اشترك بالحزمة الذهبية واحصل على وصول غير محدود شمرا أكاديميا
تسجيل مستخدم جديدNeutrino oscillation analysis of 217 live-days of Daya Bay and 500 live-days of RENO
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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.
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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$^2$.
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.
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erline{ u}_{e}$s. Comparison of the $overline{ u}_{e}$ rate and energy spectrum measured by antineutrino detectors far from the nuclear reactors ($sim$1500-1950 m) relative to detectors near the reactors ($sim$350-600 m) allowed a precise measurement of $overline{ u}_{e}$ disappearance. More than 2.5 million $overline{ u}_{e}$ inverse beta decay interactions were observed, based on the combination of 217 days of operation of six antineutrino detectors (Dec. 2011--Jul. 2012) with a subsequent 1013 days using the complete configuration of eight detectors (Oct. 2012--Jul. 2015). The $overline{ u}_{e}$ rate observed at the far detectors relative to the near detectors showed a significant deficit, $R=0.949 pm 0.002(mathrm{stat.}) pm 0.002(mathrm{syst.})$. The energy dependence of $overline{ u}_{e}$ disappearance showed the distinct variation predicted by neutrino oscillation. Analysis using an approximation for the three-flavor oscillation probability yielded the flavor-mixing angle $sin^22theta_{13}=0.0841 pm 0.0027(mathrm{stat.}) pm 0.0019(mathrm{syst.})$ and the effective neutrino mass-squared difference of $left|{Delta}m^2_{mathrm{ee}}right|=(2.50 pm 0.06(mathrm{stat.}) pm 0.06(mathrm{syst.})) times 10^{-3} {rm eV}^2$. Analysis using the exact three-flavor probability found ${Delta}m^2_{32}=(2.45 pm 0.06(mathrm{stat.}) pm 0.06(mathrm{syst.})) times 10^{-3} {rm eV}^2$ assuming the normal neutrino mass hierarchy and ${Delta}m^2_{32}=(-2.56 pm 0.06(mathrm{stat.}) pm 0.06(mathrm{syst.})) times 10^{-3} {rm eV}^2$ for the inverted hierarchy.
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