1,877 research outputs found
Large mixing angle solution to the solar neutrino problem and random matter density perturbations
There are reasons to believe that mechanisms exist in the solar interior
which lead to random density perturbations in the resonant region of the Large
Mixing Angle solution to the solar neutrino problem. We find that, in the
presence of these density perturbations, the best fit point in the
(sin^2(2\theta), Delta_m^2) parameter space moves to smaller values, compared
with the values obtained for the standard LMA solution. Combining solar data
with KamLAND results, we find a new compatibility region, which we call
VERY-LOW LMA, where sin^2(2\theta) ~ 0.6 and Delta_m^2~2e-5 eV^2, for random
density fluctuations of order 5% < \xi< 8%. We argue that such values of
density fluctuations are still allowed by helioseismological observations at
small scales of order 10 - 1000 km deep inside the solar core.Comment: References and discussion added, with some small numerical
corrections implemente
The Clustering Characteristics of HI-Selected Galaxies from the 40% ALFALFA Survey
The 40% Arecibo Legacy Fast ALFA (ALFALFA) survey catalog (\alpha.40) of
approximately 10,150 HI-selected galaxies is used to analyze the clustering
properties of gas-rich galaxies. By employing the Landy-Szalay estimator and a
full covariance analysis for the two-point galaxy-galaxy correlation function,
we obtain the real-space correlation function and model it as a power law,
\xi(r) = (r/r_0)^(-\gamma), on scales less than 10 h^{-1} Mpc. As the largest
sample of blindly HI-selected galaxies to date, \alpha.40 provides detailed
understanding of the clustering of this population. We find \gamma = 1.51 +/-
0.09 and r_0 = 3.3 +0.3, -0.2 h^{-1} Mpc, reinforcing the understanding that
gas-rich galaxies represent the most weakly clustered galaxy population known;
we also observe a departure from a pure power law shape at intermediate scales,
as predicted in \Lambda CDM halo occupation distribution models. Furthermore,
we measure the bias parameter for the \alpha.40 galaxy sample and find that HI
galaxies are severely antibiased on small scales, but only weakly antibiased on
large scales. The robust measurement of the correlation function for gas-rich
galaxies obtained via the \alpha.40 sample constrains models of the
distribution of HI in simulated galaxies, and will be employed to better
understand the role of gas in environmentally-dependent galaxy evolution.Comment: 30 pages, 10 figures, accepted by Ap
Easylife: the data reduction and survey handling system for VIPERS
We present Easylife, the software environment developed within the framework
of the VIPERS project for automatic data reduction and survey handling.
Easylife is a comprehensive system to automatically reduce spectroscopic data,
to monitor the survey advancement at all stages, to distribute data within the
collaboration and to release data to the whole community. It is based on the
OPTICON founded project FASE, and inherits the FASE capabilities of modularity
and scalability. After describing the software architecture, the main reduction
and quality control features and the main services made available, we show its
performance in terms of reliability of results. We also show how it can be
ported to other projects having different characteristics.Comment: pre-print, 17 pages, 4 figures, accepted for publication in
Publications of the Astronomical Society of the Pacifi
Effects of magnetohydrodynamics matter density fluctuations on the solar neutrino resonant spin-flavor precession
Taking into account the stringent limits from helioseismology observations on
possible matter density fluctuations described by magnetohydrodynamics theory,
we find the corresponding time variations of solar neutrino survival
probability due to the resonant spin-flavor precession phenomenon with
amplitude of order O(10%). We discuss the physics potential of high statistics
real time experiments, like as Superkamiokande, to observe the effects of such
magnetohydrodynamics fluctuations on their data. We conclude that these
observations could be thought as a test of the resonant spin-flavor precession
solution to the solar neutrino anomaly.Comment: 16 pages, 3 figure
Neutrino Decay and Solar Neutrino Seasonal Effect
We consider the possibility of solar neutrino decay as a sub-leading effect
on their propagation between production and detection. Using current
oscillation data, we set a new lower bound to the neutrino lifetime at
at
C.L.. Also, we show how seasonal variations in the solar neutrino data
can give interesting additional information about neutrino lifetime
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