Response of a PbWO4-scintillator array to electrons in the energy regime below 1 GeV

PbWO4 has been selected as the most appropriate scintillator material for future calorimeter projects at LHC to detect high energy photons in the multiple GeV range. In spite of the low yield of scintillation light, the applicability of the scintillator to detect photons and particles at energies well below 1 GeV has been studied using monoenergetic electrons between 180 and 855 MeV. The individual crystals (20x20x150mm(3)) are characterized by the optical quality and the response to low energy gamma-sources using hybrid photo diode tubes. The energy resolution of the EM-shower deposited by electrons in a 3x3 crystal matrix amounts to sigma/E=2.39%/root E+0.20% (E given in GeV). The obtained time resolution of sigma less than or equal to 130 ps allows photon/particle discrimination via time-of-flight measurement.