Physics: Geneva, Switzerland/CERN: L-3 Experiment. Computer simulation of particle physics collision. CERN is the European centre for particle physics near Geneva. L3 is one of 4 giant particle detectors at the LEP Collider. LEP collides electrons & positrons accelerated to an energy of 50 GeV in a circular tunnel 100m underground & 27km in circumference. L3 is a cylindrical assembly of many types of apparatus - hadron & electromagnetic calorimeters, drift chambers, & a time projection chamber - which fit together like layers of an onion around the point where the particles collide. L3 is a collaboration of 460 physicists from institutions in 13 countries.