Browsing by Author "Lin, G. L."

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A high precision calibration of the nonlinear energy response at Daya Bay
(2019-10-01)
Adey, D.
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An, F. P.
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Balantekin, A. B.
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Band, H. R.
;
Bishai, M.
A high precision calibration of the nonlinearity in the energy response of the Daya Bay Reactor Neutrino Experiment's antineutrino detectors is presented in detail. The energy nonlinearity originates from the particle-dependent light yield of the scintillator and charge-dependent electronics response. The nonlinearity model is constrained by.. calibration points from deployed and naturally occurring radioactive sources, the.. spectrum from B-12 decays, and a direct measurement of the electronics nonlinearity with a new flash analog-to-digital converter readout system. Less than 0.5% uncertainty in the energy nonlinearity calibration is achieved for positrons of kinetic energies greater than 1 MeV.
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."
An apparatus for studying spallation neutrons in the Aberdeen Tunnel laboratory
(2013-09-21)
Blyth, S. C.
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Chan, Y. L.
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Chen, X. C.
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Ch, M. C.
;
Hahn, R. L.
In this paper, we describe the design, construction and performance of an apparatus installed in the Aberdeen Tunnel laboratory in Hong Kong for studying spallation neutrons induced by cosmic-ray muons under a vertical rock overburden of 611 m water equivalent (m.w.e.). The apparatus comprises six horizontal layers of plastic-scintillator hodoscopes for determining the direction and position of the incident cosmic-ray muons. Sandwiched between the hodoscope planes is a neutron detector filled with 650 kg of liquid scintillator doped with about 0.06% of Gadolinium by weight for improving the efficiency of detecting the spallation neutrons. Performance of the apparatus is also presented. (C) 2013 Elsevier B.V. All rights reserved.
Cosmogenic neutron production at Daya Bay
(2018-03-26)
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.
Neutrons produced by cosmic ray muons are an important background for underground experiments studying neutrino oscillations, neutrinoless double beta decay, dark matter, and other rare-event signals. A measurement of the neutron yield in the three different experimental halls of the Daya Bay Reactor Neutrino Experiment at varying depth is reported. The neutron yield in Daya Bay's liquid scintillator is measured to be Y-n = (10.26 +/- 0.86) x 10(-5), (10.22 +/- 0.87) x 10(-5), and (17.03 +/- 1.22) x 10(-5) mu(-1)g(-1)cm(2) at depths of 250, 265, and 860 meters-water-equivalent. These results are compared to other measurements and the simulated neutron yield in FLUKA and GEANT4. A global fit including the Daya Bay measurements yields a power law coefficient of 0.77 +/- 0.03 for the dependence of the neutron yield on muon energy.
Evolution of the Reactor Antineutrino Flux and Spectrum at Daya Bay
(2017-06-19)
An, F. P.
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Balantekin, A. B.
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Band, H. R.
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Bishai, M.
;
Blyth, S.
The Daya Bay experiment has observed correlations between reactor core fuel evolution and changes in the reactor antineutrino flux and energy spectrum. Four antineutrino detectors in two experimental halls were used to identify 2.2 million inverse beta decays (IBDs) over 1230 days spanning multiple fuel cycles for each of six 2.9 GW(th) reactor cores at the Daya Bay and Ling Ao nuclear power plants. Using detector data spanning effective Pu-239 fission fractions F-239 from 0.25 to 0.35, Daya Bay measures an average IBD yield (sigma) over bar (f) of (5.90 +/- 0.13) x 10(-43) cm(2)/fission and a fuel-dependent variation in the IBD yield, d sigma(f)/dF(239), of (-1.86 +/- 0.18) x 10(-43) cm(2)/fission. This observation rejects the hypothesis of a constant antineutrino flux as a function of the Pu-239 fission fraction at 10 standard deviations. The variation in IBD yield is found to be energy dependent, rejecting the hypothesis of a constant antineutrino energy spectrum at 5.1 standard deviations. While measurements of the evolution in the IBD spectrum show general agreement with predictions from recent reactor models, the measured evolution in total IBD yield disagrees with recent predictions at 3.1 sigma. This discrepancy indicates that an overall deficit in the measured flux with respect to predictions does not result from equal fractional deficits from the primary fission isotopes U-235, Pu-239, U-238, and Pu-241. Based on measured IBD yield variations, yields of (6.17 +/- 0.17) and (4.27 +/- 0.26) x 10(-43) cm(2)/fission have been determined for the two dominant fission parent isotopes U-235 and Pu-239. A 7.8% discrepancy between the observed and predicted U-235 yields suggests that this isotope may be the primary contributor to the reactor antineutrino anomaly.
Extraction of the U-235 and Pu-239 Antineutrino Spectra at Daya Bay
(2019-09-13)
Adey, D.
