Browsing by Author "Busenitz, J."
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Item Background-independent measurement of theta(13) in Double Chooz(Elsevier, 2014) Double Chooz Collaboration; Busenitz, J.; Elnimr, M.; Fernandes, S.M.; Konno, T.; Kuze, M.; Sharankova, R.; Stancu, I.; RWTH Aachen University; University of Alabama Tuscaloosa; United States Department of Energy (DOE); Argonne National Laboratory; Centre National de la Recherche Scientifique (CNRS); CNRS - National Institute of Nuclear and Particle Physics (IN2P3); UDICE-French Research Universities; Universite PSL; Universite Paris Cite; Observatoire de Paris; CEA; Centro Brasileiro de Pesquisas Fisicas; University of Chicago; Centro de Investigaciones Energeticas, Medioambientales Tecnologicas; Columbia University; University of California System; University of California Davis; Drexel University; Hiroshima Institute of Technology; Illinois Institute of Technology; Russian Academy of Sciences; Institute for Nuclear Research of the Russian Academy of Sciences; Kansas State University; Kobe University; National Research Centre - Kurchatov Institute; Massachusetts Institute of Technology (MIT); Max Planck Society; Niigata University; University of Notre Dame; Universites de Strasbourg Etablissements Associes; Universite de Strasbourg; IMT - Institut Mines-Telecom; IMT Atlantique; Nantes Universite; Technical University of Munich; University of Tennessee System; University of Tennessee Knoxville; Tohoku University; Tohoku Gakuin University; Tokyo Institute of Technology; Tokyo Metropolitan University; Eberhard Karls University of Tubingen; Universidade Federal do ABC (UFABC); Universidade Estadual de Campinas; Virginia Polytechnic Institute & State UniversityThe 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 \(\theta_{13}\) 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 \(\theta_{13}\) 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\(\theta_{13}\))=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 \(\theta_{13}\) that does not depend on a background model.Item Erratum to: Improved measurements of the neutrino mixing angle θ_13 with the Double Chooz detector(2015) Double Chooz Collaboration; Busenitz, J.; Elnimr, M.; Fernandes, S.M.; Reichenbacher, J.; Stancu, I.; Sun, Y.; University of Alabama TuscaloosaItem Improved measurements of the neutrino mixing angle θ_13 with the Double Chooz detector(2014) Double Chooz Collaboration; Busenitz, J.; Elnimr, M.; Fernandes, S.M.; Reichenbacher, J.; Stancu, I.; Sun, Y.; University of Alabama TuscaloosaThe Double Chooz experiment presents improved measurements of the neutrino mixing angle \(\theta_{13}\) using the data collected in 467.90 live days from a detector positioned at an average distance of 1050 m 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 \(\overline{\upsilon}_e\) signal has increased. The value of \(\theta_{13}\) is measured to be sin² 2 \(\theta_{13}\) = 0.090 − 0.029 + 0.032 from a fit to the observed energy spectrum. Deviations from the reactor \(\overline{\upsilon}_e\) prediction observed above a prompt signal energy of 4 MeV and possible explanations are also reported. A consistent value of \(\theta_{13}\) 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 \(\theta_{13}\) measurement despite the observed distortion.Item Measurement of θ_13 in Double Chooz using neutron captures on hydrogen with novel background rejection techniques(2016) Double Chooz Collaboration; Busenitz, J.; Fernandes, S.M.; Reichenbacher, J.; Stancu, I.; Sun, Y.; University of Alabama TuscaloosaThe Double Chooz collaboration presents a measurement of the neutrino mixing angle \(\theta_{13}\) using reactor \(\overline{\upsilon}_e\) observed via the inverse beta decay reaction in which the neutron is captured on hydrogen. This measurement is based on 462.72 live days data, approximately twice as much data as in the previous such analysis, collected with a detector positioned at an average distance of 1050 m from two reactor cores. Several novel techniques have been developed to achieve significant reductions of the backgrounds and systematic uncertainties. Accidental coincidences, the dominant background in this analysis, are suppressed by more than an order of magnitude with respect to our previous publication by a multi-variate analysis. These improvements demonstrate the capability of precise measurement of reactor \(\overline{\upsilon}_e\) without gadolinium loading. Spectral distortions from the \(\overline{\upsilon}_e\) reactor flux predictions previously reported with the neutron capture on gadolinium events are confirmed in the independent data sample presented here. A value of sin² 2\(\theta_{13}\) = \(0.095_{-0.039}^{+0.038}\)(stat+syst) is obtained from a fit to the observed event rate as a function of the reactor power, a method insensitive to the energy spectrum shape. A simultaneous fit of the hydrogen capture events and of the gadolinium capture events yields a measurement of sin² 2\(\theta_{13}\) = 0.088 ± 0.033(stat+syst).Item Ortho-positronium observation in the Double Chooz experiment(2014) Double Chooz Collaboration; Busenitz, J.; Elnimr, M.; Fernandes, S.M.; Reichenbacher, J.; Stancu, I.; Sun, Y.; University of Alabama TuscaloosaThe Double Chooz experiment measures the neutrino mixing angle \(\theta_{13}\) by detecting reactor \(\overline{\upsilon}_e\) via inverse beta decay. The positron-neutron space and time coincidence allows for a sizable background rejection, nonetheless liquid scintillator detectors would profit from a positron/electron discrimination, if feasible in large detector, to suppress the remaining background. Standard particle identification, based on particle dependent time profile of photon emission in liquid scintillator, can not be used given the identical mass of the two particles. However, the positron annihilation is sometimes delayed by the ortho-positronium (o-Ps) metastable state formation, which induces a pulse shape distortion that could be used for positron identification. In this paper we report on the first observation of positronium formation in a large liquid scintillator detector based on pulse shape analysis of single events. The o-Ps formation fraction and its lifetime were measured, finding the values of 44 % ±12 % (sys.) ±5 % (stat.) and 3.68 ns ±0.17 ns (sys.) ±0.15 ns (stat.) respectively, in agreement with the results obtained with a dedicated positron annihilation lifetime spectroscopy setup.Item Reactor rate modulation oscillation analysis with two detectors in Double Chooz(2021) Double Chooz Collaboration; Busenitz, J.; Reichenbacher, J.; Stancu, I.; Sun, Y.; University of Alabama TuscaloosaA \(\theta_{13}\) oscillation analysis based on the observed antineutrino rates at the Double Chooz far and near detectors for different reactor power conditions is presented. This approach provides a so far unique simultaneous determination of \(\theta_{13}\) and the total background rates without relying on any assumptions on the specific background contributions. The analysis comprises 865 days of data collected in both detectors with at least one reactor in operation. The oscillation results are enhanced by the use of 24.06 days (12.74 days) of reactor-off data in the far (near) detector. The analysis considers the \({\overline{\nu }}_{e}\) interactions up to a visible energy of 8.5 MeV, using the events at higher energies to build a cosmogenic background model considering fast-neutrons interactions and ⁹Li decays. The background-model-independent determination of the mixing angle yields sin²(2\(\theta_{13}\)) = 0.094 ± 0.017, being the best-fit total background rates fully consistent with the cosmogenic background model. A second oscillation analysis is also performed constraining the total background rates to the cosmogenic background estimates. While the central value is not significantly modified due to the consistency between the reactor-off data and the background estimates, the addition of the background model reduces the uncertainty on \(\theta_{13}\) to 0.015. Along with the oscillation results, the normalization of the anti-neutrino rate is measured with a precision of 0.86%, reducing the 1.43% uncertainty associated to the expectation.