857 research outputs found
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
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
Plasmon-phonon coupling in large-area graphene dot and antidot arrays
Nanostructured graphene on SiO2 substrates pave the way for enhanced
light-matter interactions and explorations of strong plasmon-phonon
hybridization in the mid-infrared regime. Unprecedented large-area graphene
nanodot and antidot optical arrays are fabricated by nanosphere lithography,
with structural control down to the sub-100 nanometer regime. The interaction
between graphene plasmon modes and the substrate phonons is experimentally
demonstrated and structural control is used to map out the hybridization of
plasmons and phonons, showing coupling energies of the order 20 meV. Our
findings are further supported by theoretical calculations and numerical
simulations.Comment: 7 pages including 6 figures. Supporting information is available upon
request to author
JUNO Conceptual Design Report
The Jiangmen Underground Neutrino Observatory (JUNO) is proposed to determine
the neutrino mass hierarchy using an underground liquid scintillator detector.
It is located 53 km away from both Yangjiang and Taishan Nuclear Power Plants
in Guangdong, China. The experimental hall, spanning more than 50 meters, is
under a granite mountain of over 700 m overburden. Within six years of running,
the detection of reactor antineutrinos can resolve the neutrino mass hierarchy
at a confidence level of 3-4, and determine neutrino oscillation
parameters , , and to
an accuracy of better than 1%. The JUNO detector can be also used to study
terrestrial and extra-terrestrial neutrinos and new physics beyond the Standard
Model. The central detector contains 20,000 tons liquid scintillator with an
acrylic sphere of 35 m in diameter. 17,000 508-mm diameter PMTs with high
quantum efficiency provide 75% optical coverage. The current choice of
the liquid scintillator is: linear alkyl benzene (LAB) as the solvent, plus PPO
as the scintillation fluor and a wavelength-shifter (Bis-MSB). The number of
detected photoelectrons per MeV is larger than 1,100 and the energy resolution
is expected to be 3% at 1 MeV. The calibration system is designed to deploy
multiple sources to cover the entire energy range of reactor antineutrinos, and
to achieve a full-volume position coverage inside the detector. The veto system
is used for muon detection, muon induced background study and reduction. It
consists of a Water Cherenkov detector and a Top Tracker system. The readout
system, the detector control system and the offline system insure efficient and
stable data acquisition and processing.Comment: 328 pages, 211 figure
A New Look at the Scalar Meson via Decays
Using of collision data collected with the
BESIII detector at the center-of-mass energy of 3.773 GeV, we investigate the
semileptonic decays ( and ).
The decay is observed for the first time. By
analyzing simultaneously the differential decay rates of and in different
four-momentum transfer intervals, the product of the relevant hadronic form
factor and the magnitude of the
Cabibbo-Kobayashi-Maskawa matrix element is determined to be
for
the first time. With the input of from the global fit in the
standard model, we determine . The absolute branching fractions of and are determined as and . Combining these results with those of previous BESIII measurements on
their semielectronic counterparts from the same data sample, we test lepton
flavor universality by measuring the branching fraction ratios and , which are
compatible with the standard model expectation.Comment: Supplemental Materials added in this versio
Search for an axion-like particle in radiative decays
We search for an axion-like particle (ALP) through the process
, ,
in a data sample with
events collected by the BESIII detector. No significant ALP signal
is observed over the expected background, and the upper limits on the branching
fraction of the decay and the ALP-photon coupling
constant are set at the 95\% confidence level in the mass
range of 0.165\leq m_a\leq2.84\,\mbox{GeV}/c^2. The limits on
range from to
over the search region, and the constraints on the
ALP-photon coupling are the most stringent to date for 0.165\leq
m_a\leq1.468\,\mbox{GeV}/c^2.Comment: 10 pages, 5 figure
Measurements of the branching fractions of the inclusive decays D0(D+)→π+π+π−X
Using eþe− annihilation data corresponding to an integrated luminosity of 2.93 fb−1 taken at a center-of mass energy of 3.773 GeV with the BESIII detector, we report the first measurements of the branching
fractions of the inclusive decays D0 → πþπþπ−X and Dþ → πþπþπ−X, where pions from K0
S decays have
been excluded from the πþπþπ− system and X denotes any possible particle combination. The branching
fractions of D0ðDþÞ → πþπþπ−X are determined to be BðD0 → πþπþπ−XÞ¼ð17.60 0.11 0.22Þ%
and BðDþ → πþπþπ−XÞ¼ð15.25 0.09 0.18Þ%, where the first uncertainties are statistical and the
second systematic
Measurements of the electric and magnetic form factors of the neutron for time-like momentum transfer
We present the first measurements of the electric and magnetic form factors
of the neutron in the time-like (positive ) region as function of
four-momentum transfer. We explored the differential cross sections of the
reaction with data collected with the BESIII
detector at the BEPCII accelerator, corresponding to an integrated luminosity
of 354.6 pb in total at twelve center-of-mass energies between GeV. A relative uncertainty of 18% and 12% for the electric and
magnetic form factors, respectively, is achieved at GeV.
Our results are comparable in accuracy to those from electron scattering in the
comparable space-like (negative ) region of four-momentum transfer. The
electromagnetic form factor ratio is within the
uncertainties close to unity. We compare our result on and to
recent model predictions, and the measurements in the space-like region to test
the analyticity of electromagnetic form factors.Comment: main paper: 9 pages, 6 figures, 3 tables; supplement: 9 pages, 28
table
Production of doubly-charged baryon in annihilation at energies from 2.3094 to 2.6464 GeV
The processes and
are studied for the first
time with of annihilation data collected with
the BESIII detector at center-of-mass energies from GeV to
GeV. No significant signal for the
process is observed and the upper limit of the Born cross section is estimated
at each energy point. For the process , a significant signal is observed at center-of-mass energies
near 2.6454 GeV and the corresponding Born cross section is reported.Comment: 10 pages, 4 figure
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