Reconstruction and trigger performance studies of the New Small Wheel of the ATLAS detector

The expected instantaneous luminosity increase for Run 3 and the high luminosity phase of LHC up to 7.5 $\times$ 10$^{34}$ fb$^{-1}$ requires upgrading the muon spectrometer of the ATLAS experiment. The New Small Wheel (NSW) consist of new generation gas detectors, Micromegas and small-strip Thin Gap Chambers, replacing the first measuring station in the forward region of the muon spectrometer. This contribution presents the muon trigger and reconstruction performance of the NSW. These performances are studied through Monte Carlo simulations with different detector configurations and background levels, and compared with data acquired with particle beams and cosmic muons.