6 research outputs found
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Precision muon reconstruction in Double Chooz
We describe a muon track reconstruction algorithm for the reactor anti-neutrino experiment Double Chooz. The Double Chooz detector consists of two optically isolated volumes of the liquid scintillator viewed by PMTs, and an Outer Veto above these made of crossed scintillator strips. Muons are reconstructed by their Outer Veto hit positions along with timing information from the other two detector volumes. All muons are fit under the hypothesis that they are through-going and ultrarelativistic. If the energy depositions suggest that the muon may have stopped, the reconstruction fits also for this hypothesis and chooses between the two via the relative goodness-of-fit. In the ideal case of a through-going muon intersecting the center of the detector, the resolution is ~40mm in each transverse dimension. High quality muon reconstruction is an important tool for reducing the impact of the cosmogenic isotope background in Double Chooz. © 2014 Elsevier B.V
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First measurement of ?13 from delayed neutron capture on hydrogen in the Double Chooz experiment
The Double Chooz experiment has determined the value of the neutrino oscillation parameter ?13 from an analysis of inverse beta decay interactions with neutron capture on hydrogen. This analysis uses a three times larger fiducial volume than the standard Double Chooz assessment, which is restricted to a region doped with gadolinium (Gd), yielding an exposure of 113.1 GW-ton-years. The data sample used in this analysis is distinct from that of the Gd analysis, and the systematic uncertainties are also largely independent, with some exceptions, such as the reactor neutrino flux prediction. A combined rate- and energy-dependent fit finds sin22?13=0.097±0.034 (stat.)±0.034 (syst.), excluding the no-oscillation hypothesis at 2.0. This result is consistent with previous measurements of sin22?13
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Background-independent measurement of ?13 in Double Chooz
The oscillation results published by the Double Chooz Collaboration in 2011 and 2012 rely on background models substantiated by reactor-on data. In this analysis, we present a background-model-independent measurement of the mixing angle ?13 by including 7.53 days of reactor-off data. A global fit of the observed antineutrino rates for different reactor power conditions is performed, yielding a measurement of both ?13 and the total background rate. The results on the mixing angle are improved significantly by including the reactor-off data in the fit, as it provides a direct measurement of the total background rate. This reactor rate modulation analysis considers antineutrino candidates with neutron captures on both Gd and H, whose combination yields sin2(2?13) = 0.102 ± 0.028(stat.) ± 0.033(syst.). The results presented in this study are fully consistent with the ones already published by Double Chooz, achieving a competitive precision. They provide, for the first time, a determination of ?13 that does not depend on a background model
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Reactor ? ÂŻe disappearance in the Double Chooz experiment
The Double Chooz experiment has observed 8249 candidate electron antineutrino events in 227.93 live days with 33.71GW-ton-years (reactor power×detector mass×live time) exposure using a 10.3m3 fiducial volume detector located at 1050m from the reactor cores of the Chooz nuclear power plant in France. The expectation in case of ? 13=0 is 8937 events. The deficit is interpreted as evidence of electron antineutrino disappearance. From a rate plus spectral shape analysis we find sin22? 13=0.109±0.030(stat)±0.025(syst) . The data exclude the no-oscillation hypothesis at 99.8%CL (2.9s)
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Improved measurements of the neutrino mixing angle O13 with the double chooz detector
The Double Chooz experiment presents improved measurements of the neutrino mixing angle O13 using the data collected in 467.90 live days from a detector positioned at an average distance of 1050m from two reactor cores at the Chooz nuclear power plant. Several novel techniques have been developed to achieve significant reductions of the backgrounds and systematic uncertainties with respect to previous publications, whereas the efficiency of the (Formula Presented.) signal has increased. The value of O13 is measured to be sin22O13 = 0.090-0.029+0.032 from a fit to the observed energy spectrum. Deviations from the reactor (Formula Presented.) prediction observed above a prompt signal energy of 4MeV and possible explanations are also reported. A consistent value of O13 is obtained from a fit to the observed rate as a function of the reactor power independently of the spectrum shape and background estimation, demonstrating the robustness of the O13 measurement despite the observed distortion
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Final NOMAD results on muon-neutrino ---> tau-neutrino and electron-neutrino ---> tau-neutrino oscillations including a new search for tau-neutrino appearance using hadronic tau decays.
Results from the ?t appearance search in a neutrino beam using the full NOMAD data sample are reported. A new analysis unifies all the hadronic t decays, significantly improving the overall sensitivity of the experiment to oscillations. The “blind analysis” of all topologies yields no evidence for an oscillation signal. In the two-family oscillation scenario, this sets a 90% CL allowed region in the sin22?µt–?m2 plane which includes sin22?µt<3.3×10-4 at large ?m2 and ?m2< 0.7 eV2/c4 at sin22?µt=1. The corresponding contour in the ?e??t oscillation hypothesis results in sin22?et<1.5×10-2 at large ?m2 and ?m2<5.9 eV2/c4 at sin22?et=1. We also derive limits on effective couplings of the t lepton to ?µ or ?e