Improving LMA predictions with non standard interactions

It has been known for some time that the well established LMA solution to the observed solar neutrino deficit fails to predict a flat energy spectrum for SuperKamiokande as opposed to what the data indicates. It also leads to a Chlorine rate which appears to be too high as compared to the data. We investigate the possible solution to these inconsistencies with non standard neutrino interactions, assuming that they come as extra contributions to the $\nu_{\alpha}\nu_{\beta}$ and $\nu_{\alpha}e$ vertices that affect both the propagation of neutrinos through solar matter and their detection. We find that, among the many possibilities for non standard couplings, only one of them leads to a flat SuperKamiokande spectral rate in better agreement with the data and predicts a Chlorine rate within 1$\sigma$ of the observed one, while keeping all other predictions accurate

Improving LMA predictions with non-standard interactions: neutrino decay in solar matter?

It has been known for some time that the well established LMA solution to the observed solar neutrino deficit fails to predict a flat energy spectrum for SuperKamiokande as opposed to what the data indicates. It also leads to a Chlorine rate which appears to be too high as compared to the data. We investigate the possible solution to these inconsistencies with non standard neutrino interactions, assuming that they come as extra contributions to the $\nu_{\alpha}\nu_{\beta}$ and $\nu_{\alpha}e$ vertices that affect both the propagation of neutrinos in the sun and their detection. We find that, among the many possibilities for non standard couplings, only the diagonal imaginary ones lead to a solution to the tension between the LMA predictions and the data, implying neutrino instability in the solar matter. Unitarity requirements further restrict the solution and a neutrino decay into an antineutrino and a majoron within the sun is the one favoured. Antineutrino probability is however too small to open the possibility of experimentally observing antineutrinos from the sun due to NSI.Comment: 27 pages, 8 figures. Final version to be published in Physical Review

Neutrino Mass Matrices with Vanishing Determinant and θ13\theta_{13}

We investigate the prospects for scenarios with vanishing determinant neutrino mass matrices and vanishing $\theta_{13}$ mixing angle. Normal and inverse mass hierarchies are considered separately. For normal hierarchy it is found that neutrinoless double beta decay cannot be observed by any of the present or next generation experiments. For inverse hierarchy the neutrinoless double beta decay is, on the contrary, accessible to experiments. We also analyse for both hierarchies the case for texture zeros and equalities between mass matrix elements. No texture zeros are found to be possible nor any such equalities, apart from the obvious ones.Comment: 14 pages, 1 figur

Precovery of near-Earth asteroids by a citizen-science project of the Spanish Virtual Observatory

This article describes a citizen-science project conducted by the Spanish Virtual Observatory (SVO) to improve the orbits of near-Earth asteroids (NEAs) using data from astronomical archives. The list of NEAs maintained at the Minor Planet Center (MPC) is checked daily to identify new objects or changes in the orbital parameters of already catalogued objects. Using NEODyS we compute the position and magnitude of these objects at the observing epochs of the 938 046 images comprising the Eigth Data Release of the Sloan Digitised Sky Survey (SDSS). If the object lies within the image boundaries and the magnitude is brighter than the limiting magnitude, then the associated image is visually inspected by the project's collaborators (the citizens) to confirm or discard the presence of the NEA. If confirmed, accurate coordinates and, sometimes, magnitudes are submitted to the MPC. Using this methodology, 3,226 registered users have made during the first fifteen months of the project more than 167,000 measurements which have improved the orbital elements of 551 NEAs (6% of the total number of this type of asteroids). Even more remarkable is the fact that these results have been obtained at zero cost to telescope time as NEAs were serendipitously observed while the survey was being carried out. This demonstrates the enormous scientific potential hidden in astronomical archives. The great reception of the project as well as the results obtained makes it a valuable and reliable tool for improving the orbital parameters of near-Earth asteroids.Comment: 9 pages, 5 figures. Accepted in Astron. Nach

KamLAND and Solar Antineutrino Spectrum

We use the recent KamLAND observations to predict the solar antineutrino spectrum at some confidence limits. We find that a scaling of the antineutrino probability with respect to the magnetic field profile --in the sense that the same probability function can be reproduced by any profile with a suitable peak field value-- can be utilised to obtain a general shape of the solar antineutrino spectrum. This scaling and the upper bound on the solar antineutrino event rate, that can be derived from the data, lead to: 1) an upper bound on the solar antineutrino flux, 2) the prediction of their energy spectrum, as the normalisation of the spectrum can be obtained from the total number of antineutrino events recorded in the experiment. We get $\phi_{\bar\nu}<3.8\times 10^{-3}\phi(^8B)$ or $\phi_{\bar\nu} <5.5\times 10^{-3}\phi(^8B)$ at 95% CL, assuming Gaussian or Poissonian statistics, respectively. And for 90% CL these become $\phi_{\bar\nu}<3.4 \times 10^{-3}\phi(^8B)$ and $\phi_{\bar\nu}<4.9\times 10^{-3}\phi(^8B)$. It shows an improvement by a factor of 3-5 with respect to existing bounds. These limits are quite general and independent of the detailed structure of the magnetic field in the solar interior.Comment: Based on talk given at NANP'03, JINR Dubna, Russia, June 2003. To be published in "Physics of Atomic Nuclie

Solar Neutrinos: Spin Flavour Precession and LMA

The time dependence that appears to be hinted by the data from the first 13 years of the solar neutrino Gallium experiments is viewed as resulting from a partial conversion of active neutrinos to light sterile ones through the resonant interaction between the magnetic moment of the neutrino and a varying solar field. A summary of the model and its predictions are presented for the forthcoming experiments Borexino and LENS.Comment: 6 pages, 3 figures, contribution to 12th Lomonosov Conference in Elementary Particle Physics, Moscow, Aug 24-31 (2005