151 research outputs found

    Probing the deviation from maximal mixing of atmospheric neutrinos

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    Pioneering atmospheric muon neutrino experiments have demonstrated the near-maximal magnitude of the flavor mixing angle θ23\theta_{23}. But the precise value of the deviation D1/2sin2θ23D \equiv 1/2 - \sin^2 \theta_{23} from maximality (if nonzero) needs to be known, being of great interest -- especially to builders of neutrino mass and mixing models. We quantitatively investigate in a three generation framework the feasibility of determining DD in a statistically significant manner from studies of the atmospheric νμ,νˉμ\nu_\mu,\bar\nu_\mu survival probability including both vacuum oscillations and matter effects. We show how this determination will be sharpened by considering the up-down ratios of observed νμ\nu_\mu- and νˉμ\bar\nu_\mu-induced events and the differences of these ratios in specified energy and zenith angle bins. We consider 1 Megaton year of exposure to a magnetized iron calorimeter such as the proposed INO detector ICAL, taking into account both energy and zenith angle resolution functions. The sensitivity of such an exposure and the dependence of the determination of DD on the concerned oscillation parameters are discussed in detail. The vital use of matter effects in fixing the octant of θ23\theta_{23} is highlighted.Comment: Version to appear in PR

    Viewing Lepton Mixing through the Cabibbo Haze

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    We explore the hypothesis that the Cabibbo angle is an expansion parameter for lepton as well as quark mixing. Cabibbo effects are deviations from zero mixing for the quarks but are deviations from unknown mixings for the leptons, such that lepton mixing is veiled by a Cabibbo haze. We present a systematic classification of parametrizations and catalog the leading order Cabibbo effects. We find that the size of the CHOOZ angle is not always correlated with the observability of CP violation. This phenomenological approach has practical merit both as a method for organizing top-down flavor models and as a guideline for planning future experiments.Comment: References added, minor typos fixe

    Direct determination of the solar neutrino fluxes from solar neutrino data

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    We determine the solar neutrino fluxes from a global analysis of the solar and terrestrial neutrino data in the framework of three-neutrino mixing. Using a Bayesian approach we reconstruct the posterior probability distribution function for the eight normalization parameters of the solar neutrino fluxes plus the relevant masses and mixing, with and without imposing the luminosity constraint. This is done by means of a Markov Chain Monte Carlo employing the Metropolis-Hastings algorithm. We also describe how these results can be applied to test the predictions of the Standard Solar Models. Our results show that, at present, both models with low and high metallicity can describe the data with good statistical agreement.Comment: 24 pages, 1 table, 7 figures. Acknowledgments correcte

    Neutrino Coherent Scattering Rates at Direct Dark Matter Detectors

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    Neutrino-induced recoil events may constitute a background to direct dark matter searches, particularly for those detectors that strive to reach the ton-scale and beyond. This paper discusses the expected neutrino-induced background spectrum due to several of the most important sources, including solar, atmospheric, and diffuse supernova neutrinos. The largest rate arises from 8^8B produced solar neutrinos, providing upwards of 103\sim 10^3 events per ton-year over all recoil energies for the heaviest nuclear targets. However the majority of these 8^8B events are expected to be below the recoil threshold of modern detectors. The remaining neutrino sources are found to constitute a background to the WIMP-induced recoil rate only if the WIMP-nucleon cross section is less than 101210^{-12} pb. Finally the sensitivity to diffuse supernova neutrino flux for non-electron neutrino flavors is discussed, and projected flux limits are compared with existing flux limits

    Astroparticle physics with solar neutrinos

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    Solar neutrino experiments observed fluxes smaller than the expectations from the standard solar model. This discrepancy is known as the “solar neutrino problem”. Flux measurements by Super-Kamiokande and SNO have demonstrated that the solar neutrino problem is due to neutrino oscillations. Combining the results of all solar neutrino experiments, parameters for solar neutrino oscillations are obtained. Correcting for the effect of neutrino oscillations, the observed neutrino fluxes are consistent with the prediction from the standard solar model. In this article, results of solar neutrino experiments are reviewed with detailed descriptions of what Kamiokande and Super-Kamiokande have contributed to the history of astroparticle physics with solar neutrino measurements

    A first search of excited states double beta and double electron capture decays of Pd110 and Pd102

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    A search for double beta decays of the palladium isotopes 110Pd and 102Pd into excited states of their daughters was performed and first half-life limits for the 2{\nu}{\beta}{\beta} and 0{\nu}{\beta}{\beta} decays into first excited 0+ and 2+ states of 5.89e19 yr and 4.40e19 yr (95% CL) for the 110Pd decay were obtained. The half-life limits for the corresponding double electron capture transition of 102Pd are 7.64e18 yr and 2.68e18 yr (95% CL) respectively. These are the first measurements for 102Pd.Comment: Updated to published version. Refined analysis and minor text changes. Half-life limits change

    Two Gallium data sets, spin flavour precession and KamLAND

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    We reexamine the possibility of a time modulation of the low energy solar neutrino flux which is suggested by the average decrease of the Ga data in line with our previous arguments. We perform two separate fits to the solar neutrino data, one corresponding to 'high' and the other to 'low' Ga data, associated with low and high solar activity respectively. We therefore consider an alternative to the conventional solar+KamLAND fitting, which allows one to explore the much wider range of the θ12\theta_{12} angle permitted by the KamLAND fitting alone. We find a solution with parameters Δm212=8.2×105eV2,tan2θ=0.31\Delta m^2_{21}=8.2\times 10^{-5} eV^2, tan^{2}\theta=0.31 in which the 'high' and the 'low' Ga rates lie far apart and are close to their central values and is of comparable quality to the global best fit, where these rates lie much closer to each other. This is an indication that the best fit in which all solar and KamLAND data are used is not a good measure of the separation of the two Ga data sets, as the information from the low energy neutrino modulation is dissimulated in the wealth of data. Furthermore for the parameter set proposed one obtains an equally good fit to the KamLAND energy spectrum and an even better fit than the 'conventional' LMA one for the reactor antineutrino survival probability as measured by KamLAND.Comment: V2: 15 pages, 3 eps figures, fit improved, final version to appear in Journal of Physics

    High sensitivity measurement of 224Ra and 226Ra in water with an improved hydrous titanium oxide technique at the Sudbury Neutrino Observatory

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    The existing hydrous titanium oxide (HTiO) technique for the measurement of 224Ra and 226Ra in the water at the Sudbury Neutrino Observatory (SNO) has been changed to make it faster and less sensitive to trace impurities in the HTiO eluate. Using HTiO-loaded filters followed by cation exchange adsorption and HTiO co-precipitation, Ra isotopes from 200-450 tonnes of heavy water can be extracted and concentrated into a single sample of a few millilitres with a total chemical efficiency of 50%. Combined with beta-alpha coincidence counting, this method is capable of measuring 2.0x10^3 uBq/kg of 224Ra and 3.7x10^3 uBq/kg of 226Ra from the 232Th and 238U decay chains, respectively, for a 275 tonne D2O assay, which are equivalent to 5x10^16 g Th/g and 3x10^16 g U/g in heavy water.Comment: 8 Pages, 2 figures and 2 table
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