Effects of non-standard neutrino interactions on MSW-LMA solution to the solar neutrino problem

We show that the non-standard neutrino interactions can play a role as sub-leading effect on the solar neutrino oscillations. We observe that very small flavor universality violations of order of 0.1-0.2 G_F is sufficient to induce two phenomena: suppression of the eletronic neutrino earth regeneration and a shift of the resonance layer in the sun. We obtain these phenomena even in the absence of any flavor changing interactions. We discuss their consequences and confront with a global analysis of solar+KamLAND results. We conclude that a new compatibility region in the Delta m^2 x tan^2\theta, which we call very low Large Mixing Angle region, is found for Delta m^2 ~ 1e-5 eV^2 and tan^2\theta= 0.45.Comment: references added, small changes in text, some changes in predictions of KamLAND future sensitivity to NSNI parameter

Short-Baseline Neutrino Oscillations at a Neutrino Factory

Within the framework of three-neutrino and four-neutrino scenarios that can describe the results of the LSND experiment, we consider the capabilities of short baseline neutrino oscillation experiments at a neutrino factory. We find that, when short baseline (L \alt 100 km) neutrino factory measurements are used together with other accelerator-based oscillation results, the complete three-neutrino parameter space can best be determined by measuring the rate of $\nu_e \to \nu_\tau$ oscillations, and measuring CP violation with either $\nu_e \to \nu_\mu$ or $\nu_\mu \to \nu_\tau$ oscillations (including the corresponding antineutrino channels). With measurements of CP violation in both $\nu_e \to \nu_\mu$ and $\nu_\mu \to \nu_\tau$ it may be possible to distinguish between the three- and four-neutrino cases.Comment: 16 pages, Revtex (single-spaced), 8 postscript figures, uses epsf.st

Status of a hybrid three-neutrino interpretation of neutrino data

We reanalyze the non-standard interaction (NSI) solutions to the solar neutrino problem in the light of the latest solar, atmospheric and reactor neutrino data. We show that such solutions, although preferred by the solar data and consistent with the oscillation description of the atmospheric neutrino data, are ruled out by the first results of the KamLAND reactor experiment, at more than 3_sigma.Comment: 19 pages, LaTeX file using Elsart, 2 tables and 4 figures included. This version updates the one published in Nucl.Phys.B629:479-490,2002 by including the new KamLAND dat

Second-order corrections to neutrino two-flavor oscillation parameters in the wave packet approach

We report about an analytic study involving the {\em intermediate} wave packet formalism for quantifying the physically relevant information which appear in the neutrino two-flavor conversion formula and help us to obtain more precise limits and ranges for neutrino flavor oscillation. By following the sequence of analytic approximations where we assume a strictly peaked momentum distribution and consider the second-order corrections in a power series expansion of the energy, we point out a {\em residual} time-dependent phase which, coupled with the {\em spreading/slippage} effects, can subtly modify the neutrino oscillation parameters and limits. Such second-order effects are usually ignored in the relativistic wave packet treatment, but they present an evident dependence on the propagation regime so that some small modifications to the oscillation pattern, even in the ultra-relativistic limit, can be quantified. These modifications are implemented in the confront with the neutrino oscillation parameter range (mass-squared difference \Delta m^{\2} and the mixing-angle $\theta$) where we assume the same wave packet parameters previously noticed in the literature in a kind of {\em toy model} for some reactor experiments. Generically speaking, our analysis parallels the recent experimental purposes which concern with higher precision parameter measurements. To summarize, we show that the effectiveness of a more accurate determination of \Delta m^{\2} and $\theta$ depends on the wave packet width $a$ and on the averaged propagating energy flux $\bar{E}$ which still correspond to open variables for some classes of experiments. \Comment: 25 pages, 5 figure

Status of a Supersymmetric Flavour Violating Solution to the Solar Neutrino Puzzle with Three Generations

We present a general study of a three neutrino flavour transition model based on the supersymmetric interactions which violate R-parity. These interactions induce flavour violating scattering reactions between solar matter and neutrinos. The model does not contain any vacuum mass or mixing angle for the first generation neutrino. Instead, the effective mixing in the first generation is induced via the new interactions. The model provides a natural interpretation of the atmospheric neutrino anomaly, and is consistent with reactor experiments. We determine all R-parity violating couplings which can contribute to the effective neutrino oscillations, and summarize the present laboratory bounds. Independent of the specific nature of the (supersymmetric) flavour violating model, the experimental data on the solar neutrino rates and the recoil electron energy spectrum are inconsistent with the theoretical predictions. The confidence level of the $\chi^2$-analysis ranges between $\sim 10^{-4}$ and $\sim 10^{-3}$. The incompatibility, is due to the new SNO results, and excludes the present model. We conclude that a non-vanishing vacuum mixing angle for the first generation neutrino is necessary in our model. We expect this also to apply to the solutions based on other flavour violating interactions having constraints of the same order of magnitude.Comment: 17 pages, Latex fil