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An, F. P.
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Balantekin, A. B.
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Band, H. R.
;
Bishai, M.
This Letter reports the first extraction of individual antineutrino spectra from U-235 and Pu-239 fission and an improved measurement of the prompt energy spectrum of reactor antineutrinos at Daya Bay. The analysis uses 3.5 x 10(6) inverse beta-decay candidates in four near antineutrino detectors in 1958 days. The individual antineutrino spectra of the two dominant isotopes, U-235 and Pu-239, are extracted using the evolution of the prompt spectrum as a function of the isotope fission fractions. In the energy window of 4-6 MeV, a 7% (9%) excess of events is observed for the U-235 (Pu-239) spectrum compared with the normalized Huber-Mueller model prediction. The significance of discrepancy is 4.0 sigma for U-235 spectral shape compared with the Huber-Mueller model prediction. The shape of the measured inverse beta-decay prompt energy spectrum disagrees with the prediction of the Huber-Mueller model at 5.3 sigma. In the energy range of 4-6 MeV, a maximal local discrepancy of 6.3 sigma is observed.
FLASH-TW experiment status report
(2005)
Liu, T. C.
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Chang, F. Y.
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Chen, C. C.
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Chen, C. W.
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Huang, M. A.
FLASH-TW is an experiment to measure the shower lateral and longitudinal profiles. We perform the shower profile measurement by shooting the 1.5 GeV electron beams in NSRRC on targets made of 15 aluminum blocks, each with a thickness of 2.9 cm. A scintillator (Al2O3: Cr)) is placed behind the targets, converting the secondary shower particles into light. The light from the central region of the shower is recorded by a CCD camera while the light from the outer region is monitored by PMTs. The CCD system is successfully implemented in the run 2 and run 3 of experiment FLASH at SLAC. A test run of the current experiment has been conducted in NSRRC in the past June to study the scintillator spectrum. Two more runs are planned from now to the year 2006 to measure the shower lateral and longitudinal profiles.
Improved Constraints on Sterile Neutrino Mixing from Disappearance Searches in the MINOS, MINOS+, Daya Bay, and Bugey-3 Experiments
(2020-08-10)
Adamson, P.
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An, F. P.
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Anghel, I.
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Aurisano, A.
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Balantekin, A. B.
Searches for electron antineutrino, muon neutrino, and muon antineutrino disappearance driven by sterile neutrino mixing have been carried out by the Daya Bay and MINOS+ collaborations. This Letter presents the combined results of these searches, along with exclusion results from the Bugey-3 reactor experiment, framed in a minimally extended four-neutrino scenario. Significantly improved constraints on the theta(mu e) mixing angle are derived that constitute the most constraining limits to date over five orders of magnitude in the mass-squared splitting Delta m(41)(2), excluding the 90% C.L. sterile-neutrino parameter space allowed by the LSND and MiniBooNE observations at 90% CLs for Delta m(41)(2) < 13 eV(2). Furthermore, the LSND and MiniBooNE 99% C.L. allowed regions are excluded at 99% CLs for Delta m(41)(2) < 1.6 eV(2).
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.
;
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.
Improved measurement of the reactor antineutrino flux and spectrum at Daya Bay
(2017-01)
An, F. P.
;
Balantekin, A. B.
;
Band, H. R.
;
Bishai, M.
;
Blyth, S.
A new measurement of the reactor antineutrino flux and energy spectrum by the Daya Bay reactor neutrino experiment is reported. The antineutrinos were generated by six 2.9 GW(th) nuclear reactors and detected by eight antineutrino detectors deployed in two near (560 m and 600 m flux-weighted baselines) and one far (1640 m flux-weighted baseline) underground experimental halls. With 621 days of data, more than 1.2 million inverse beta decay (IBD) candidates were detected. The IBD yield in the eight detectors was measured, and the ratio of measured to predicted flux was found to be 0.946 +/- 0.020 (0.992 +/- 0.021) for the Huber+Mueller (ILL+Vogel) model. A 2.9 sigma deviation was found in the measured IBD positron energy spectrum compared to the predictions. In particular, an excess of events in the region of 4-6 MeV was found in the measured spectrum, with a local significance of 4.4 sigma. A reactor antineutrino spectrum weighted by the IBD cross section is extracted for model-independent predictions.
Improved measurement of the reactor antineutrino flux and spectrum at Daya Bay
(2017-01-01)
An, F. P.
;
Balantekin, A. B.
;
Band, H. R.
;
Bishai, M.
;
Blyth, S.
