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Register a new userNeutrino oscillation analysis of 217 live-days of Daya Bay and 500 live-days of RENO
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Alexis A. Aguilar-Arevalo Dr.
Publication date
2019
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English
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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.
A measurement of electron antineutrino oscillation by the Daya Bay Reactor Neutrino Experiment is described in detail. Six 2.9-GW$_{rm th}$ nuclear power reactors of the Daya Bay and Ling Ao nuclear power facilities served as intense sources of $overline{ u}_{e}$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.
We present results from the direct search for dark matter with the XENON100 detector, installed underground at the Laboratori Nazionali del Gran Sasso of INFN, Italy. XENON100 is a two-phase time projection chamber with a 62 kg liquid xenon target. Interaction vertex reconstruction in three dimensions with millimeter precision allows to select only the innermost 48 kg as ultra-low background fiducial target. In 100.9 live days of data, acquired between January and June 2010, no evidence for dark matter is found. Three candidate events were observed in a pre-defined signal region with an expected background of 1.8 +/- 0.6 events. This leads to the most stringent limit on dark matter interactions today, excluding spin-independent elastic WIMP-nucleon scattering cross-sections above 7.0x10^-45 cm^2 for a WIMP mass of 50 GeV/c^2 at 90% confidence level.
We report on a search for particle dark matter with the XENON100 experiment, operated at the Laboratori Nazionali del Gran Sasso (LNGS) for 13 months during 2011 and 2012. XENON100 features an ultra-low electromagnetic background of (5.3 pm 0.6) times 10^-3 events (kg day keVee)^-1 in the energy region of interest. A blind analysis of 224.6 live days times 34 kg exposure has yielded no evidence for dark matter interactions. The two candidate events observed in the pre-defined nuclear recoil energy range of 6.6-30.5 keVnr are consistent with the background expectation of (1.0 pm 0.2) events. A Profile Likelihood analysis using a 6.6-43.3 keVnr energy range sets the most stringent limit on the spin-independent elastic WIMP-nucleon scattering cross section for WIMP masses above 8 GeV/c^2, with a minimum of 2 times 10^-45 cm^2 at 55 GeV/c^2 and 90% confidence level.
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