Search for Neutrino Oscillations at the Palo Verde Nuclear Reactors

We report on the initial results from a measurement of the antineutrino flux and spectrum at a distance of about 800 m from the three reactors of the Palo Verde Nuclear Generating Station using a segmented gadolinium-loaded scintillation detector. We find that the antineutrino flux agrees with that predicted in the absence of oscillations excluding at 90% C. L. {}₄-{}ₗ oscillations with m^2>1. 1210^-3eV^2 for maximal mixing and sin^22>0. 21 for large m^2. Our results support the conclusion that the atmospheric neutrino oscillations observed by Super-Kamiokande do not involve ₄.