Latest results from the chorus neutrino oscillation experiment

The CHORUS experiment searches for vμ,→vτvμ,→vτ, oscillation looking for the T decay topology (with T flight length - 1 mm). The T is produced in a v, charged current interaction on an almost pure v,. beam. The hybrid detector is made of an emulsion target, combined with electronic detector. The target consists of - 800 kg of nuclear emulsion, the only detector with sufficient spatial resolution to reveal the r decay. The electronic apparatus reconstructs the tracks and predicts the zone where to look for the tracks in the emulsion; it is also used for the global event kinematics. In four years of data taking (1994-97) the CHORUS detector collected 456600 events with an identified µ and 116000 events with no µ identified in the final state. So far, 503 of these events have been analysed and located inside the emulsion. No T candidate has been found, giving a limit on the oscillation probability P,., < 4.6 · 10−410−4 at 90% C.L.