FTK: A hardware real-time track finder for the ATLAS trigger system

This paper presents an overview of the ATLAS Fast TracKer (FTK) processor, reporting the design of the system, its expected performance, and the current integration status. The FTK is an upgrade of the trigger system of the ATLAS experiment. The system is designed to reduce the event rate from the proton-proton collisions occurring at 40 MHz to about 1 kHz for the expected LHC luminosity (2 × 10^34 cm-^2s^-1). To achieve this selection rate, the FTK system must exploit an intensive use of particle tracking. To this purpose, a dedicated hardware tracker has been designed: the FTK processor. To achieve the required performance, FTK uses a combination of custom VLSI chips and latest generation FPGAs, all embedded in dedicated boards, and it exploits a fully parallel architecture. FTK provides track reconstruction based on the full silicon (inner) detector with resolution comparable to the offline reconstruction with a latency of approximately 100 μs.