Present Status of $\nu_{\mu} \to \nu_{\tau}$ Oscillation Search in the CHORUS Experiment

The CHORUS experiment finished taking neutrino data at the end of 1997 after 4 years of nuclear emulsion exposure. In this period, 842.000 $v_µ$ CC events were recorded, out of which those obtained in the years 1994/95 have been preliminarily analysed. No candidate for $v_T$ interaction has been found. The resulting statistics gives a new limit for large $\Delta m^2$ at $sin^2 (2\theta)$ $\leq 2.3 10^{-3}$ with 90% C.L. It looks feasible, by adding the remaining data from 1996/97, to reach the proposed sensitivity of $sin^2 (2\theta)$ $\leq 2 · 10^{-4}$ (90% C.L.).