251 research outputs found

    Tau contamination in the platinum channel at neutrino factories

    Full text link
    The platinum channel (\nu_e or anti-\nu_e appearance) has been proposed at neutrino factories as an additional channel that could help in lifting degeneracies and improving sensitivities to neutrino oscillation parameters, viz., \theta_{13}, \delta_{CP}, mass hierarchy, deviation of \theta_{23} from maximality and its octant. This channel corresponds to \nu_\mu -> \nu_e (or the corresponding anti-particle) oscillations of the initial neutrino flux, with the subsequent detection of (positrons) electrons from charged current interactions of the (anti-) \nu_e in the detector. For small values of \theta_{13}, the dominant \nu_\mu \to \nu_\tau (or corresponding anti-particle) oscillation results in this signal being swamped by electrons arising from the leptonic decay of taus produced in charge-current interactions of \nu_\tau (anti-\nu_\tau) with the detector. We examine for the first time the role of this tau contamination to the electron events sample and find that it plays a significant role in the platinum channel compared to other channels, not only at high energy neutrino factories but surprisingly even at low energy neutrino factories. Even when the platinum channel is considered in combination with other channels such as the golden (muon appearance) or muon disappearance channel, the tau contamination results in a loss in precision of the measured parameters.Comment: 13 pages latex file with 10 eps figure file

    Minimal extension of tri-bimaximal mixing and generalized Z_2 X Z_2 symmetries

    Full text link
    We discuss consequences of combining the effective Z2×Z2Z_2\times Z_2 symmetry of the tri-bimaximal neutrino mass matrix with the CP symmetry. Imposition of such generalized Z2×Z2Z_2\times Z_2 symmetries leads to predictive neutrino mass matrices determined in terms of only four parameters and leads to non-zero θ13\theta_{13} and maximal atmospheric mixing angle and CP violating phase. It is shown that an effective generalized Z2×Z2Z_2\times Z_2 symmetry of the mass matrix can arise from the A4A_4 symmetry with specific vacuum alignment. The neutrino mass matrix in the considered model has only three real parameters and leads to determination of the absolute neutrino mass scale as a function of the reactor angle θ13\theta_{13}.Comment: References added, accepted for publication in Phys. Rev. D (Rapid Communication

    Simple renormalizable flavor symmetry for neutrino oscillations

    Full text link
    The recent measurement of a non-zero neutrino mixing angle θ13\theta_{13} requires a modification of the tri-bimaximal mixing pattern that predicts a zero value for it. We propose a new neutrino mixing pattern based on a spontaneously-broken A4A_{4} flavor symmetry and a type-I seesaw mechanism. Our model allows for approximate tri-bimaximal mixing and non-zero θ13\theta_{13}, and contains a natural way to implement low and high energy CP violation in neutrino oscillations, and leptogenesis with a renormalizable Lagrangian. Both normal and inverted mass hierarchies are permitted within 3σ3\sigma experimental bounds, with the prediction of small (large) deviations from maximality in the atmospheric mixing angle for the normal (inverted) case. Interestingly, we show that the inverted case is excluded by the global analysis in 1σ1\sigma experimental bounds, while the most recent MINOS data seem to favor the inverted case. Our model make predictions for the Dirac CP phase in the normal and inverted hierarchies, which can be tested in near-future neutrino oscillation experiments. Our model also predicts the effective mass mee|m_{ee}| measurable in neutrinoless double beta decay to be in the range 0.04mee0.150.04\lesssim |m_{ee}| \lesssim 0.15 eV for the normal hierarchy and 0.06mee0.110.06\lesssim |m_{ee}| \lesssim 0.11 eV for the inverted hierarchy, both of which are within the sensitivity of the next generation experiments.Comment: 29 pages and 10 figures. No corrections. Version for Phys. Rev.

