First application of the crystal PWO calorimeter as a mass spectrometer in high energy physics experiments under high counting rate conditions

A calorimeter based on lead tungstate heavy crystals (PWO) is tested during an experiment as part of GAMS-4π spectrometer. 50 thousand π0-mesons, produced in an intense π-beam with 32.5 GeV/s pulse are detected. A pure signal from π0 -> 2γ decay is distinguished regardless of a very high pion beam counting rate of the calorimeter cells. PWO spectrometer mass resolution measured is in a good agreement with previous testing using electron beams and calculations according to GEANT program. High accuracy of PWO spectrometer gauging in the real time is achieved using a signal coming from π0-meson. Results of these initial spectrometric testings in a beam demonstrate high qualities, typical of multicell PWO spectrometers during the detection of unstable particles which decay into photons