Level-1 Tracking at CMS for the HL-LHC

The success of the CMS physics program at the HL-LHC requires maintaining sufficiently low trigger thresholds to select physics processes. With an average expected 200 pileup interactions, it is critical to achieve this while maintaining manageable trigger rates by including tracking information in the Level-1 (L1) trigger. A 40 MHz silicon-based track trigger on the scale of the CMS central tracking system has never been built and can enable entirely new physics studies. The main challenges of reconstructing tracks in the L1 trigger are the large data throughput at 40 MHz and the need for a trigger decision within 12.5 𝜇s. To address these challenges, the CMS Outer Tracker for the HL-LHC uses modules with closely spaced silicon sensors to read out only hits compatible with charged particles above 2 GeV. This proceeding discusses the L1 tracking algorithm and its implementation, presents simulation studies of its estimated performance, and highlights results from hardware studies conducted at the CERN Tracker Integration Facility.