Comparison between high-energy proton and charged pion induced damage in PbWO4 calorimeter crystals

A PbWO4 crystal produced for the electromagnetic calorimeter of the CMS experiment at the LHC was cut into three equal-length sections. The central one was irradiated with 290MeV/c positive pions up to a fluence of (5.67±0.46)×1013cm-2, while the other two were exposed to a 24GeV/c proton fluence of (1.17±0.11)×1013cm-2. The damage recovery in these crystals, stored in the dark at room temperature, has been followed over two years. The comparison of the radiation-induced changes in light transmission for these crystals shows that damage is proportional to the star densities produced by the irradiation.