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. ${\overline{\nu }}_e-{\overline{\nu }}_x$ oscillations with $\Delta m^2>1.12\mathrm{}\times {10}^{-3\mathrm{}}{\mathrm{eV}}^2$ for maximal mixing and ${sin}^{2}2\theta >0.21\mathrm{}$ for large $\Delta m^2$. Our results support the conclusion that the atmospheric neutrino oscillations observed by Super-Kamiokande do not involve ${\nu }_e$.