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}$.
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