Search for $\nu_\mu \to \nu_\tau$ oscillation using the $\tau$ decay modes into a single charged particle

Part of the neutrino events collected in 1994-1995 by the CHORUS experiment has been analysed. A search was performed for $\nu_{\tau}$ charged current interactions followed by the $\tau$ lepton deca y into a single charged negative hadron, a possible indication for $\numtonut$ oscillation. A sample of 6,844 events without an identified muon has been located in the emulsion target. Within the s election criteria, no $\tau^-$ candidate has been found. Combining this result with the one from the search for $\nu_\tau$ interactions using the muonic decay mode (36,182 events with an identified muon), a 90\% C.L. limit on the mixing angle $\sin2t < 1.8\cdot 10^{-3}$ (at large $\Delta m^2$) has been derived.