Enhancement of the ATLAS trigger system with a hardware tracker finder FTK

The existing three-level ATLAS trigger system is deployed to reduce the event rate from the bunch crossing rate of 40 MHz to ∼200 Hz for permanent storage at the LHC luminosity of 1034 cm^−2 s^−1 . When the LHC exceeds the design luminosity, the load on the Level-2 trigger system will significantly increase due both to the need for more sophisticated algorithms to suppress background and the larger event sizes. The Fast Tracker is a proposed upgrade to the current ATLAS trigger system that will operate at the full Level-1 accepted rate of 100 kHz and provide high quality tracks at the beginning of processing in the Level-2 trigger, by performing track reconstruction in hardware with massive parallelism of associative memories. The concept design is being advanced and justified with the performance in important physics areas, b-tagging, τ-tagging and lepton isolation. The prototyping with current technology is underway and R&D with new technologies has been started.