40MHz scouting at the CMS experiment

Experiments at the Large Hadron Collider rely on sophisticated trigger systems to select and store a small fraction of "interesting" collision events. These systems are crucial for managing the enormous data rates produced by the experiments, ensuring that their physics program can be effectively carried out. However, events that are not selected are lost forever, which may limit the discovery potential by discarding signals that fall outside the trigger criteria and budget. This thesis presents the development and first implementation of a 40MHz Level-1 trigger scouting system for the CMS experiment at the Large Hadron Collider. Designed to capture and process data flowing through the L1 trigger boards at the bunch crossing rate before any trigger selection, this system enables the exploration of uncharted regions of phase space by bypassing traditional trigger constraints. A complete demonstrator was successfully deployed and operated during the 2024 LHC pp run. Early data from this demonstrator has been utilized in the initial steps toward a low-mass dijet search, an analysis typically constrained by stringent trigger thresholds due to the overwhelming background from QCD multi-jet production. In addition, this work explores new triggerless data acquisition and processing techniques, implemented within the CMS Drift Tubes muon detector Phase-2 demonstrator. This allowed the collection of valuable data for detector monitoring and background studies during pp collisions. Furthermore, a novel data acquisition system based on Remote Direct Memory Access technology was developed, offering an efficient data transfer mechanism with the potential to enhance both triggerless systems and standard data acquisition methods.