Performance requirements of proposed ATLAS second level trigger architectures from simple models

To cope with the expected event rates and data volumes of the LHC and the ATLAS detector, the ATLAS second level trigger will require significantly higher communication bandwidths and processing power than existing HEP experiments. The LVL2 trigger uses full precision data from the detectors to examine regions of interest (RoI) identified by the LVL1 trigger. Features are first extracted from individual sub-detectors, then combined into a trigger object from each RoI. The event is accepted if the pattern of objects is found in a menu of trigger requirements, based on the ATLAS physics requirements. ATLAS is a general purpose detector which will study physics processes including Higgs and SUSY particle searches and CP violation in B-decays. For low luminosity running the trigger will make a full unguided search of tracking detectors to look for signatures of interesting B-decays.