Performance of the CMS GE1/1 system at LHC Run-3 and prospects of the future ME0 system

Abstract We report on the operational performance and reliability of GE1/1, a new muon tracking and triggering station made of Triple-GEM detectors installed in the most forward region of the CMS muon spectrometer as part of the Phase-2 upgrades for LHC Run-3. The GE1/1 station, comprising 144 Triple-GEM detectors, has been collecting data since 2022. We detail its front-end electronics architecture, including VFAT3, GBTx, and VTRx components, and discuss issues encountered with VTRx transceiver outgassing and the mitigation strategies implemented. By optimizing the front-end electronics, we achieved significant improvements in time resolution, reaching 12 ns, and stabilized detector performance with 94% detection efficiency. Additionally, we provide insights into the planned ME0 station, focusing on the design advancements that will improve background rejection and timing capabilities in the forward region. These results contribute to the ongoing efforts to enhance the CMS muon detection and triggering system as the LHC luminosity increases.