A 40 MHZ PIPELINED TRIGGER FOR K-0-]2-PI(0) DECAYS FOR THE CERN NA48 EXPERIMENT

A first level trigger system based on a 40 MHz digital pipeline has be en developed for the CERN NA48 [1] experiment, aiming at measuring CP violation in K-0 --> 2 pi decays. The outputs of the 13340 cells of th e 10 m(3) liquid krypton calorimeter are summed into 64 X and 64 Y pro jection strips and continuously digitised with 40 MHz FADCs. This info rmation is used to reconstruct at each clock cycle and for the two cal orimeter projections, the number of clusters, the impact time of each of them (with a precision of about 3 ns), their total energy and the f irst and second moments of the energy distribution. Based on the quant ities listed above, a programmable look-up table system subsequently c omputes online the longitudinal position of the kaon decay vertex and performs an event selection. The system is described.