Detection of monochromatic photons between 50 and 790 MeV with a PbWO/sub 4/-scintillator array

The performance of PbWO/sub 4/ as a fast and compact scintillator material for calorimetry at energies well below 1 GeV has been investigated using a collimated beam of monoenergetic photons with an energy between 50 and 790 MeV provided by the tagged photon facility of MAMI at Mainz. In continuation of previous experiments with electrons, a larger matrix of 5/spl times/5 PbWO/sub 4/-crystals (20/spl times/20/spl times/150-200 mm/sup 3/) has been used to reconstruct the electromagnetic shower. The scintillators were selected according to their optical quality and response to low energy /spl gamma/-sources. The array was operated at a stabilized temperature of T=8/spl deg/C and read-out individually by photomultiplier tubes. The achieved excellent energy resolution amounts to /spl sigma//E=1.54%//spl radic/E+0.30% (E given in GeV) and has proven the applicability of PbWO/sub 4/ as a high quality scintillator material even at medium energies. The experimental data have been reproduced by GEANT3 simulations.