Upgrade of the ATLAS Level-0 TGC Endcap Muon Trigger for HL-LHC

Abstract

The Level-0 endcap muon trigger system for the ATLAS experiment at the HL-LHC, which performs a fast muon reconstruction using the Thin Gap Chamber (TGC), is being developed to cope with more than three times higher luminosity environment and achieve a better performance. The efficiency in the high-p T region was found to be 9% higher than the current system. The TGC hit signals digitized at the frontend electronics are sent to the backend, and muon candidates are reconstructed using the hits. Then, the candidates are combined with information from other detectors to refine transverse momentum (p T) reconstruction and reduce fake trigger candidates. The precise online estimation of p T allows us to apply highly efficient trigger condition to select events that contains muons with high p T.The Sector Logic (SL) is responsible for the online fast reconstruction in the L0 Muon Trigger system, and the algorithms are implemented in a large-scale modern FPGA on the SL. Each step of the reconstruction algorithms is first implemented as individual modules, and all trigger algorithms run sequentially as a chain in a combined firmware. The trigger algorithms are being tested on the prototype trigger board, the SL. The resource usage of the FPGA is reasonable and the trigger latency is within the acceptable limit.