Chad Bryan Carter, Abilene Christian University / Brookhaven National Labratory 

Title: Veto Barrel Studies on the Crystal Ball Detector 

Abstract: E913/E914 are fixed target experiments running at the Brookhaven AGS using the Crystal Ball Detector to measure the properties of baryon resonance's through their neutral decay modes. The experiments utilize the Crystal Ball as a multi-photon spectrometer consisting of 672 NaI crystals that cover 96% of 4p steradians. The Veto Barrel is an array of four double ended curved scintillators that surround the beam pipe and are setup in anti-coincidence mode with the beam counters and crystals. Particular calibration studies were performed over a two month period, before the July 98 run, to understand better how to optimize operation of the scintillators. The studies also include a look at efficiencies of the Veto Barrel and different triggering mechanisms investigated including Analog Sum and Digital AND Triggering for the Veto Barrel. The Compton edge of a ¹³⁷Cs source, depositing approximately 0.5 MeV in the scintillator, was used as a calibration tool. Our efforts showed that there was an attenuation factor of 10 through the entire length of the 120cm, 5mm thick scintillators.