Hardware-based Tracking at Trigger Level for ATLAS: The Fast TracKer (FTK) Project

TL;DR

The Fast TracKer (FTK) project provides a hardware-based track reconstruction system at the trigger level for the ATLAS detector, enabling efficient tracking in high-pileup conditions at the LHC.

Contribution

This paper introduces the FTK system, a novel hardware-based trigger-level tracking solution using associative memory and custom chips for pattern matching in ATLAS.

Findings

FTK achieves high-speed pattern matching for track candidates.

FTK integrates seamlessly with the ATLAS trigger system.

Expected performance improves trigger efficiency under high pile-up.

Abstract

Physics collisions at 13 TeV are expected at the LHC with an average of 40-50 proton-proton collisions per bunch crossing under nominal conditions. Tracking at trigger level is an essential tool to control the rate in high-pileup conditions while maintaining a good efficiency for relevant physics processes. The Fast TracKer is an integral part of the trigger upgrade for the ATLAS detector. For every event passing the Level-1 trigger (at a maximum rate of 100 kHz) the FTK receives data from all the channels of the silicon detectors, providing tracking information to the High Level Trigger in order to ensure a selection robust against pile-up. The FTK performs a hardware-based track reconstruction, using associative memory that is based on the use of a custom chip, designed to perform pattern matching at very high speed. It finds track candidates at low resolution (roads) that seed a full-resolution track fitting done by FPGAs. An overview of the FTK system with focus on the pattern matching procedure will be presented. Furthermore, the expected performance and the integration of FTK within the ATLAS trigger system will be discussed.