A new measurement of the reactor antineutrino flux and energy spectrum by the Daya Bay reactor neutrino experiment is reported. The antineutrinos were generated by six 2.9 GW(th) nuclear reactors and detected by eight antineutrino detectors deployed in two near (560 m and 600 m flux-weighted baselines) and one far (1640 m flux-weighted baseline) underground experimental halls. With 621 days of data, more than 1.2 million inverse beta decay (IBD) candidates were detected. The IBD yield in the eight detectors was measured, and the ratio of measured to predicted flux was found to be 0.946 +/- 0.020 (0.992 +/- 0.021) for the Huber+Mueller (ILL+Vogel) model. A 2.9 sigma deviation was found in the measured IBD positron energy spectrum compared to the predictions. In particular, an excess of events in the region of 4-6 MeV was found in the measured spectrum, with a local significance of 4.4 sigma. A reactor antineutrino spectrum weighted by the IBD cross section is extracted for model-independent predictions.
Improved measurement of the reactor antineutrino flux at Daya Bay
(2019-09-09)
Adey, D.
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An, F. P.
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Balantekin, A. B.
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Band, H. R.
;
Bishai, M.
This work reports a precise measurement of the reactor antineutrino flux using 2.2 million inverse beta decay (IBD) events collected with the Daya Bay near detectors in 1230 days. The dominant uncertainty on the neutron detection efficiency is reduced by 56% with respect to the previous measurement through a comprehensive neutron calibration and detailed data and simulation analysis. The new average IBD yield is determined to be (5.91 +/- 0.09) x 10(-43) cm(2)/fission with total uncertainty improved by 29%. The corresponding mean fission fractions from the four main fission isotopes U-235, U-238, Pu-239, and( 241)Pu are 0.564, 0.076, 0.304, and 0.056, respectively. The ratio of measured to predicted antineutrino yield is found to be 0.952 +/- 0.014 +/- 0.023 (1.001 +/- 0.015 +/- 0.027) for the Huber-Mueller (ILL-Vogel) model, where the first and second uncertainty are experimental and theoretical model uncertainty, respectively. This measurement confirms the discrepancy between the world average of reactor antineutrino flux and the Huber-Mueller model.
Improved Search for a Light Sterile Neutrino with the Full Configuration of the Daya Bay Experiment
(2016-10-07)
An, F. P.
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Balantekin, A. B.
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Band, H. R.
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Bishai, M.
;
Blyth, S.
This Letter reports an improved search for light sterile neutrino mixing in the electron antineutrino disappearance channel with the full configuration of the Daya Bay Reactor Neutrino Experiment. With an additional 404 days of data collected in eight antineutrino detectors, this search benefits from 3.6 times the statistics available to the previous publication, as well as from improvements in energy calibration and background reduction. A relative comparison of the rate and energy spectrum of reactor antineutrinos in the three experimental halls yields no evidence of sterile neutrino mixing in the 2 x 10(-4) less than or similar to vertical bar Delta m(41)(2)vertical bar less than or similar to 0.3 eV(2) mass range. The resulting limits on sin(2) 2 theta(14) are improved by approx imately a factor of 2 over previous results and constitute the most stringent constraints to date in the vertical bar Delta m(41)(2)vertical bar less than or similar to 0.2 eV(2) region.
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.
Limits on Active to Sterile Neutrino Oscillations from Disappearance Searches in the MINOS, Daya Bay, and Bugey-3 Experiments
(2016-10-07)
Adamson, P.
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An, F. P.
;
Anghel, I.
;
Aurisano, A.
;
Balantekin, A. B.
Searches for a light sterile neutrino have been performed independently by the MINOS and the Daya Bay experiments using the muon (anti) neutrino and electron antineutrino disappearance channels, respectively. In this Letter, results from both experiments are combined with those from the Bugey-3 reactor neutrino experiment to constrain oscillations into light sterile neutrinos. The three experiments are sensitive to complementary regions of parameter space, enabling the combined analysis to probe regions allowed by the Liquid Scintillator Neutrino Detector (LSND) and MiniBooNE experiments in a minimally extended four-neutrino flavor framework. Stringent limits on sin(2) 2 theta(mu e) are set over 6 orders of magnitude in the sterile mass-squared splitting Delta m(41)(2). The sterile-neutrino mixing phase space allowed by the LSND and MiniBooNE experiments is excluded for Delta m(41)(2) < 0.8 eV(2) at 95% CLs.
Measurement of Cosmic-ray Muon-induced Spallation Neutrons in the Aberdeen Tunnel Underground Laboratory
(2016-04-01)
Blyth, S. C.
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Chan, Y. L.
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Chen, X. C.
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Chu, M. C.
;
Cui, K. X.
Muon-induced neutrons are one of the major backgrounds to various underground experiments, such as dark matter searches, low-energy neutrino oscillation experiments and neutrino-less double beta-decay experiments. Previous experiments on the underground production rate of muon-induced neutrons were mostly carried out either at shallow sites or at very deep sites. The Aberdeen Tunnel experiment aims to measure the neutron production rate at a moderate depth of 611 meters water equivalent. Our apparatus comprises of six layers of plastic-scintillator hodoscopes for tracking the incident cosmic-ray muons, and 760 L of gadolinium-doped liquid-scintillator for both neutron production and detection targets. In this paper, we describe the design and the performance of the apparatus. The preliminary result on the measurement of neutron production rate is also presented.
