4,151 research outputs found
Observation of electron-antineutrino disappearance at Daya Bay
The Daya Bay Reactor Neutrino Experiment has measured a non-zero value for
the neutrino mixing angle with a significance of 5.2 standard
deviations. Antineutrinos from six 2.9 GW 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_{\rm th}-day livetime exposure in 55 days, 10416 (80376) 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
. A rate-only analysis
finds in a
three-neutrino framework.Comment: 5 figures. Version to appear in Phys. Rev. Let
A side-by-side comparison of Daya Bay antineutrino detectors
The Daya Bay Reactor Neutrino Experiment is designed to determine precisely
the neutrino mixing angle with a sensitivity better than 0.01 in
the parameter sin 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 exceed requirements.Comment: 24 pages, 36 figure
A new measurement of antineutrino oscillation with the full detector configuration at Daya Bay
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 6.910 GW-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-C radioactive
calibration sources reduced the background by a factor of two 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
and were halved as a result of these
improvements. Analysis of the relative antineutrino rates and energy spectra
between detectors gave and eV in the three-neutrino
framework.Comment: Updated to match final published versio
New measurement of via neutron capture on hydrogen at Daya Bay
This article reports an improved independent measurement of neutrino mixing
angle at the Daya Bay Reactor Neutrino Experiment. Electron
antineutrinos were identified by inverse -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 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 in the
three-neutrino-oscillation framework. The combination of this result with the
gadolinium-capture result is also reported.Comment: 26 pages, 23 figure
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