A PWO CRYSTALS CALORIMETER - FIRST APPLICATION FOR MASS-SPECTROMETRY IN A HIGH-ENERGY EXPERIMENT WITH A HIGH-LOAD

A calorimeter based on heavy crystals of lead tungstate (PWO) was expe rimentally tested as part of the Gamma AMC-4 pi spectrometer. A detect or exposed to an intense pi(0) beam with a momentum of 32.5 GeV/s extr acted from the 70-CeV proton accelerator at IHEP detected nearly 50 th ousand secondary pi(0) mesons, Despite a very high pi(-) load of the c alorimeter cells (reaching 10(6) pi(-) per second), a distinct pi(0) - -> 2 gamma signal was obtained. The observed massresolution of the PWO spectrometer is consistent with the results of calibration in electro n beams and with calculations performed using the GEANT program packag e. Using the observed pi(0)signal, we were able to calibrate the PWO s pectrometer with high precision in real time throughout the experiment al run, The results of these initial beam tests demonstrate high perfo rmance of the multicell PWO calorimeters in detecting radiative decays of unstable particles in a high-luminosity environment, as required b y future fixed-target and collider experiments.