Search for $\nu_{\mu}$($\nu_{e}$) <--> $\nu_{\tau}$ oscillations with a detector based on a emulsion-silicon target

We discuss the performance of a next generation $\osc$ oscillation experiment, based on a target consisting of a sandwich of nuclear emulsion layers and silicon detectors. The target would be followed by a full spectrometer for energy-momentum measurement and particle identification. A $\tau-$enriched sample is selected in terms of vertex and kinematical criteria using the electronic spectrometer, with very high efficiency, while at the same time reducing the load of background events to be scanned by up to two orders of magnitude. Events fulfilling the selection criteria are very efficiently located and scanned in the emulsion, thanks to the very good resolution allowed by the silicon tracker. In terms of the two-neutrino families mixing angle, this experiment could reach a sensitivity of $\sint < 1.1 \times 10^{-5}$ in an extended run at CERN and up to $\sint < 3.2 \times 10^{-6}$ at FNAL.