ATLAS Qualification Task – Detector Alignment

ATLAS Qualification Task – Detector Alignment

As part of my qualification task within the ATLAS Collaboration, I worked on the performance study of the detector alignment algorithm for the High-Luminosity LHC (HL-LHC) upgrade, focusing on the new ATLAS Inner Tracker (ITk) geometry.

The HL-LHC will operate at unprecedented luminosities, requiring a complete replacement of the current inner detector due to radiation damage, bandwidth limitations, and tracking performance constraints. Precise alignment of the ITk is essential, as tracking accuracy is ultimately limited by how well the positions and orientations of individual detector modules are known over time.

My work focused on the migration and validation of the misalignment framework in Athena, the ATLAS software environment, using the latest ITk geometry. This framework is a critical component for testing and benchmarking the alignment algorithm, which minimizes global track residuals by optimizing six degrees of freedom (three translations and three rotations) for each detector element.

I implemented and validated several classes of misalignments, including global distortions used to verify detector groupings and geometry consistency, as well as more realistic, complex misalignments that emulate mechanical deformations and temperature-dependent effects observed in real detectors. The validation was performed by correlating applied analytical distortions with observed module displacements in simulation.

This work contributes to ensuring that the ATLAS alignment strategy remains robust and scalable for the HL-LHC era, where precise tracking must be maintained under extreme pile-up and long-term operational conditions. The results of this study were presented at the Japan Physical Society Spring Meeting 2023.

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