Integration of the ACTS track reconstruction toolkit in the ATLAS software for HL-LHC operations

The High Luminosity LHC (HL-LHC) is set to begin in 2029 and will be Run 4 of the ATLAS detector. As part of the phase 2 upgrade, the ATLAS Inner tracking system will be replaced with an all-silicon Inner Tracker (ITk). The higher luminosity will cause an increase in pileup, $\mu$, the number of interactions per crossing, resulting in more tracks, increasing the computational complexity of track reconstruction. A Common Tracking Software (ACTS) is an experiment independent software toolkit that will be extensively used by ATLAS in Run 4 to handle this increased complexity. A full ACTS-based tracking chain has now been implemented for the ITk, and the performance of several algorithms within this chain has been studied. The results presented reflect the current performance, although many algorithms are still undergoing optimization, with future improvements anticipated.