CERN Accelerating science

Internal Note
Report number	CMS-DN-2023-022 ; CERN-CMS-DN-2023-022
Title	A Novel Timing Trigger with the CMS Hadron Calorimeter
Author(s)	Kopp, Gillian Baron (Princeton U.) ; Tully, Christopher (Princeton U.) ; Kennedy, Kiley Elizabeth (Princeton U.) ; Chung, Wonyong Paul (Princeton U.) ; Hoienko, Svitlana (Princeton U.) ; Mans, Jeremiah Michael (Minnesota U.) ; Krohn, Michael David (Minnesota U.) ; Crossman, Bryan James (Minnesota U.) ; Hiltbrand, Joshua (Baylor U.) ; Skuja, Andris (Maryland U.) ; Wang, Long (Maryland U.)
Publication	2023
Imprint	31 Oct 2023
Number of pages	34
Subject category	Detectors and Experimental Techniques
Accelerator/Facility, Experiment	CERN LHC ; CMS
Abstract	A low-level hardware timing trigger using the Hadron Calorimeter (HCAL) in the Compact Muon Solenoid (CMS) experiment at CERN is designed and deployed for Run 3 of the Large Hadron Collider (LHC), with data taking beginning in 2022. The new Level-1 trigger relies on the Phase 1 upgrade of the HCAL, which provides greater segmentation granularity and an increased number of readout channels, and enables timing information to be used in the hardware trigger system. The timing trigger is designed to increase the CMS experiment's sensitivity to long-lived particles (LLPs) by introducing a trigger that processes data at 40 MHz to identify jets arriving at delayed times. In addition to identifying events with jets arriving with a time delay, the trigger also identifies events with unique depth signatures, both of which are characteristics of LLPs. This trigger is the first of its kind, in that timing and segmentation information is used at the hardware level to identify LLP candidate events. This paper reviews the algorithm, implementation, and performance of the trigger, and includes a discussion of the HCAL timing capabilities and online time alignment.