Browsing by Author "Wang, L. S."

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A side-by-side comparison of Daya Bay antineutrino detectors
(1970-01-01)
An, F. P.
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An, Q.
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Bai, J. Z.
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Balantekin, A. B.
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Band, H. R.
"The Daya Bay Reactor Neutrino Experiment is designed to determine precisely the neutrino mixing angle theta(13) with a sensitivity better than 0.01 in the parameter sin(2) 2 theta(13) at the 90% confidence level. To achieve this goal, the collaboration will build eight functionally identical antineutrino detectors. The first two detectors have been constructed, installed and commissioned in Experimental Hall 1, with steady data-taking beginning September 23, 2011. A comparison of the data collected over the subsequent three months indicates that the detectors are functionally identical, and that detector-related systematic uncertainties are smaller than requirements. (C) 2012 Elsevier B.V. All rights reserved."
EELS plasmon studies of silver/carbon core/shell nanocables prepared by simple arc discharge
(2007-04-01)
Wang, L. S.
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Buchholz, D. B.
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Li, Y.
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Li, J.
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Lee, C. Y.
A method for the fabrication of large quantities of high quality silver nanocables encapsulated in carbon nanotubes (Ag@C) using a hydrogen arc is presented. A growth mechanism based on the generation of poly-aromatic hydrocarbons by the hydrogen arc is proposed. The size-dependent electronic structures of the resultant materials are investigated using electron energy loss spectroscopy (EELS). The surface plasmon and bulk-excitation character observed by EELS are discussed. As the diameter of Ag@C nanocable decreases, the surface and bulk plasmons of the silver core shift to lower energy and the peaks broaden. Measurements of electrical conductivity exhibits a liner current-voltage character with a conductivity of 0.5x10(4) S/cm for the nanocable structure.
Improved measurement of electron antineutrino disappearance at Daya Bay
(2013-01-01)
An, F. P.
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An, Q.
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Bai, J. Z.
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Balantekin, A. B.
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Band, H. R.
We report an improved measurement of the neutrino mixing angle theta(13) from the Daya Bay Reactor Neutrino Experiment. We exclude a zero value for sin(2)2 theta(13) with a significance of 7.7 standard deviations. Electron antineutrinos from six reactors of 2.9 GW(th) were detected in six antineutrino detectors deployed in two near (flux-weighted baselines of 470 m and 576 m) and one far (1648 m) underground experimental halls. Using 139 days of data, 28909 (205308) electron antineutrino candidates were detected at the far hall (near halls). The ratio of the observed to the expected number of antineutrinos assuming no oscillations at the far hall is 0.944 +/- 0.007(stat.)+/- 0.003(syst.). An analysis of the relative rates in six detectors finds sin(2)2 theta(13)= 0.089 +/- 0.010(stat.)+/- 0.005(syst.) in a three-neutrino framework.
Independent measurement of the neutrino mixing angle theta(13) via neutron capture on hydrogen at Daya Bay
(2014-10-03)
An, F. P.
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Balantekin, A. B.
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Band, H. R.
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Beriguete, W.
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Bishai, M.
A new measurement of the theta(13) mixing angle has been obtained at the Daya Bay Reactor Neutrino Experiment via the detection of inverse beta decays tagged by neutron capture on hydrogen. The antineutrino events for hydrogen capture are distinct from those for gadolinium capture with largely different systematic uncertainties, allowing a determination independent of the gadolinium-capture result and an improvement on the precision of the theta(13) measurement. With a 217-day antineutrino data set obtained with six antineutrino detectors and from six 2.9 GWth reactors, the rate deficit observed at the far hall is interpreted as sin(2)2 theta(13) = 0.083 +/- 0.018 in the three-flavor oscillation model. When combined with the gadolinium-capture result from Daya Bay, we obtain sin(2)2 theta(13) = 0.089 +/- 0.008 as the final result for the six-antineutrino-detector configuration of the Daya Bay experiment.
Observation of Electron-Antineutrino Disappearance at Daya Bay
(2012-04-23)
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 Reactor Neutrino Experiment has measured a nonzero value for the neutrino mixing angle 0(13) with a significance of 5.2 standard deviations. Antineutrinos from six 2.9 GW(th) reactors were detected in six antineutrino detectors deployed in two near (flux-weighted baseline 470 m and 576 m) and one far (1648 m) underground experimental halls. With a 43 000 ton-GW(th)-day live-time exposure in 55 days, 10 416 (80 376) electron-antineutrino candidates were detected at the far hall (near halls). The ratio of the observed to expected number of antineutrinos at the far hall is R = 0.940 +/- 0.011(stat.) +/- 0.004(syst.). A rate-only analysis finds sin(2)2 theta(13) = 0.092 +/- 0.016(stat.) +/- 0.005(syst.) in a three-neutrino framework.
