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Register a new userOscSNS: A Precision Neutrino Oscillation Experiment at the SNS
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OscSNS Collaboration
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The growing evidence for short-baseline neutrino oscillations and the possible existence of sterile neutrinos necessitates the development of a cost-effective experiment that can resolve these mysteries. The OscSNS cite{1} experiment, located at the Spallation Neutron Source (SNS), Oak Ridge Laboratory, is ideal for this purpose.
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The project of a large underground experiment (NOE) devoted to long baseline neutrino oscillation measurement is presented. The apparatus is composed by calorimetric modules interleaved with TRD modules and has been optimized to be sensitive in the region of sin2 2theta and Dm2 suggested by the atmospheric neutrino oscillation signal.
The observation of the recent electron neutrino appearance in a muon neutrino beam and the high-precision measurement of the mixing angle $theta_{13}$ have led to a re-evaluation of the physics potential of the T2K long-baseline neutrino oscillation experiment. Sensitivities are explored for CP violation in neutrinos, non-maximal $sin^22theta_{23}$, the octant of $theta_{23}$, and the mass hierarchy, in addition to the measurements of $delta_{CP}$, $sin^2theta_{23}$, and $Delta m^2_{32}$, for various combinations of $ u$-mode and (bar{ u})-mode data-taking. With an exposure of $7.8times10^{21}$~protons-on-target, T2K can achieve 1-$sigma$ resolution of 0.050(0.054) on $sin^2theta_{23}$ and $0.040(0.045)times10^{-3}~rm{eV}^2$ on $Delta m^2_{32}$ for 100%(50%) neutrino beam mode running assuming $sin^2theta_{23}=0.5$ and $Delta m^2_{32} = 2.4times10^{-3}$ eV$^2$. T2K will have sensitivity to the CP-violating phase $delta_{rm{CP}}$ at 90% C.L. or better over a significant range. For example, if $sin^22theta_{23}$ is maximal (i.e $theta_{23}$=$45^circ$) the range is $-115^circ<delta_{rm{CP}}<-60^circ$ for normal hierarchy and $+50^circ<delta_{rm{CP}}<+130^circ$ for inverted hierarchy. When T2K data is combined with data from the NO$ u$A experiment, the region of oscillation parameter space where there is sensitivity to observe a non-zero $delta_{CP}$ is substantially increased compared to if each experiment is analyzed alone.
The $ uebar$ flux and spectrum have been measured at a distance of about 800 m from the reactors of the Palo Verde Nuclear Generating Station using a segmented Gd-loaded liquid scintillator detector. Correlated positron-neutron events from the reaction $ uebar$p$to$e^+n were recorded for a period of 200 d including 55 d with one of the three reactors off for refueling. Backgrounds were accounted for by making use of the reactor-on and reactor-off cycles, and also with a novel technique based on the difference between signal and background under reversal of the e^+ and n portions of the events. A detailed description of the detector calibration, background subtraction, and data analysis is presented here. Results from the experiment show no evidence for neutrino oscillations. $ uebartobar u_x$ oscillations were excluded at 90% CL for $dm>1.12times10^{-3}$ eV^2 for full mixing, and $sinq>0.21$ for large $dm$. These results support the conclusion that the observed atmospheric neutrino oscillations does not involve $ u_{rm e}$.
The last unknown neutrino mixing angle $theta_{13}$ is one of the fundamental parameters of nature; it is also a crucial parameter for determining the sensitivity of future long-baseline experiments aimed to study CP violation in the neutrino sector. Daya Bay is a reactor neutrino oscillation experiment designed to achieve a sensitivity on the value of $sin^2(2theta_{13})$ to better than 0.01 at 90% CL. The experiment consists of multiple identical detectors placed underground at different baselines to minimize systematic errors and suppress cosmogenic backgrounds. With the baseline design, the expected anti-neutrino signal at the far site is about 360 events per day and at each of the near sites is about 1500 events per day. An overview and current status of the experiment will be presented.
The analysis and results are presented from the complete data set recorded at Palo Verde between September 1998 and July 2000. In the experiment, the $ uebar$ interaction rate has been measured at a distance of 750 and 890 m from the reactors of the Palo Verde Nuclear Generating Station for a total of 350 days, including 108 days with one of the three reactors off for refueling. Backgrounds were determined by (a) the $swap$ technique based on the difference between signal and background under reversal of the positron and neutron parts of the correlated event and (b) making use of the conventional reactor-on and reactor-off cycles. There is no evidence for neutrino oscillation and the mode $ uebartobar u_x$ was excluded at 90% CL for $dm>1.1times10^{-3}$ eV$^2$ at full mixing, and $sinq>0.17$ at large $dm$.
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