Construction and beam test of a small compact electromagnetic PbWO4 calorimeter

Abstract A compact homogenous electromagnetic calorimeter with an energy resolution of better than 5%/ E/GeV , made out of lanthanum-doped lead tungstate crystals from Bogoroditsk, Russia, has been built for use in the ZEUS detector. The whole calorimeter, composed of 4×4 crystals, each of dimensions 23.8×23.8×200 mm 3 , light guides and photomultipliers, fits into a space of 12×12×27 cm 3 . Beam tests with electrons up to 100 GeV showed an energy resolution of better than 4.9%/ E/GeV , a linearity of better than 1% and a position resolution of 1.1 mm . The influence of temperature variations and recovery of an irradiated crystal on the total energy signal could be corrected to better than 1%. EGS4 simulations reproduce the results very well.