Light Lambda-Lambda Hypernuclei and the Onset of Stability for Lambda-Xi Hypernuclei

New Faddeev-Yakubovsky calculations for light Lambda-Lambda hypernuclei are presented in order to assess the self consistency of the Lambda-Lambda hypernuclear binding-energy world data and the implied strength of the Lambda-Lambda interaction, in the wake of recent experimental reports on Lambda-Lambda-4H and Lambda-Lambda-6He. Using Gaussian soft-core simulations of Nijmegen one-boson-exchange model interactions, the Nijmegen soft-core model NSC97 simulations are found close to reproducing the recently reported binding energy of Lambda-Lambda-6He, but not those of other species. For stranger systems, Faddeev calculations of light Lambda-Xi hypernuclei, using a simulation of the strongly attractive Lambda-Xi interactions due to the same model, suggest that Lambda-Xi-6He marks the onset of nuclear stability for Xi hyperons.Comment: 5 pages, 3 postscript figures; fig.2 replaced, minor changes, accepted as Rapid Communication in PR

Atmospheric Neutrino Oscillations and New Physics

We study the robustness of the determination of the neutrino masses and mixing from the analysis of atmospheric and K2K data under the presence of different forms of phenomenologically allowed new physics in the nu_mu--nu_tau sector. We focus on vector and tensor-like new physics interactions which allow us to treat, in a model independent way, effects due to the violation of the equivalence principle, violations of the Lorentz invariance both CPT conserving and CPT violating, non-universal couplings to a torsion field and non-standard neutrino interactions with matter. We perform a global analysis of the full atmospheric data from SKI together with long baseline K2K data in the presence of nu_mu -> nu_tau transitions driven by neutrino masses and mixing together with sub-dominant effects due to these forms of new physics. We show that within the present degree of experimental precision, the extracted values of masses and mixing are robust under those effects and we derive the upper bounds on the possible strength of these new interactions in the nu_mu--nu_tau sector.Comment: 22 pages, LaTeX file using RevTEX4, 5 figures and 4 tables include

Current Status of the Resonant Spin-Flavor Precession Solution to the Solar Neutrino Problem

We discuss the current status of the resonant spin-flavor precession (RSFP) solution to the solar neutrino problem. We perform a fit to all the latest solar neutrino data for various assumed magnetic field profiles in the sun. We show that the RSFP can account for all the solar neutrino experiments, giving as good fit as other alternative solutions such as MSW or Just so, and therefore can be a viable solution to the solar neutrino problemComment: RevTex file, 9 pages, 12 postscript figures, Some errors are corrected, some changes in results but no change in conclusions, version to appear in Astroparticle Physic

Can lepton flavor violating interactions explain the LSND results?

If the atmospheric and the solar neutrino problem are both explained by neutrino oscillations, and if there are only three light neutrinos, then all mass-squared differences between the neutrinos are known. In such a case, existing terrestrial neutrino oscillation experiments cannot be significantly affected by neutrino oscillations, but, in principle there could be an anomaly in the neutrino flux due to new neutrino interactions. We discuss how a non-standard muon decay $\mu^+ \to e^+ \bar\nu_e \nu_\ell$ would modify the neutrino production processes of these experiments. Since $SU(2)_L$ violation is small for New Physics above the weak scale one can use related flavor-violating charged lepton processes to constrain these decays in a model independent way. We show that the upper bounds on $\mu \to 3e$, muonium-antimuonium conversion and $\tau \to \mu e e$ rule out any observable effect for the present experiments due to $\mu^+ \to e^+ \bar\nu_e \nu_\ell$ for $\ell=e,\mu,\tau$, respectively. Applying similar arguments to flavor-changing semi-leptonic reactions we exclude the possibility that the "oscillation signals" observed at LSND are due to flavor-changing interactions that conserve total lepton number.Comment: 21 pages, 6 figures, Latex; minor correction