Upgrade of the Global Muon Trigger for the Compact Muon Solenoid experiment at CERN

The Large Hadron Collider is a large particle accelerator at the CERN research laboratory, designed to provide particle physics experiments with collisions at unprecedented centre-of-mass energies. For its second running period both the number of colliding particles and their collision energy were increased. To cope with these more challenging conditions and maintain the excellent performance seen during the first running period, the Level-1 trigger of the Compact Muon Solenoid experiment --- a sophisticated electronics system designed to filter events in real-time --- was upgraded. This upgrade consisted of the complete replacement of the trigger electronics and a full redesign of the system's architecture. While the calorimeter trigger path now follows a time-multiplexed processing model where the entire trigger data for a collision are received by a single processing board, the muon trigger path was split into regional track finding systems where each newly introduced track finder receives data from all three muon subdetectors for a certain geometric detector slice and reconstructs fully formed muon tracks from this. In contrast, the system in operation during the first data taking period was built around subdetector-specific track finders whose output tracks were merged in the Global Muon Trigger. This restructuring of the muon trigger required a novel system to receive muon objects from the track finding layer, remove any duplicate tracks, and forward the best-reconstructed objects to the global decision layer. The upgraded Global Muon Trigger (μGMT) was designed to satisfy the requirements for such a system. It receives muon track data from all regional track finder processors as well as energy information from the final stage of the calorimeter trigger. These muon tracks are ranked and sorted, while in parallel their azimuthal coordinate is corrected and duplicate muon tracks are removed. An isolation variable using the calorimetric information is computed before the eight highest-ranked muon tracks are sent to the upgraded Global Trigger (μGT) The μGT then determines whether a read-out process shall be initiated by applying complex algorithms on the muon tracks as well as on data received from the calorimeter trigger chain. This thesis presents the design and development of the μGMT, outlining the requirements as well as challenges encountered during development of the upgraded trigger. Furthermore, the excellent performance of the new system is demonstrated in the context of studies on quarkonia: Both the impact of the improved duplicate removal system as well as of the correction of the azimuthal coordinate are evaluated and shown to improve upon the performance demonstrated by the original Level-1 trigger. Additionally, a simple scheme that increases the purity of dedicated trigger algorithms to select J/ψ mesons by requiring the presence of two oppositely charged muons is presented and assessed.