159 research outputs found

    Optimization of the Two-Baseline Beta-Beam

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    We propose a β\beta-Beam experiment with four source ions and two baselines for the best possible sensitivity to θ13\theta_{13}, CP violation and mass hierarchy. Neutrinos from 18^{18}Ne and 6^6He with Lorentz boost γ=350\gamma=350 are detected in a 500 kton water \chr detector at a distance L=650 km from the source. Neutrinos from 8^8B and 8^8Li are detected in a 50 kton magnetized iron detector at a distance L=7000 km from the source. Since a tilt angle ϑ=34.5\vartheta=34.5^\circ is required to send the beam to the magic baseline, the far end of the ring has a maximum depth of d=2132d=2132 m. We alleviate this problem by proposing to trade reduction of the decay ring with the increase in the boost factor of the 8^8Li and 8^8B ions up to γ8Li=390\gamma_{^8\mathrm{Li}}=390 and γ8Li=650\gamma_{^8\mathrm{Li}}=650, such that the number of events at the detector remains almost the same. We study the sensitivity reach of this two-baseline two-storage ring β\beta-Beam experiment, and compare it with the corresponding reach of the other proposed facilities.Comment: 5 pages. Based on the talk given at Nufact09, Chicago, July 20-25, 2009. Typos correcte

    Combining dark matter detectors and electron-capture sources to hunt for new physics in the neutrino sector

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    In this letter we point out the possibility to study new physics in the neutrino sector using dark matter detectors based on liquid xenon. These are characterized by very good spatial resolution and extremely low thresholds for electron recoil energies. When combined with a radioactive νe\nu_e source, both features in combination allow for a very competitive sensitivity to neutrino magnetic moments and sterile neutrino oscillations. We find that, for realistic values of detector size and source strength, the bound on the neutrino magnetic moment can be improved by an order of magnitude with respect to the present value. Regarding sterile neutrino searches, we find that most of the gallium anomaly could be explored at the 95% confidence level just using shape information.Comment: 5 pages, 2 figures. Minor modifications, references added. Version accepted for publication in JHE

    Reassessing the sensitivity to leptonic CP violation

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    We address the validity of the usual procedure to determine the sensitivity of neutrino oscillation experiments to CP violation. An explicit calibration of the test statistic is performed through Monte Carlo simulations for several experimental setups. We find that significant deviations from a χ2\chi^2 distribution with one degree of freedom occur for experimental setups with low sensitivity to δ\delta. In particular, when the allowed region to which δ\delta is constrained at a given confidence level is comparable to the whole allowed range, the cyclic nature of the variable manifests and the premises of Wilk's theorem are violated. This leads to values of the test statistic significantly lower than a χ2\chi^2 distribution at that confidence level. On the other hand, for facilities which can place better constraints on δ\delta the cyclic nature of the variable is hidden and, as the potential of the facility improves, the values of the test statistics first become slightly higher than and then approach asymptotically a χ2\chi^2 distribution. The role of sign degeneracies is also discussed.Comment: 14 pages, 5 figures, RevTeX4. The discussion of the results has been improved and considerably extended. Version accepted for publication in JHE

    Physics reach of CERN-based SuperBeam neutrino oscillation experiments

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    We compare the physics potential of two representative options for a SuperBeam in Europe, studying the achievable precision at 1\sigma with which the CP violation phase (\delta) could be measured, as well as the mass hierarchy and CP violation discovery potentials. The first setup corresponds to a high energy beam aiming from CERN to a 100 kt liquid argon detector placed at the Pyh\"asalmi mine (2300 km), one of the LAGUNA candidate sites. The second setup corresponds to a much lower energy beam, aiming from CERN to a 500 kt water \v{C}erenkov detector placed at the Gran Sasso underground laboratory (730 km). This second option is also studied for a baseline of 650 km, corresponding to the LAGUNA candidate sites of Umbria and the Canfranc underground laboratory. All results are presented also for scenarios with statistics lowered by factors of 2, 4, 8 and 16 to study the possible reductions of flux, detector mass or running time allowed by the large value of \theta_{13} recently measured.Comment: 15 pages, 4 figure

    Quantifying the sensitivity of oscillation experiments to the neutrino mass ordering

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    Determining the type of the neutrino mass ordering (normal versus inverted) is one of the most important open questions in neutrino physics. In this paper we clarify the statistical interpretation of sensitivity calculations for this measurement. We employ standard frequentist methods of hypothesis testing in order to precisely define terms like the median sensitivity of an experiment. We consider a test statistic TT which in a certain limit will be normal distributed. We show that the median sensitivity in this limit is very close to standard sensitivities based on Δχ2\Delta\chi^2 values from a data set without statistical fluctuations, such as widely used in the literature. Furthermore, we perform an explicit Monte Carlo simulation of the INO, JUNO, LBNE, NOvA, and PINGU experiments in order to verify the validity of the Gaussian limit, and provide a comparison of the expected sensitivities for those experiments.Comment: 41 pages, 13 figures. Version accepted for publication in JHEP. The dependence on the atmospheric mixing angle is now explicitly shown also for long baseline experiments. Minor corrections and references adde