2,547 research outputs found
Direct determination of the solar neutrino fluxes from solar neutrino data
We determine the solar neutrino fluxes from a global analysis of the solar
and terrestrial neutrino data in the framework of three-neutrino mixing. Using
a Bayesian approach we reconstruct the posterior probability distribution
function for the eight normalization parameters of the solar neutrino fluxes
plus the relevant masses and mixing, with and without imposing the luminosity
constraint. This is done by means of a Markov Chain Monte Carlo employing the
Metropolis-Hastings algorithm. We also describe how these results can be
applied to test the predictions of the Standard Solar Models. Our results show
that, at present, both models with low and high metallicity can describe the
data with good statistical agreement.Comment: 24 pages, 1 table, 7 figures. Acknowledgments correcte
Electron-neutrino survival probability from solar-neutrino data
With SNO data on electron-neutrino flux from the sun, it is possible to
derive the survival probability from existing experimental
data of Super-Kamiokande, gallium experiments and Homestake. The combined data
of SNO and Super-Kamiokande provide boron flux and the total flux of
all active boron neutrinos, giving thus for boron neutrinos. The
Homestake detector, after subtraction of the signal from boron neutrinos, gives
the flux of Be+CNO neutrinos, and for the corresponding energy
interval, if the produced flux is taken from the Standard Solar Model (SSM).
Gallium detectors, GALLEX, SAGE and GNO, detect additionally pp-neutrinos. The
pp-flux can be calculated subtracting from the gallium signal the rate due to
boron, beryllium and CNO neutrinos. The ratio of the measured -neutrino
flux to that predicted by the SSM gives the survival probability for
-neutrinos. Comparison with theoretical survival probabilities shows that
the best (among known models) fit is given by LMA and LOW solutions.Comment: 9 pages, 3 figures, references adde
Investigation of galactic alignment in LSC galaxy clusters
We investigate the galactic axes orientations within 18 selected clusters,
sub-structures of the Local Supercluster. For every cluster we map the
parameter \Delta_{11} (Flin & God{\l}owski 1986) describing the galactic axes
alignment with respect to a cluster pole changing along the entire celestial
sphere. The resulting maps are analyzed for correlations of its maxima with
directions from the cluster centre to 1.) the derived `physical' cluster poles,
2.) the Local Supercluster centre, 3.) the Virgo A centre and 4.) the Earth,
i.e. along the line of sight (LOS). The strong maxima - with one exception -
exist only for non-spiral (NS) sub-samples, with the maximum well correlated
with the LOS direction. For clusters with a clearly defined weak maximum the
conclusion generally does not change. For the spiral (S) sub-samples the maps
are usually at the random noise level. In these cases a weaker, but still
existent correlation with the LOS is observed and no other evident correlations
are noted. We conclude that the strong systematic effect, generated by the
process of galactic axis de-projection from its optical image, is present in
the catalogue data. With the use of a simple model for the systematic effect we
are able to reproduce the main characteristic features of the maps for NS
galaxies. We note, however, a few clusters showing significant differences with
respect to this model.Comment: LaTeX (21 pages, 10 gif figures); MNRAS, accepte
How many sigmas is the solar neutrino effect?
The minimal standard electroweak model can be tested by allowing all the
solar neutrino fluxes, with undistorted energy spectra, to be free parameters
in fitting the measured solar neutrino event rates, subject only to the
condition that the total observed luminosity of the sun is produced by nuclear
fusion. The rates of the five experiments prior to SNO (chlorine, Kamiokande,
SAGE, GALLEX, Super-Kamiokande) cannot be fit by an arbitrary choice of
undistorted neutrino fluxes at the level of 2.5 sigma (formally 99% C.L.).
Considering just SNO and Super-Kamiokande, the discrepancy is at the 3.3 sigma
level(10^{-3} C.L.). If all six experiments are fit simultaneously, the formal
discrepancy increases to 4 sigma (7*10^{-5} C.L.). If the relative scaling in
temperature of the nuclear reactions that produce 7Be and 8B neutrinos is taken
into account, the formal discrepancy is at the 7.4 sigma level.Comment: 1 figure; related information at http://www.sns.ias.edu/~jn
Solar Neutrinos Before and After KamLAND
We use the recently reported KamLAND measurements on oscillations of reactor
anti-neutrinos, together with the data of previously reported solar neutrino
experiments, to show that: (1) the total 8B neutrino flux emitted by the Sun is
1.00(1.0 \pm 0.06) of the standard solar model (BP00) predicted flux, (2) the
KamLAND measurements reduce the area of the globally allowed oscillation
regions that must be explored in model fitting by six orders of magnitude in
the Delta m^2-tan^2 theta plane, (3) LMA is now the unique oscillation solution
to a CL of 4.7sigma, (4) maximal mixing is disfavored at 3.1 sigma, (5)
active-sterile admixtures are constrained to sin^2 eta<0.13 at 1 sigma, (6) the
observed ^8B flux that is in the form of sterile neutrinos is
0.00^{+0.09}_{-0.00} (1 sigma), of the standard solar model (BP00) predicted
flux, and (7) non-standard solar models that were invented to completely avoid
solar neutrino oscillations are excluded by KamLAND plus solar at 7.9 sigma .
