The performance of the NA48 detector

The NA48 experiment at the SPS accelerator at CERN aims at measuring the parameter of direct CP-violation, ε′/ε with an accuracy of 2×10−4. Neutral kaons are produced at two targets located at different distances from the detector, thus creating a “Klong” and a “Kshort” beam. The experiment measures the decays of kaons from these two beams into two neutral or two charged pions. tection of photons from neutral-pion decay is achieved by means of a liquid-krypton calorimeter. In order to suppress the huge background from KL0→3π0 decays, very good spatial, energy and time resolution are mandatory. The charged mode (K0L,S→π+π− decays) is measured with a spectrometer consisting of four drift chambers and a magnet. Decays from the two beams are distinguished by tagging the protons impinging on the second target by means of a scintillator array. Excellent time resolution and high efficiency are indispensible. Moreover, both the detector and the associated electronics operate in a high-radiation environment. This has given rise to specific problems, and the solutions adopted by NA48 are presented.