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Register a new userSpectral Measurement of the Electron Antineutrino Oscillation Amplitude and Frequency using 500 Live Days of RENO Data
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The Reactor Experiment for Neutrino Oscillation (RENO) has been taking electron antineutrino ($overline{ u}_{e}$) data from the reactors in Yonggwang, Korea, using two identical detectors since August 2011. Using roughly 500 live days of data through January 2013 we observe 290,775 (31,514) reactor $overline{ u}_{e}$ candidate events with 2.8 (4.9)% background in the near (far) detector. The observed visible positron spectra from the reactor $overline{ u}_{e}$ events in both detectors show discrepancy around 5 MeV with regard to the prediction from the current reactor $overline{ u}_{e}$ model. Based on a far-to-near ratio measurement using the spectral and rate information we have obtained $sin^2 2 theta_{13} = 0.082 pm 0.009({rm stat.}) pm 0.006({rm syst.})$ and $|Delta m_{ee}^2| =[2.62_{-0.23}^{+0.21}({rm stat.})_{-0.13}^{+0.12}({rm syst.})]times 10^{-3}$eV$^2$.
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The RENO experiment reports more precisely measured values of $theta_{13}$ and $|Delta m_{ee}^2|$ using $sim$2,200 live days of data. The amplitude and frequency of reactor electron antineutrino ($overline{ u}_e$) oscillation are measured by comparing the prompt signal spectra obtained from two identical near and far detectors. In the period between August 2011 and February 2018, the far (near) detector observed 103,212 (850,666) electron antineutrino candidate events with a background fraction of 4.7% (2.0%). A clear energy and baseline dependent disappearance of reactor $overline{ u}_e$ is observed in the deficit of the measured number of $overline{ u}_e$. Based on the measured far-to-near ratio of prompt spectra, we obtain $sin^2 2 theta_{13} = 0.0896 pm 0.0048({rm stat}) pm 0.0048({rm syst})$ and $|Delta m_{ee}^2| =[2.68 pm 0.12({rm stat}) pm 0.07({rm syst})]times 10^{-3}$~eV$^2$.
We present a neutrino oscillation analysis of two particular data sets from the Daya Bay and RENO reactor neutrino experiments aiming to study the increase in precision in the oscillation parameters $sin^2{2theta}_{13}$ and the effective mass splitting $Delta m^2_{ee}$ gained by combining two relatively simple to reproduce analyses available in the literature. For Daya Bay the data from 217 days between December 2011 and July 2012 were used. For RENO we used the data from 500 live days between August 2011 and January 2012. We reproduce reasonably well the results of the individual analyses, both, rate-only and spectral, defining a suitable $chi^2$ statistic for each case. Finally, we performed a combined spectral analysis and extract tighter constraints on the parameters, with an improved precision between 30-40% with respect of the individual analyses considered.
We report a measurement of electron antineutrino oscillation from the Daya Bay Reactor Neutrino Experiment with nearly 4 million reactor $overline{ u}_{e}$ inverse beta decay candidates observed over 1958 days of data collection. The installation of a Flash-ADC readout system and a special calibration campaign using different source enclosures reduce uncertainties in the absolute energy calibration to less than 0.5% for visible energies larger than 2 MeV. The uncertainty in the cosmogenic $^9$Li and $^8$He background is reduced from 45% to 30% in the near detectors. A detailed investigation of the spent nuclear fuel history improves its uncertainty from 100% to 30%. Analysis of the relative $overline{ u}_{e}$ rates and energy spectra among detectors yields $sin^{2}2theta_{13} = 0.0856pm 0.0029$ and $Delta m^2_{32}=(2.471^{+0.068}_{-0.070})times 10^{-3}~mathrm{eV}^2$ assuming the normal hierarchy, and $Delta m^2_{32}=-(2.575^{+0.068}_{-0.070})times 10^{-3}~mathrm{eV}^2$ assuming the inverted hierarchy.
A measurement of the energy dependence of antineutrino disappearance at the Daya Bay Reactor Neutrino Experiment is reported. Electron antineutrinos ($overline{ u}_{e}$) from six $2.9$ GW$_{rm th}$ reactors were detected with six detectors deployed in two near (effective baselines 512 m and 561 m) and one far (1579 m) underground experimental halls. Using 217 days of data, 41589 (203809 and 92912) antineutrino candidates were detected in the far hall (near halls). An improved measurement of the oscillation amplitude $sin^{2}2theta_{13} = 0.090^{+0.008}_{-0.009} $ and the first direct measurement of the $overline{ u}_{e}$ mass-squared difference $|Delta m^{2}_{ee}|= (2.59_{-0.20}^{+0.19}) times 10^{-3} {rm eV}^2 $ is obtained using the observed $overline{ u}_{e}$ rates and energy spectra in a three-neutrino framework. This value of $|Delta m^{2}_{ee}|$ is consistent with $|Delta m^{2}_{mumu}|$ measured by muon neutrino disappearance, supporting the three-flavor oscillation model.
The Reactor Experiment for Neutrino Oscillation (RENO) experiment has been taking data using two identical liquid scintillator detectors of 44.5 tons since August 2011. The experiment has observed the disappearance of reactor neutrinos in their interactions with free protons, followed by neutron capture on hydrogen. Based on 1500 live days of data taken with 16.8 GW$_{th}$ reactors at the Hanbit Nuclear Power Plant in Korea, the near (far) detector observes 567690 (90747) electron antineutrino candidate events with a delayed neutron capture on hydrogen. This provides an independent measurement of $theta_{13}$ and a consistency check on the validity of the result from n-Gd data. Furthermore, it provides an important cross-check on the systematic uncertainties of the n-Gd measurement. Based on a rate-only analysis, we obtain sin$^{2}$2$theta _{13}$= 0.087 $pm$ 0.008 (stat.) $pm$ 0.014 (syst.).
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