Browsing by Author "Cheng, J. H."

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Measurement of the Reactor Antineutrino Flux and Spectrum at Daya Bay
(2016-02-12)
An, F. P.
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Balantekin, A. B.
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Band, H. R.
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Bishai, M.
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Blyth, S.
This Letter reports a measurement of the flux and energy spectrum of electron antineutrinos from six 2.9 GW(th) nuclear reactors with six detectors deployed in two near (effective baselines 512 and 561 m) and one far (1579 m) underground experimental halls in the Daya Bay experiment. Using 217 days of data, 296 721 and 41 589 inverse beta decay (IBD) candidates were detected in the near and far halls, respectively. The measured IBD yield is (1.55 +/- 0.04) x 10(-18) cm(2) GW(-1) day(-1) or (5.92 +/- 0.14) x 10(-43) cm(2) fission(-1). This flux measurement is consistent with previous short-baseline reactor antineutrino experiments and is 0.946 +/- 0.022 (0.991 +/- 0.023) relative to the flux predicted with the Huber-Mueller (ILL-Vogel) fissile antineutrino model. The measured IBD positron energy spectrum deviates from both spectral predictions by more than 2 sigma over the full energy range with a local significance of up to similar to 4 sigma between 4-6 MeV. A reactor antineutrino spectrum of IBD reactions is extracted from the measured positron energy spectrum for model-independent predictions.
New Measurement of Antineutrino Oscillation with the Full Detector Configuration at Daya Bay
(2015-09-11)
An, F. P.
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Balantekin, A. B.
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Band, H. R.
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Bishai, M.
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Blyth, S.
We report a new measurement of electron antineutrino disappearance using the fully constructed Daya Bay Reactor Neutrino Experiment. The final two of eight antineutrino detectors were installed in the summer of 2012. Including the 404 days of data collected from October 2012 to November 2013 resulted in a total exposure of 6.9 x 10(5) GW(th) ton days, a 3.6 times increase over our previous results. Improvements in energy calibration limited variations between detectors to 0.2%. Removal of six Am-241-C-13 radioactive calibration sources reduced the background by a factor of 2 for the detectors in the experimental hall furthest from the reactors. Direct prediction of the antineutrino signal in the far detectors based on the measurements in the near detectors explicitly minimized the dependence of the measurement on models of reactor antineutrino emission. The uncertainties in our estimates of sin(2)2 theta(13) and vertical bar Delta m(ee)(2)vertical bar were halved as a result of these improvements. An analysis of the relative antineutrino rates and energy spectra between detectors gave sin(2)2 theta(13) = 0.084 +/- 0.005 and vertical bar Delta m(ee)(2)vertical bar = (2.42 +/- 0.11) x 10(-3) eV(2) in the three-neutrino framework.
New measurement of theta(13) via neutron capture on hydrogen at Daya Bay
(2016-04-21)
An, F. P.
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Balantekin, A. B.
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Band, H. R.
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Bishai, M.
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Blyth, S.
This article reports an improved independent measurement of neutrino mixing angle theta(13) at the Daya Bay Reactor Neutrino Experiment. Electron antineutrinos were identified by inverse beta-decays with the emitted neutron captured by hydrogen, yielding a data set with principally distinct uncertainties from that with neutrons captured by gadolinium. With the final two of eight antineutrino detectors installed, this study used 621 days of data including the previously reported 217-day data set with six detectors. The dominant statistical uncertainty was reduced by 49%. Intensive studies of the cosmogenic muon-induced Li-9 and fast neutron backgrounds and the neutron-capture energy selection efficiency, resulted in a reduction of the systematic uncertainty by 26%. The deficit in the detected number of antineutrinos at the far detectors relative to the expected number based on the near detectors yielded sin(2)2 theta(13) = 0.071 +/- 0.011 in the three-neutrino-oscillation framework. The combination of this result with the gadolinium-capture result is also reported.
The detector system of the Daya Bay reactor neutrino experiment
(2016-03-01)
An, F. P.
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Bai, J. Z.
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Balantekin, A. B.
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Band, H. R.
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Beavis, D.
The Daya Bay experiment was the first to report simultaneous measurements of reactor antineutrinos at multiple baselines leading to the discovery of (nu) over bar (e) oscillations over km-baselines. Subsequent data has provided the world\'s most precise measurement of sin 2 2013 and the effective mass splitting Delta m(ee)(2). The experiment is located in Daya Bay, China where the cluster of six nuclear reactors is among the world\'s most prolific sources of electron antineutrinos. Multiple antineutrino detectors are deployed in three underground water pools at different distances from the reactor cores to search for deviations in the antineutrino rate and energy spectrum due to neutrino mixing. Instrumented with photomultiplier tubes, the water pools serve as shielding against natural radioactivity from the surrounding rock and provide efficient muon tagging. Arrays of resistive plate chambers over the top of each pool provide additional muon detection. The antineutrino detectors were specifically designed for measurements of the antineutrino flux with minimal systematic uncertainty. Relative detector efficiencies between the near and far detectors are known to better than 0.2%. With the unblinding of the final two detectors\' baselines and target masses, a complete description and comparison of the eight antineutrino detectors can now be presented. This paper describes the Daya Bay detector systems, consisting of eight antineutrino detectors in three instrumented water pools in three underground halls, and their operation through the first year of eight detector data-taking. (C) 2015 Elsevier B.V. All rights reserved.