Performance of heavy-flavour jet identification in the CMS high-level trigger in proton-proton collisions at $\sqrt{s}$ = 13.6 TeV

Abstract

The CMS trigger system plays a crucial role during data taking, reducing the large collision rate delivered by the LHC to a few kHz for data storage and subsequent offline analysis. The system aims to maintain a high selection efficiency for a wide range of processes, including those involving jets originating from heavy-flavour quarks (b and c), which provide a distinctive signature in many physics analyses. To achieve this while maintaining a sustainable trigger output rate, dedicated jet flavour identification methods are developed and optimized for use in the high-level trigger (HLT). This paper presents the design, commissioning, and performance of deep-learning-based jet identification algorithms deployed in the HLT during 2022$-$2024, for proton-proton collisions at $\sqrt{s}$ = 13.6 TeV. The new algorithms enabled significant improvements in signal efficiency for a variety of key physics processes, including the non-resonant production of Higgs boson pairs decaying to four b quarks, as well as Higgs boson production via both vector boson fusion and in association with a $\mathrm{t\bar{t}}$ pair, in the H $\to$ $\mathrm{b\bar{b}}$ and H $\to$ $\mathrm{c\bar{c}}$ decay channels.