Photo-Production of Charmed Particles By 19.5 Gev Gammas

Abstract

The photo-production experiment, BC 72/73, has been periodically running at SLAC since summer 1980. In this experiment, monochromatic gammas of 19.5 GeV are produced by the backward scattering of ultra violet laser beam of 0.266 μm into the 30 GeV SLED electron beam. Fig. 1 shows the measured energy spectrum of the gammas. It is seen that 85% of the beam are in E_γ > 15 GeV. The detection system, the SLAC Hybrid Facility is shown in Fig. 2. A high resolution camera (HRO) is installed in addition to the three normal cameras. The HRO has a spacial resolution of approximately 55 μm in the depth of ± 6 mm. The triggering of HRO for hadronic events are made by either the PWC-168E algorithm (delay 150 μs) or the lead glass wall signal (delay 1 μs). The triggering efficiency is estimated to be 90% for hadronic events and 80% for charm events.