Pattern recognition in the HADES spectrometer: an application of FPGA technology in nuclear and particle physics

HADES is a second-generation dilepton spectrometer for hadron and heavy ion physics at the SIS Accelerator facility of GSI Darmstadt, Germany. The physics programme requires the detection of rare events in an environment of several GBytes/s of background data. This paper describes the dedicated trigger system which works together with a pipelined data acquisition system to suppress background events by 2 orders of magnitude. The trigger system is based on pattern recognition algorithms implemented in FPGAs and DSPs.