Palo Verde 中子振荡实验的结果

The $\nuebar$ 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 $\nuebar$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. $\nuebar\to\bar\nu_x oscillations were excluded at 90$\dm>1.12\times10^{-3}$eV^2 for full mixing, and$\sinq>0.21$for large$\dm$. These results support the conclusion that the observed atmospheric neutrino oscillations does not involve$\nu_{\rm e}$.