A fast hardware tracker for the ATLAS trigger system (original) (raw)
Selecting interesting events online is a very challenging task in LHC experiments. By the end of 2014, the LHC will run with an energy of 13 or 14 TeV and instantaneous luminosities which could exceed 10 34 interactions per cm 2 and per second. The triggering in the ATLAS detector is realized using a three level trigger approach, in which the first level is hardware based and the second and third stage are realized using large computing farms. It is a crucial and non-trivial task for triggering to maintain a high efficiency for events of interest while suppressing effectively the very high rates of inclusive QCD processes, which constitute mainly background. At the same time the trigger system has to be robust and provide sufficient operational margins to adapt to changes in the running environment. In the current design track reconstruction can be performed only in limited regions of interest at second stage trigger and the CPU requirements may limit this even further at the highest instantaneous luminosities. Providing high quality track reconstruction over the entire detector volume for the second stage trigger decision would allow gains in efficiency and background rejection for triggers on tau leptons, b-hadrons and help reduce the luminosity dependence of isolation requirements for electrons and muons. The Fast Track Trigger (FTK) is an ongoing upgrade project aimed at providing track reconstruction using the silicon microstrip and pixel detectors. Pattern recognition and track fitting are executed in a hardware system utilizing massive parallel processing and achieve a tracking performance close to that of the global track reconstruction. The FTK systems design, based on a mixture of advanced technologies and expected physics performance will be presented.
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Hadron collider triggers with high-quality tracking at very high event rates
IEEE Transactions on Nuclear Science, 2004
We propose precise and fast-track reconstruction at hadron collider experiments, for use in online trigger decisions. We describe the features of fast-track (FTK), a highly parallel processor dedicated to the efficient execution of a fast-tracking algorithm. The hardware-dedicated structure optimizes speed and size; these parameters are evaluated for the ATLAS experiment. We discuss some applications of high-quality tracks available to the trigger logic at an early stage, by using the LHC environment as a benchmark. The most interesting application is online selection of b-quarks down to very low transverse momentum, providing interesting hadronic samples: examples are , potentially useful for jet calibration, and multi-b final states for supersymmetric Higgs searches. The paper is generated from outside the ATLAS experiment and has not been discussed by the ATLAS collaboration.
Hadron collider triggers with offline-quality tracking at very high event rates
13th IEEE-NPSS Real Time Conference, 2003
We propose precise and fast-track reconstruction at hadron collider experiments, for use in online trigger decisions. We describe the features of fast-track (FTK), a highly parallel processor dedicated to the efficient execution of a fast-tracking algorithm. The hardware-dedicated structure optimizes speed and size; these parameters are evaluated for the ATLAS experiment. We discuss some applications of high-quality tracks available to the trigger logic at an early stage, by using the LHC environment as a benchmark. The most interesting application is online selection of b-quarks down to very low transverse momentum, providing interesting hadronic samples: examples are , potentially useful for jet calibration, and multi-b final states for supersymmetric Higgs searches. The paper is generated from outside the ATLAS experiment and has not been discussed by the ATLAS collaboration.
Enhancement of the ATLAS trigger system with a hardware Tracker finder FTK
Journal of Instrumentation, 2010
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 design luminosity of 10 34 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.
FTK: A Fast Track Trigger for ATLAS
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We describe the design and expected performance of a the Fast Tracker Trigger (FTK) system for the ATLAS detector at the Large Hadron Collider. The FTK is a highly parallel hardware system designed to operate at the Level 1 trigger output rate. It is designed to provide global tracks reconstructed in the inner detector with resolution comparable to the full offline reconstruction as input of the Level 2 trigger processing. The hardware system is based on associative memories for pattern recognition and fast FPGAs for track reconstruction. The FTK is expected to dramatically improve the performance of track based isolation and b-tagging with little to no dependencies of pile-up interactions.
As the LHC luminosity is ramped up to 3× × × ×10 34 cm −2 s −1 and beyond, the high rates, multiplicities, and energies of particles seen by the detectors will pose a unique challenge. Only a tiny fraction of the produced collisions can be stored on tape and immense real-time data reduction is needed. An effective trigger system must maintain high trigger efficiencies for the physics we are most interested in, and at the same time suppress the enormous QCD backgrounds. This requires massive computing power to minimize the online execution time of complex algorithms. A multi-level trigger is an effective solution for an otherwise impossible problem. The Fast Tracker (FTK) is a proposed upgrade to the current ATLAS trigger system that
Proceedings of Topical Workshop on Electronics for Particle Physics — PoS(TWEPP-17), 2018
The ATLAS Fast TracKer (FTK) was designed to provide full tracking for the ATLAS high-level trigger by using pattern recognition based on Associative Memory (AM) chips and fitting in high-speed field programmable gate arrays. The tracks found by the FTK are based on inputs from all modules of the pixel and silicon microstrip trackers. The as-built FTK system and components are described, as is the online software used to control them while running in the ATLAS data acquisition system. Also described is the simulation of the FTK hardware and the optimization of the AM pattern banks. An optimization for long-lived particles with large impact parameter values is included. A test of the FTK system with the data playback facility that allowed the FTK to be commissioned during the shutdown between Run 2 and Run 3 of the LHC is reported. The resulting tracks from part of the FTK system covering a limited-region of the detector are compared with the output from the FTK simulation. It is shown that FTK performance is in good agreement with the simulation.
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