The Electromagnetic Calorimeter of the BTeV Experiment

BTeV is a new dedicated B-physics project at Fermilab. It requires excellent photon detection which is crucial to study CP violations in B decays and rare decays of B's to explore physics beyond the standard model. Electromagnetic calorimeter (EMCAL) built of lead tungstate (PbWO4) scintillating crystals can provide excellent energy and position resolution, compact shower size, fast signal, and reasonable radiation hardness.We have carried out beam studies of a prototype of the BTeV electromagnetic calorimeter. The test took place at the Institute for High Energy Physics, Protvino, Russia. The prototype was built of 25 PbWO4 crystals, from russian and chinese manufacturers. The results of the first set of measurements have confirmed the expected good energy and position resolution of the prototype, though revealed the fact that PbWO4 was not as radiation hard as expected when irradiated with intense high energy hadron and electron beams. The next step included additional studies of radiation hardness, methods of monitoring changes of crystal signal due to radiation using LEDs with different wavelength, and possible procedures for testing PbWO4 radiation hardness without high energy beams.