Construction and performance of the L3 central tracking detector

Abstract The L3 central tracking detector has been in operation since the start-up of LEP ( Large Electron Positron collider) in 1989. This detector consists of a Time Expansion Chamber( TEC), a layer of Plastic Scintillating Fibers and a Z-chamber. The TECgives a high spatial resolution and an excellent multi-track reconstruction capability. The fibers are designed to calibrate the drift velocitywith high precision. The Z-Chamber provides TECwith accurate information about the z-coordinates of the tracks. A description of the design and the infrastructure of these three detectors, including the readout and data acquisition system, is given. The performance of the detectors during the 1990 and 1991 LEP running periods is presented.