Dedicated triggers for displaced jets using timing information from electromagnetic calorimeter at HL-LHC

In this paper, we study the prospect of ECAL barrel timing to develop triggers dedicated to long-lived particles decaying to jets at the level-1 of HL-LHC. We construct over 20 timing-based variables, and identify two of them which have better performances and are robust against increasing PU. We estimate the QCD prompt jet background rates accurately using the stitching procedure for varying thresholds defining our triggers and compute the signal efficiencies for different LLP scenarios for a permissible background rate. The trigger efficiencies can go up to O(80%) for the most optimal trigger for pair-produced heavy LLPs having high decay lengths, which degrades with decreasing mass and decay length of the LLP. We also discuss the prospect of including the information of displaced L1 tracks to our triggers, which further improves the results, especially for LLPs characterised by lower decay lengths.

Automated summary

This paper studies the prospect of using ECAL barrel timing to develop triggers for long-lived particles decaying to jets at the level-1 of HL-LHC. The authors construct over 20 timing-based variables and identify two with better performances that are robust against increasing PU. Accurate estimation of QCD prompt jet background rates is achieved using the stitching procedure. The trigger efficiencies can reach up to O(80%) for heavy LLPs with high decay lengths, but decrease for lower masses and decay lengths. The authors also discuss the possibility of including information from displaced L1 tracks to further improve the results, especially for LLPs with lower decay lengths.