Studies on high energy gamma trigger of lead-scintillating fiber electromagnetic calorimeter

The high flux of cosmic ray proton forms the main background of gamma ray detection experiments using a lead scintillating fiber sandwiched electromagnetic calorimeter. The trigger scheme is studied to efficiently detect high energy T-rays and reject most of the proton events. Efficient cuts are derived from the Monte Carlo analysis of electromagnetic shower shape in the calorimeter. Photons with energy above 10GeV are triggered at the level of 99%. The requirement of proton rate less than 100 Hz is also satisfied. The accuracy of the simulations is testified with the beam test.