Alignment Strategy for the Tracking Stations of FASER

The ForwArd Search ExpeRiment (FASER), located 480 m downstream from the ATLAS beam interaction point, is designed to study light weakly-interacting long-lived particles (LLPs) and neutrino interactions. One of the main components of FASER, used to detect the decay products of LLPs, is the four tracking stations, each with three layers and 24 semiconductor tracker (SCT) modules. Particles leave electronic hit signals on SCT modules, and tracks reconstructed from hits are used for analysis. To exploit the excellent intrinsic resolution of the silicon microstrip detectors, high-accuracy alignment is required. A local χ2 alignment algorithm is designed and tested on both Monte-Carlo and collision data to perform software alignment on the tracking stations. By aligning the FASER tracking stations, the performance of track reconstruction from detector hits is substantially improved. Additionally, the software alignment shows promising results when compared to survey data.