Time of Flight Technique

At first glance, the traditional Time of Flight (TOF) technique for identification of pions, kaons and protons seems to be ideally suited for the momentum range of particles produced at the Tau-Charm Factory. In the decays of r leptons and charmed mesons most of the secondaries have momentum smaller then 1 GeV/c. The exception are the twoand three-body decays of $J and $’ where the region of interest extends to about 1.5 GeV/c. In the upper end of this momentum range the geometry of the detector will impose strict requirements on the necessary timing resolution. 1. Geometrical Considerations A typical TOF counter in a eSestorage ring experiment consists of a bar of _ plastic scint.illator placed at the outer radius of the tracking chamber and parallel to the beam axis. Light generated by the passage of charged particles is transmitted through the light guides to the photomultipliers placed in the region of low magnetic field usually outside the return yoke of the magnet[l].