Here is a characteristic short decay. The tau neutrino, observed by its interaction in the steel layer which formed its lepton partner, is the fourth of the recorded tau events coming from the DONUT data set. The tau lepton decays to its daughter particle, the electron, in less than the distance it takes to traverse an emulsion layer. The secondary interaction vertex is captured in the emulsion data and the resulting single charged track identifies the event as tau. Again, the various views in different coordinate frames and distance scales help physicists to determine the interaction properties. In contrast to the first event shown, this electron was very high energy and was consequently observed in the EM Calorimeter. In the following picture the path of the electron was reconstructed through the detector using the spectrometer data. The high energy of the electron is evident by how far it penetrates and the readings from the calorimeter.

The first image is the passage of the electron through the emulsion sheets, indicated by the blue (steel) and yellow (emulsion and plastic) stripes. The adjacent image records the hits of the charged particle products through the scintillating fiber trackers which are positioned inbetween the emulsion modules. Below those two pictures is the reconstructed path of the particle through the entire emulsion and scintillating fiber target/detector. The last image is of the particle through the rest of the spectrometer: the analysis magnet, the drift chambers, the calorimeters and the muon identification dectector.

Last updated: 6/29/01 comment