Speaker
Mr
Anton Kapliy
(University of Chicago)
Description
As the LHC luminosity is ramped up to the design level of 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)[1], [2] is a proposed upgrade to the current ATLAS trigger system
that will operate at full Level-1 output rates and provide high quality tracks reconstructed
over the entire detector by the start of processing in Level-2. FTK solves the combinatorial
challenge inherent to tracking by exploiting massive parallelism of associative memories that
can compare inner detector hits to millions of pre-calculated patterns simultaneously. The
tracking problem within matched patterns is further simplified by using pre-computed linearized
fitting constants and leveraging fast DSP’s in modern commercial FPGA’s. Overall,
FTK is able to compute the helix parameters for all tracks in an event and apply quality
cuts in approximately one millisecond. By employing a pipelined architecture, FTK is able
to continuously operate at Level-1 rates without deadtime.
The system design is defined and studied with respect to high-Pt Level-2 objects: b-jets,
tau-jets, and isolated leptons. We test FTK algorithms using ATLAS full simulation with
WH events at the LHC design luminosity. The reconstruction quality is evaluated comparing
FTK results with the tracking capability of an offline tracking algorithm. Finally, we compare
several architectural choices to optimize the latency and hardware system size.
References
[1] A. Annovi et al. The fast tracker processor for hadronic collider triggers. IEEE Transactions
on Nuclear Science, 48:575–580, 2001.
[2] A. Annovi et al. Hadron collider triggers with high-quality tracking at very high event
rates. IEEE Transactions on Nuclear Science, 51:391–400, 2004.
Author
Mr
Anton Kapliy
(University of Chicago)
