate and up-to-date (as of August
2005) estimate of the three-neutrino mass-mixing parameters.Comment: Final version (including a new Appendix), to be published in
"Progress in Particle and Nuclear Physics". Higher-resolution pdf file and
eps figures can be download from http://www.ba.infn.it/~now2004/PPNP_review
Supernova neutrinos: Strong coupling effects of weak interactions
In core-collapse supernovae, neutrinos and antineutrinos are initially
subject to significant self-interactions induced by weak neutral currents,
which may induce strong-coupling effects on the flavor evolution (collective
transitions). The interpretation of the effects is simplified when self-induced
collective transitions are decoupled from ordinary matter oscillations, as for
the matter density profile that we discuss. In this case, approximate
analytical tools can be used (pendulum analogy, swap of energy spectra). For
inverted neutrino mass hierarchy, the sequence of effects involves:
synchronization, bipolar oscillations, and spectral split. Our simulations
shows that the main features of these regimes are not altered when passing from
simplified (angle-averaged) treatments to full, multi-angle numerical
experiments.Comment: Proceedings of NO-VE 2008, IV International Workshop on "Neutrino
Oscillations in Venice" (Venice, Italy, April 15-18, 2008), edited by M.
Baldo Ceolin (University of Padova publication, Papergraf Editions, Padova,
Italy, 2008), pages 233-24
Drag Reduction over Dolphin Skin via the Pondermotive Forcing of Vortex Filaments
The skin of Tursiops Truncatus is corrugated with small, quasi-periodic
ridges running circumferentially about the torso. These ridges extend into the
turbulent boundary layer and affect the evolution of coherent structures. The
development and evolution of coherent structures over a surface is described by
the formation and dynamics of vortex filaments. The dynamics of these filaments
over a flat, non-ridged surface is determined analytically, as well as through
numerical simulation, and found to agree with the observations of coherent
structures in the turbulent boundary layer. The calculation of the linearized
dynamics of the vortex filament, successful for the dynamics of a filament over
a flat surface, is extended and applied to a vortex filament propagating over a
periodically ridged surface. The surface ridges induce a rapid parametric
forcing of the vortex filament, and alter the filament dynamics significantly.
A consideration of the contribution of vortex filament induced flow to energy
transport indicates that the behavior of the filament induced by the ridges can
directly reduce surface drag by up to 8%. The size, shape, and distribution of
cutaneous ridges for Tursiops Truncatus is found to be optimally configured to
affect the filament dynamics and reduce surface drag for swimming velocities
consistent with observation.Comment: 71 pages, 27 encapsulated figure
Analysis of energy- and time-dependence of supernova shock effects on neutrino crossing probabilities
It has recently been realized that supernova neutrino signals may be affected
by shock propagation over a time interval of a few seconds after bounce. In the
standard three-neutrino oscillation scenario, such effects crucially depend on
the neutrino level crossing probability P_H in the 1-3 sector. By using a
simplified parametrization of the time-dependent supernova radial density
profile, we explicitly show that simple analytical expressions for P_H
accurately reproduce the phase-averaged results of numerical calculations in
the relevant parameter space. Such expressions are then used to study the
structure of P_H as a function of energy and time, with particular attention to
cases involving multiple crossing along the shock profile. Illustrative
applications are given in terms of positron spectra generated by supernova
electron antineutrinos through inverse beta decay.Comment: Major changes both in the text and in the figures in order to include
the effect of a step-like shock front density profile; final version to
appear in Physical Review
Addendum to: Model-dependent and -independent implications of the first Sudbury Neutrino Observatory results
In the light of recent experimental and theoretical improvements, we review
our previous model-independent comparison [hep-ph/0106247] of the
Super-Kamiokande (SK) and Sudbury Neutrino Observatory (SNO) solar neutrino
event rates, including updated values for the ``equalized'' SK datum and for
the reference Standard Solar Model (SSM) B neutrino flux. We find that the
joint SK+SNO evidence for active neutrino flavor transitions is confirmed at
the level of 3.3 standard deviations, independently of possible transitions to
sterile states. Barring sterile neutrinos, we estimate the 3-sigma range for
the B neutrino flux (normalized to SSM) as f_B=0.96 +0.54-0.55.
Accordingly, the 3-sigma range for the energy-averaged nu_e survival
probability is found to be = 0.31 +0.55-0.16, independently of the
functional form of P_ee. An increase of the reference nu_e + d --> p + p + e
cross section by ~3%, as suggested by recent theoretical calculations, would
slightly shift the central values of f_B and of to ~1.00 and ~0.29,
respectively, and would strengthen the model-independent evidence for nu_e
transitions into active states at the level of ~3.6 sigma.Comment: 6 pages + 2 figures. Addendum to hep-ph/010624
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