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. νₑ-νₓ oscillations with Δm²>1.12×10^-3eV² for maximal mixing and sin²2θ>0.21 for large Δm². Our results support the conclusion that the atmospheric neutrino oscillations observed by Super-Kamiokande do not involve νₑ.