We also refine quantitative predictions for future 7Be and p-p solar neutrino
experiments.Comment: Published version, includes editorial improvement
Lithium Experiment on Solar Neutrinos to Weight the CNO Cycle
The measurement of the flux of beryllium neutrinos with the accuracy of about
10% and CNO neutrinos with the accuracy 30% will enable to find the flux of
pp-neutrinos in the source with the accuracy better than 1% using the
luminosity constraint. The future experiments on \nu e- scattering will enable
to measure with very good accuracy the flux of beryllium and pp-neutrinos on
the Earth. The ratio of the flux of pp-neutrinos on the Earth and in the source
will enable to find with very good accuracy a mixing angle theta solar. Lithium
detector has high sensitivity to CNO neutrinos and can find the contribution of
CNO cycle to the energy generated in the Sun. This will be a stringent test of
the theory of stellar evolution and combined with other experiments will
provide a precise determination of the flux of pp-neutrinos in the source and a
mixing angle theta solar. The work on the development of the technology of
lithium experiment is now in progress.Comment: Minor corrections, one reference added, 11 pages, 2 figures, talk
given at NANP 2003, Dubna, Russia, June 200
Bounds on neutrino magnetic moment tensor from solar neutrinos
Solar neutrinos with non-zero magnetic moments will contribute to the
electron scattering rates in the Super-Kamiokande experiment. The magnetic
moment scattering events in Super-K can be accommodated in the standard VO or
MSW solutions by a change of the parameter space of mass square difference and
mixing angle-but the shifted neutrino parameters obtained from Super-K will
(for some values of neutrino magnetic moments) become incompatible with the
fits from SNO, Gallium and Chlorine experiments. We compute the upper bounds on
the Dirac and Majorana magnetic moments of solar neutrinos by simultaneously
fitting all the observed solar neutrino rates. The bounds the magnetic moment
matrix elements are of the order of 10^{-10} Bohr magnetron.Comment: 9 pages latex file with 6 figures; References added, typos corrected,
matches version to appear in Phys Rev
The value of the fine structure constant over cosmological times
The optical spectra of objects classified as QSOs in the SDSS DR6 are
analyzed with the aim of determining the value of the fine structure constant
in the past and then check for possible changes in the constant over
cosmological timescales. The analysis is done by measuring the position of the
fine structure lines of the [OIII] doublet (4959 and 5008) in QSO nebular
emission. From the sample of QSOs at redshifts z < 0.8 a subsample was selected
on the basis of the amplitude and width of the [OIII] lines. Two different
method were used to determine the position of the lines of the [OIII] doublet,
both giving similar results. Using a clean sample containing 1568 of such
spectra, a value of Delta alpha /alpha=(+2.4 +-2.5) x 10^{-5} (in the range of
redshifts 0-0.8) was determined. The use of a larger number of spectra allows a
factor ~5 improvement on previous constraints based on the same method. On the
whole, we find no evidence of changes in alpha on such cosmological timescales.
The mean variation compatible with our results is 1/ Delta
alpha/alpha=(+0.7 +- 0.7) x 10^{-14} yr^{-1}. The analysis was extended to the
[NeIII] and [SII] doublets, although their usefulness is limited due to the
fact that all these doublets in QSOs tend to be fainter than [OIII], and that
some of them are affected by systematics.Comment: 22 pages, 10 figures. Accepted for publication in Astrophysical
Journa
Constraints on decay plus oscillation solutions of the solar neutrino problem
We examine the constraints on non-radiative decay of neutrinos from the
observations of solar neutrino experiments. The standard oscillation hypothesis
among three neutrinos solves the solar and atmospheric neutrino problems. Decay
of a massive neutrino mixed with the electron neutrino results in the depletion
of the solar neutrino flux. We introduce neutrino decay in the oscillation
hypothesis and demand that decay does not spoil the successful explanation of
solar and atmospheric observations. We obtain a lower bound on the ratio of the
lifetime over the mass of , (\tau_2/m_2) > 22.7 (\srm/\MeV) for the
MSW solution of the solar neutrino problem and (\tau_2/m_2) > 27.8
(\srm/\MeV) for the VO solution (at 99% C.L.).Comment: 8 pages latex file with 4 figure
Vacuum oscillations and excess of high energy solar neutrino events observed in Superkamiokande
The excess of solar-neutrino events above 13 MeV that has been recently
observed by Superkamiokande can be explained by the vacuum oscillation solution
to the Solar Neutrino Problem (SNP). If the boron neutrino flux is 20% smaller
than the standard solar model (SSM) prediction and the chlorine signal is
assumed 30% (or 3.4 sigmas) higher than the measured one, there exists a vacuum
oscillation solution to SNP that reproduces both the observed spectrum of the
recoil electrons, including the high energy distortion, and the other measured
neutrino rates. The most distinct signature of this solution is a semi-annual
seasonal variation of the Be7 neutrino flux with maximal amplitude. While the
temporal series of the GALLEX and Homestake signals suggest that such a
seasonal variation could be present, future detectors (BOREXINO, LENS and
probably GNO) will be able to test it.Comment: ReVTeX, 8 pages, 7 figures included using psfig.sty ; references and
notes adde
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