Contributions of Cherenkov Light to the Signals from Lead Tungstate Crystals

Results are presented of detailed measurements of the signals generated by high-energy electrons and muons in lead tungstate crystals. A significant fraction of the light produced in these crystals and detected by photomultiplier tubes is the result of the \v{C}erenkov mechanism. This is concluded from the angular dependence of the signals and from their time structure. Depending on the orientation of the crystals and on the particle type, \v{C}erenkov light may account for up to 15% of the total signals.