A 40 MHz-pipelined trigger for K0→2π0 decays for the CERN NA48 experiment

Abstract The “neutral” trigger system for the selection of K 0 →2π 0 →4γ decays of the NA48 CP-violation experiment is described. The trigger system has been implemented in a 40 MHz “dead-time free” pipeline to allow large rate reduction and high-trigger efficiency. The trigger decision is based on the information from 13 340 cells of the electro-magnetic calorimeter. Every 25 ns the energy, the centre of gravity, the kaon lifetime and the number of peaks in calorimeter projections are calculated in the trigger. The pipeline system is described and the performance of the trigger during the 1997 data-taking period is discussed.