941 research outputs found
Comments on Neutrino Tests of Special Relativity
We point out that the assumption of Lorentz noninvariance examined recently
by Coleman and Glashow leads to neutrino flavor oscillations which are
phenomenologically equivalent to those obtained by assuming the neutrinos
violate the principle of equivalence. We then comment on the limits on Lorentz
noninvariance which can be derived from solar, atmospheric, and accelerator
neutrino experiments.Comment: 5 pages, Revte
Is the solar neutrino deficit energy-dependent?
All existing measurements of the solar neutrino flux are compared with the
predictions of the most recent solar model by Bahcall and Pinsonneault,
modified by introducing the hypothesis of neutrino oscillations with mass
differences large enough to render energy-independent any quantity observable
on earth. It is concluded that the data are consistent with this hypothesis and
that, at least for the time being, any energy-dependence of the solar neutrino
deficit must be regarded as just an attractive theoretical possibility, but not
as a compelling reality.Comment: 6 pages, 1 figure, contributed paper to the XVIII Int. Symposium on
Lepton-Photon Interactions, Hamburgh, Germany, 28 July - 1 August 199
Neutrino Oscillations from Strings and Other Funny Things
I will discuss three related unconventional ways to generate neutrino
oscillations (1)Equivalence principle violation by the string dilaton field
(i2)Violation of Lorentz Invariance and (3) Equivalence principle violation
through a non-universal tensor neutrino-gravity coupling. These unorthodox
neutrino oscillation mechanisms are shown to be viable at the level of our
present experimental knowledge and demonstrate that neutrino oscillations can
probe very profound questions
Non-adiabatic level crossing in (non-) resonant neutrino oscillations
We study neutrino oscillations and the level-crossing probability
P_{LZ}=\exp(-\gamma_n\F_n\pi/2) in power-law like potential profiles
. After showing that the resonance point coincides only for a
linear profile with the point of maximal violation of adiabaticity, we point
out that the ``adiabaticity'' parameter can be calculated at an
arbitrary point if the correction function \F_n is rescaled appropriately. We
present a new representation for the level-crossing probability,
P_{LZ}=\exp(-\kappa_n\G_n), which allows a simple numerical evaluation of
in both the resonant and non-resonant cases and where \G_n contains
the full dependence of on the mixing angle . As an application
we consider the case important for oscillations of supernova neutrinos.Comment: 4 pages, revtex, 3 eps figure
Constraining properties of neutron stars with heavy-ion reactions in terrestrial laboratories
Heavy-ion reactions provide a unique means to investigate the equation of
state (EOS) of neutron-rich nuclear matter, especially the density dependence
of the nuclear symmetry energy . The latter plays an important
role in understanding many key issues in both nuclear physics and astrophysics.
Recent analyses of heavy-ion reactions have already put a stringent constraint
on the around the saturation density. This subsequently allowed
us to constrain significantly the radii and cooling mechanisms of neutron stars
as well as the possible changing rate of the gravitational constant G.Comment: 6 pages. Talk given at the Nuclear Physics in Astrophysics III,
Dresden, Germany, March 26-31, 2007. To appear in a special volume of J. of
Phys.
Anomalous diffusion modifies solar neutrino fluxes
Density and temperature conditions in the solar core suggest that the
microscopic diffusion of electrons and ions could be nonstandard:
Diffusion and friction coefficients are energy dependent, collisions are not
two-body processes and retain memory beyond the single scattering event.
A direct consequence of nonstandard diffusion is that the equilibrium energy
distribution of particles departs from the Maxwellian one (tails goes to zero
more slowly or faster than exponentially) modifying the reaction rates.
This effect is qualitatively different from temperature and/or composition
modification: Small changes in the number of particles in the distribution
tails can strongly modify the rates without affecting bulk properties, such as
the sound speed or hydrostatic equilibrium, which depend on the mean values
from the distribution.
This mechanism can considerably increase the range of predictions for the
neutrino fluxes allowed by the current experimental values (cross sections and
solar properties) and can be used to reduce the discrepancy between these
predictions and the solar neutrino experiments.Comment: 16 pages, ReVTeX, no figures. Text partially revised (24 april 1998
A Study of the Day - Night Effect for the Super - Kamiokande Detector: I. Time Averaged Solar Neutrino Survival Probability
This is the first of two articles aimed at providing comprehensive
predictions for the day-night (D-N) effect for the Super-Kamiokande detector in
the case of the MSW \nu_e \to \numt transition solution of the solar neutrino
problem. The one-year averaged probability of survival of the solar \nue
crossing the Earth mantle, the core, the inner 2/3 of the core, and the (core +
mantle) is calculated with high precision (better than 1%) using the elliptical
orbit approximation (EOA) to describe the Earth motion around the Sun. Results
for the survival probability in the indicated cases are obtained for a large
set of values of the MSW transition parameters and
from the ``conservative'' regions of the MSW solution,
derived by taking into account possible relatively large uncertainties in the
values of the B and Be neutrino fluxes. Our results show that the
one-year averaged D-N asymmetry in the survival probability for
neutrinos crossing the Earth core can be, in the case of , larger than the asymmetry in the probability for (only mantle
crossing + core crossing) neutrinos by a factor of up to six. The enhancement
is larger in the case of neutrinos crossing the inner 2/3 of the core. This
indicates that the Super-Kamiokande experiment might be able to test the
region of the MSW solution of the solar neutrino
problem by performing selective D-N asymmetry measurements.Comment: LaTeX2e - 18 Text Pages + 21 figures = 39 Pages. - Figures in PS +
text file sk1b14.tex requires two auxiliary files (included
The sign of the day-night asymmetry for solar neutrinos
A qualitative understanding of the day-night asymmetry for solar neutrinos is
provided. The greater night flux in nu_e is seen to be a consequence of the
fact that the matter effect in the sun and that in the earth have the same
sign. It is shown in the adiabatic approximation for the sun that for all
values of the mixing angle theta_V between 0 and pi/2, the night flux of
neutrinos is greater than the day flux. Only for small values of theta_V where
the adiabatic approximation badly fails does the sign of the day-night
asymmetry reverse.Comment: 3 pages, 3 figures, typos corrected and references adde
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