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 $\nu_2$ neutrino lifetime at $\tau_2\, /\, m_2 \geq 7.2 \times 10^{-4}\,\,\hbox{s}\,.\,\hbox{eV}^{-1}$ at $99\%\,$C.L.. Also, we show how seasonal variations in the solar neutrino data can give interesting additional information about neutrino lifetime