First-level Trigger Research Articles

A fast track trigger processor for the OPAL experiment at LEP, CERN

The authors present the operational features and an engineering overview of criteria used in designing and building the fast track trigger processor for the OPAL experiment. The function of the processor is to examine, between successive LEP beam crossings (22 mu m), the multihit data generated by two central drift chambers and to provide the OPAL first-level trigger with information about the topology and the multiplicity of good tracks. The classes of events looked for are in the form of straight tracks in the R-Z plane which originate in the interaction region. The tracks are found in the R-Z and the R- phi planes by 24 fast track-finder circuits operating in parallel using a novel histogramming technique. A semicustom coincidence array circuit is used to match tracks. >