The NA48 Liquid Krypton Calorimeter Description and Performances

The NA48 experiment at CERN aims at making a precision study of direct CP violation in the neutral kaons, by measuring $Re(\epsilon'/\epsilon)$ with an accuracy better than 0.02%. To achieve this goal, the experiment requires a neutral detector with fast response, high efficiency in a high-rate environment (\sim MHz), long-term stability, sub-nanosecond time resolution, millimetric space precision, and an excellent energy resolution (1%) in the $5 \to 100$ GeV range. To achieve these performances, a quasi-homogeneous Liquid Krypton calorimeter has been chosen, designed with a projective tower geometry, high transversal segmentation, and fast digital readout. The calorimeter was operative during the '97 data taking period, its performances were thoroughly studied, and found to be in agreement with design requirements. A detector description and performances analysis are here presented.