The tagging detector of the CP-violation experiment NA48 at CERN

Abstract The CP-violation experiment NA48 at CERN aims at measuring direct CP-violation in the decays of neutral kaons into π + π − and π 0 π 0 . The experiment uses simultaneous, almost collinear beams of neutral K L 0 and K S 0 mesons, which are produced on two different targets. K S 0 events are “tagged” by measuring the times of the protons that fly towards the K S 0 production target. In order to sustain the high rate of 10 7  protons/s in this beam without suffering from too many pile-up events, the detector consists of 24 separate scintillators (12 horizontal and 12 vertical), each of which sees only a small fraction of the beam. Their signals are digitized by specially developed 1 G…