Results from the Daya Bay Reactor Neutrino Experiment
(2014-01-01)
Tsang, K. V.
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An, F. P.
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An, Q.
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Bai, J. Z.
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Balantekin, A. B.
The Daya Bay Reactor Neutrino Experiment was designed to achieve a sensitivity on the value of sin(2) 2 theta(13). to better than 0.01 at 90% CL. The experiment consists of eight antineutrino detectors installed underground at different baselines from six nuclear reactors. With data collected with six antineutrino detectors for 55 days, Daya Bay announced the discovery of a non-zero value for sin(2) 2 theta(13) with a significance of 5.2 standard deviations in March 2012. The most recent analysis with 139 days of data acquired in a six-detector configuration yields sin(2) 2 theta(13) = 0.089 +/- 0.010(stat.) +/- 0.005(syst.), which is the most precise measurement of sin(2) 2 theta(13) to date.
Search for a Light Sterile Neutrino at Daya Bay
(2014-10-01)
An, F. P.
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Balantekin, A. B.
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Band, H. R.
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Beriguete, W.
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Bishai, M.
A search for light sterile neutrino mixing was performed with the first 217 days of data from the Daya Bay Reactor Antineutrino Experiment. The experiment's unique configuration of multiple baselines from six 2.9 GW(th) nuclear reactors to six antineutrino detectors deployed in two near (effective baselines 512 m and 561 m) and one far (1579 m) underground experimental halls makes it possible to test for oscillations to a fourth (sterile) neutrino in the 10(-3) eV(2) < vertical bar Delta m(41)(2)vertical bar < 0.3 eV(2) range. The relative spectral distortion due to the disappearance of electron antineutrinos was found to be consistent with that of the three-flavor oscillation model. The derived limits on sin(2) 2 theta(14) cover the 10(-3) eV(2) less than or similar to vertical bar Delta m(41)(2)vertical bar less than or similar to 0.1 eV(2) region, which was largely unexplored.
Spectral Measurement of Electron Antineutrino Oscillation Amplitude and Frequency at Daya Bay
(2014-02-10)
An, F. P.
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Balantekin, A. B.
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Band, H. R.
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Beriguete, W.
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Bishai, M.
A measurement of the energy dependence of antineutrino disappearance at the Daya Bay reactor neutrino experiment is reported. Electron antineutrinos ((v) over bar (e)) from six 2.9 GW(th) reactors were detected with six detectors deployed in two near (effective baselines 512 and 561 m) and one far (1579 m) underground experimental halls. Using 217 days of data, 41 589 (203 809 and 92 912) antineutrino candidates were detected in the far hall (near halls). An improved measurement of the oscillation amplitude sin(2) 2 theta(13) = 0.090(-0.009)(+0.008) and the first direct measurement of the (v) over bar (e) mass-squared difference vertical bar Delta m(ee)(2)vertical bar = (2.59(-0.20)(+0.19) x 10(-3) eV(2)) is obtained using the observed (v) over bar (e) rates and energy spectra in a three-neutrino framework. This value of vertical bar Delta m(ee)(2)vertical bar eejis consistent with vertical bar Delta m(mu mu)(2)vertical bar measured by muon neutrino disappearance, supporting the three-flavor oscillation model.
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.
The muon system of the Daya Bay Reactor antineutrino experiment
(2015-02-11)
An, F. P.
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Balantekin, A. B.
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Band, H. R.
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Beriguete, W.
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Bishai, M.
The Daya Bay experiment consists of functionally identical antineutrino detectors immersed in pools of ultrapure water in three well-separated underground experimental halls near two nuclear reactor complexes. These pools serve both as shields against natural, low-energy radiation, and as water Cherenkov detectors that efficiently detect cosmic muons using arrays of photomultiplier tubes. Each pool is covered by a plane of resistive plate chambers as an additional means of detecting muons. Design, construction, operation, and performance of these muon detectors are described. (C) 2014 Elsevier By. All rights reserved.