The performance of the New Small Wheel of the ATLAS detector in the heart of LHC Run-3

During the second long shutdown of the Large Hadron Collider (LHC) at CERN, the most important upgrade within the ATLAS experiment was the replacement of the two inner endcap stations of the Muon Spectrometer (MS), with the New Small Wheel (NSW). Consisting of two novel detector technologies, the small-strip Thin Gap Chambers (sTGC) and the resistive strips Micromegas (MM), the NSW is targeting the rejection of fake muons at the endcap region between pseudorapidity 1 . 3 < | η | < 2 . 4 . Furthermore, thanks to the excellent muon tracking and the improved triggering capability NSW contributes to the identification of muons coming from the interaction point with high precision. Following an extensive effort to finalise the commissioning of the new detectors, both technologies were integrated successfully into the ATLAS data acquisition, reconstruction and simulation, and in 2024 they were also fully integrated into the ATLAS trigger, offering a significant reduction of the ATLAS Level-1 trigger rate and further reducing the readout dead-time. Despite the demanding challenges and increased luminosity delivered by LHC, the ATLAS NSW completed important milestones and now demonstrates its readiness towards the end of the Run-3 data-taking period of LHC. These proceedings will present an overview of the advances made within 2024, followed by a brief report of the NSW performance in terms of tracking and triggering, using data recorded from proton–proton collisions at 13.6 TeV .