The precise reconstruction of the trajectories of charged particles created in proton–proton collisions at CERN’s Large Hadron Collider (LHC) is a key ingredient in many of the physics processes studied by the ATLAS Collaboration. Almost every measurement performed using the ATLAS detector, from Standard Model processes to searches for new physics phenomena, relies on the accurate reconstruction of charged particles. ATLAS uses the Inner Detector (ID) tracking system to reconstruct the trajectories (tracks) of charged particles as they traverse the detector. The precision achieved for the track parameters is determined, among other factors, by the knowledge of the ID geometry, i.e. the location and orientation of the detector elements. The purpose of the detector alignment is to determine, as precisely as possible, the actual geometry of the active detector elements of the tracking system, and to follow changes in the geometry with time.
In this seminar, the methods developed and employed in ATLAS for the ID alignment during LHC's Run-2 and Run-3 will be presented, highlighting the major challenges that appeared during the detector operation, which include fast time-dependent displacements and deformations of various ID sub-detectors.
Elia Bertoldo, Clara Fernández, Giada Caneva