Limits on the neutrino oscillationsν¯μ→ν¯eandν¯μ→ν¯τusing a narrow-band beam

Abstract

In an exposure of the Fermilab 15-ft bubble chamber to the dichromatic antineutrino beam, 427 ${\overline{\nu }}_{\mu }$ charged-current interactions were obtained. Taking advantage of the small and well understood background flux of ${\overline{\nu }}_e\text{'}\mathrm{s}$ in the dichromatic ${\overline{\nu }}_{\mu }$ beam, upper limits on the rates of antineutrino oscillations are obtained, with the precision limited by statistical rather than systematic errors, in contrast to previous experiments. The 90%-C.L. upper limits obtained for the average oscillation probabilities indicated are $P({\overline{\nu }}_{\mu }\to {\overline{\nu }}_e)<\mathrm{}6.5\mathrm{}\times {10}^{-3\mathrm{}}$ and $P({\overline{\nu }}_{\mu }\to {\overline{\nu }}_{\tau })<\mathrm{}4.4\mathrm{}\times {10}^{-2\mathrm{}}$. The mean value of the distance from the neutrino-production point to the bubble chamber divided by the neutrino energy, $〈\frac{l}{E}〉$, is 0.03 m/MeV.