An FPGA based track finder for the L1 trigger of the CMS experiment at the High Luminosity LHC

Abstract

A new tracking detector is under development for use by the CMS experiment at the
\nHigh-Luminosity LHC (HL-LHC). A crucial requirement of this upgrade is to provide the ability
\nto reconstruct all charged particle tracks with transverse momentum above 2–3 GeV within 4 s so
\nthey can be used in the Level-1 trigger decision. A concept for an FPGA-based track finder using
\na fully time-multiplexed architecture is presented, where track candidates are reconstructed using a
\nprojective binning algorithm based on the Hough Transform, followed by a combinatorial Kalman
\nFilter. Ahardware demonstrator usingMP7processing boards has been assembled to prove the entire
\nsystem functionality, from the output of the tracker readout boards to the reconstruction of tracks with
\nfitted helix parameters. It successfully operates on one eighth of the tracker solid angle acceptance
\nat a time, processing events taken at 40 MHz, each with up to an average of 200 superimposed
\nproton-proton interactions, whilst satisfying the latency requirement. The demonstrated trackreconstruction
\nsystem, the chosen architecture, the achievements to date and future options for such
\na system will be discussed.