Results From The Palo Verde Neutrino Oscillation Experiment

The <(nu)over bar>(e) flux and spectrum have been measured at a distance of about 800 m from the reactors of the Pale Verde Nuclear Generating Station using a segmented Gd-loaded Liquid scintillator detector. Correlated positron-neutron events from the reaction <(nu)over bar>(e)p --> 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 ef 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. <(nu)over bar>(e) --><(nu)over bar>(x) oscillations were excluded at 90% C.L. for Delta m(2)>1.12x10(-3) eV(2) for full mixing and sin(2)2 theta>0.21 for large Delta m(2). These results support the conclusion that the observed atmospheric neutrino oscillations do not involve nu(e).