A Search For $\nu_{\mu} \to \nu_{\tau}$ Oscillations In CHORUS

The CHORUS experiment is designed to search for $\nu_{\mu} \to \nu_{\tau}$ oscillations in the SPS Wide Band Neutrino Bearn at CERN. The design has been optimized to explore the $\Delta m^2$ region of cosmological interest in relation to the Dark Matter in a high $sin^2(2\theta)$ sensitivity. Data taking starting in April 1994 and finished in November 1997. A large subsample of neutrino interactions has already been analyzed searching for $\nu_{\tau}$ charged current interactions (CC) followed by $\tau$ decays into a muon or a single negative hadron. A sample of 133,616 interactions with an identified $\mu^-$ and 21,945 interactions without any identified muon have already been located. No $\nu_{\tau}$ candidate has been found. An upper limit on the oscillations probability of $P(\nu_{\mu} \to \nu_{\tau} \leq 4.0 x 10^{-4}$ can be set at 90% confidence level. Emulsion data taking is progressing, improving both the statistics and the $\tau$ decay finding efficiency. A sensitivity of $P(\nu_{\mu} \to \nu_{\tau} \leq 1.0 x 10^{-4}$ is expected to be achieved in the future.