    Systematic errors and backgrounds for a Double-CHOOZ experiments

    Get PDF

    SEARCH FOR NEUTRINO OSCILLATION AT BUGEY

    Get PDF
    The high flux of low energy [MATH]e produced by the core of a PWR reactor of Bugey power plant has been used to search for evidence of neutrino oscillations through the inverse beta decay reaction [MATH]e + p → e+ + n. Measurements have been performed at two distances (13.5 and 18.5m). About 50 000 [MATH]e events have been collected at the first position and 25 000 [MATH]e events at the second one. Data analysis is almost completed

    Nonzero theta_13 signals nonmaximal atmospheric neutrino mixing

    Full text link
    From recent groundbreaking experiments, it is now known that the Pontecorvo-Maki-Nakagawa-Sakata mixing differs significantly from the tribimaximal model in which theta_13=0 and theta_23=pi/4. Flavor symmetry can require that the departures from these two equations are linearly related. T' and A_4, which successfully accommodated the pre-T2K Pontecorvo-Maki-Nakagawa-Sakata matrix, predict that 38.07 deg.< theta_23 <39.52 deg. at 95% C.L.. The best fit values, combining the model predictions with T2K, MINOS, Double Chooz, Daya Bay, and RENO data, are theta_23=38.7 deg. and theta_13=8.9 deg..Comment: 4 pages, 1 figure. Published version Phys. Rev.

    The Waveform Digitiser of the Double Chooz Experiment: Performance and Quantisation Effects on PhotoMultiplier Tube Signals

    Full text link
    We present the waveform digitiser used in the Double Chooz experiment. We describe the hardware and the custom-built firmware specifically developed for the experiment. The performance of the device is tested with regards to digitising low light level signals from photomultiplier tubes and measuring pulse charge. This highlights the role of quantisation effects and leads to some general recommendations on the design and use of waveform digitisers.Comment: 14 pages, 8 figures, accepted for publication in JINS

    Lorentz- and CPT-violating models for neutrino oscillations

    Get PDF
    A class of calculable global models for neutrino oscillations based on Lorentz and CPT violation is presented. One simple example matches established neutrino data from accelerator, atmospheric, reactor, and solar experiments, using only two degrees of freedom instead of the usual five. A third degree of freedom appears in the model, and it naturally generates the MiniBooNE low-energy anomalies. More involved models in this class can also accommodate the LSND anomaly and neutrino-antineutrino differences of the MINOS type. The models predict some striking signals in various ongoing and future experiments.Comment: 17 pages two-column REVTe

    Initial Results from the CHOOZ Long Baseline Reactor Neutrino Oscillation Experiment

    Get PDF
    Initial results are presented from CHOOZ, a long-baseline reactor-neutrino vacuum-oscillation experiment. Electron antineutrinos were detected by a liquid scintillation calorimeter located at a distance of about 1 km. The detector was constructed in a tunnel protected from cosmic rays by a 300 MWE rock overburden. This massive shielding strongly reduced potentially troublesome backgrounds due to cosmic-ray muons, leading to a background rate of about one event per day, more than an order of magnitude smaller than the observed neutrino signal. From the statistical agreement between detected and expected neutrino event rates, we find (at 90% confidence level) no evidence for neutrino oscillations in the electron antineutrino disappearance mode for the parameter region given approximately by deltam**2 > 0.9 10**(-3) eV**2 for maximum mixing and (sin(2 theta)**2) > 0.18 for large deltam**2.Comment: 13 pages, Latex, submitted to Physics Letters

    Search for neutrino oscillations on a long base-line at the CHOOZ nuclear power station

    Get PDF
    This final article about the CHOOZ experiment presents a complete description of the electron antineutrino source and detector, the calibration methods and stability checks, the event reconstruction procedures and the Monte Carlo simulation. The data analysis, systematic effects and the methods used to reach our conclusions are fully discussed. Some new remarks are presented on the deduction of the confidence limits and on the correct treatment of systematic errors.Comment: 41 pages, 59 figures, Latex file, accepted for publication by Eur.Phys.J.
    corecore