The Level-1 Track Finder for the CMS High-Luminosity LHC Upgrade

The upgrade of the Large Hadron Collider (LHC) to the High-Luminosity LHC (HL-LHC) will provide an increased instantaneous luminosity, yielding more data for physics analysis, but imposing greater demands on the triggering systems of the detectors. In response, the CMS Collaboration is designing a novel Level-1 (L1) hardware track trigger using data from the Outer Tracker. This paper describes an overview of the L1 track finder which runs a pattern recognition algorithm on programmable chips (FPGAs). It aims to reconstruct trajectories of all charged particles with a transverse momentum ($p_\text{T}$) greater than 2 GeV within 4 $\mu$s. L1 track reconstruction using tracker data is a novel technique at CMS and has been made possible thanks to the innovative design of the new Outer Tracker. The Outer Tracker sensor modules transmit only the hits compatible with particles of $p_\text{T}>2$ GeV to the off-detector track-finder electronics, which in turn sends the reconstructed tracks to the L1 trigger. The track-finding algorithm has been implemented in firmware, and smaller tests of the firmware have successfully been performed in both simulations and hardware. The current state of the L1 track finder will be discussed.