Events in Delphi

Who dunnit? 1
Here two particles leave tracks in the wire chamber and deposit most of their energy in the dark grey blocks - the layer designed to reveal electrons and photons. As the particles leave tracks, they must be electrically charged. What do you think has happened? What particles have been created by the energy of the collision at the centre of the detectors?
(Remember, you can click on the image for a clearer view.)

c.sutton 26/9/97