Fast TracKer: A fast hardware track trigger for the ATLAS detector

Abstract The trigger system at the ATLAS experiment is designed to lower the event rate occurring from the nominal bunch crossing rate of 40 MHz to about 1 kHz for a LHC luminosity of the order of 10 34 cm − 2 s − 1 . To achieve high background rejection while maintaining good efficiency for interesting physics signals, sophisticated algorithms are needed which require an extensive use of tracking information. The Fast TracKer (FTK) trigger system, part of the ATLAS trigger upgrade program, is a highly parallel hardware device designed to perform track-finding at 100 kHz. Modern, powerful Field Programmable Gate Arrays (FPGAs) form an important part of the system architecture, and the combinatorial problem of pattern recognition is solved by 8000 standard-cell ASICs used to implement an Associative Memory architecture. The availability of the tracking and subsequent vertex information within a short latency ensures robust selections and allows improved trigger performance for the most difficult signatures, such as b -jets and τ leptons.