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 290 MeV/c positive pions up to a fluence of (5.67± 0.46)× 10 cm, while the other two were exposed to a 24 GeV/c proton fluence of (1.17 ± 0.11) × 10 cm. 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. submitted to Elsevier for publication in Nucl. Instr. and Meth. in Phys. Research A