A search for νμ→ντ oscillation

Abstract CHORUS is an experiment searching for ν μ →ν τ oscillation in the CERN wide band neutrino beam with a hybrid setup consisting of a nuclear emulsion target followed by electronic detectors. The experiment has been taking data from 1994 through 1997. A subset of the neutrino interactions collected in 1994 and 1995 have been analyzed, looking for ν τ charged current interactions where the τ lepton decays to μ ν μ ν τ . In a sample of 31,423 ν μ charged current interactions, no ν τ candidates were found. For large Δm 2 μ τ values, a limit on the mixing angle of sin 2 2 θ μτ −3 at 90% C.L. can be set, thus improving the previous best result.