Measurement of Cosmic-ray Muon-induced Spallation Neutrons in the Aberdeen Tunnel Underground Laboratory
(2016-04-06)
Blyth, S. C.
;
Chan, Y. L.
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Chen, X. C.
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Chu, M. C.
;
Cui, K. X.
Muon-induced neutrons are one of the major backgrounds to various underground experiments, such as dark matter searches, low-energy neutrino oscillation experiments and neutrino-less double beta-decay experiments. Previous experiments on the underground production rate of muon-induced neutrons were mostly carried out either at shallow sites or at very deep sites. The Aberdeen Tunnel experiment aims to measure the neutron production rate at a moderate depth of 611 meters water equivalent. Our apparatus comprises of six layers of plastic-scintillator hodoscopes for tracking the incident cosmic-ray muons, and 760 L of gadolinium-doped liquid-scintillator for both neutron production and detection targets. In this paper, we describe the design and the performance of the apparatus. The preliminary result on the measurement of neutron production rate is also presented.
Measurement of cosmic-ray muons and muon-induced neutrons in the Aberdeen Tunnel Underground Laboratory
(2016-04-07)
Blyth, S. C.
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Chan, Y. L.
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Chen, X. C.
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Chu, M. C.
;
Cui, K. X.
We have measured the muon flux and production rate of muon-induced neutrons at a depth of 611 m water equivalent. Our apparatus comprises three layers of crossed plastic scintillator hodoscopes for tracking the incident cosmic-ray muons and 760 L of a gadolinium-doped liquid scintillator for producing and detecting neutrons. The vertical muon intensity was measured to be I-mu = (5.7 +/- 0.6) x 10(-6) cm(-2) s(-1) sr(-1). The yield of muon-induced neutrons in the liquid scintillator was determined to be Y-n = (1.19 +/- 0.08(stat) +/- 0.21(syst)) x 10(-4) neutrons/(mu.g.cm(-2)). A fit to the recently measured neutron yields at different depths gave a mean muon energy dependence of < E-mu >(0.76 +/- 0.03) for liquid-scintillator targets.
Measurement of cosmic-ray muons and muon-induced neutrons in the Aberdeen Tunnel Underground Laboratory (vol 93, 072005, 2016)
(2016-11-28)
Blyth, S. C.
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Chan, Y. L.
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Chen, X. C.
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Chu, M. C.
;
Cui, K. X.
Measurement of electron antineutrino oscillation based on 1230 days of operation of the Daya Bay experiment
(2017-04-06)
An, F. P.
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Balantekin, A. B.
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Band, H. R.
;
Bishai, M.
;
Blyth, S.
A measurement of electron antineutrino oscillation by the Daya Bay Reactor Neutrino Experiment is described in detail. Six 2.9-GWth nuclear power reactors of the Daya Bay and Ling Ao nuclear power facilities served as intense sources of nu((e) over bar)'s. Comparison of the (v) over bare rate and energy spectrum measured by antineutrino detectors far from the nuclear reactors (similar to 1500-1950 m) relative to detectors near the reactors (similar to 350-600 m) allowed a precise measurement of (v) over bar (e) disappearance. More than 2.5 million (v) over bar (e) inverse beta-decay interactions were observed, based on the combination of 217 days of operation of six antineutrino detectors (December, 2011-July, 2012) with a subsequent 1013 days using the complete configuration of eight detectors (October, 2012-July, 2015). The (v) over bar (e) rate observed at the far detectors relative to the near detectors showed a significant deficit, R = 0.949 +/- 0.002(stat) +/- 0.002(syst). The energy dependence of (v) over bar (e) disappearance showed the distinct variation predicted by neutrino oscillation. Analysis using an approximation for the three-flavor oscillation probability yielded the flavor-mixing angle sin(2)2 theta(13) = 0.0841 +/- 0.0027(stat) +/- 0.0019(syst) and the effective neutrino mass-squared difference of broken vertical bar Delta m(ee)(2)vertical bar = (2.50 +/- 0.06(stat) +/- 0.06(syst)) x 10(-3) eV(2). Analysis using the exact three-flavor probability found Delta m(32)(2) = (2.45 +/- 0.06(stat) +/- 0.06d(syst)) x 10(-3) eV(2) assuming the normal neutrino mass hierarchy and Delta m(32)(2) = (-2.56 +/- 0.06(stat) +/- 0.06(syst)) x 10(-3) eV(2) for the inverted hierarchy.