Ponente
Pierfrancesco Butti
Descripción
ATLAS is a multipurpose experiment at the LHC proton-proton collider. In order to reconstruct trajectories of charged particles, ATLAS is equipped with a tracking system built using different technologies, silicon planar sensors (pixel and micro-strip) and gaseous drift-tubes, all embedded in a 2T solenoidal magnetic field. For the LHC Run II, the system is being upgraded with the installation of a new pixel layer, the Insertable B-layer (IBL).
ATLAS physics goals require high resolution, unbiased measurement of all charged particle kinematic parameters in order to assure accurate invariant mass reconstruction and interaction and decay vertex finding. These critically depend on the systematic effects related to the alignment of the tracking system.
In order to eliminate malicious systematic deformations, various advanced tools and techniques have been put in place. These include information from known mass resonances, energy of electrons and positrons measured by the electromagnetic calorimeters, beam-spot and primary vertex constrains, etc. Alignment algorithms are complemented by the extended online and offline monitoring scheme.
Despite being stable under normal running conditions, ATLAS tracking system responses to sudden environmental changes (temperature, magnetic field) by small collective deformations. These have to be identified and corrected in order to assure uniform, highest quality tracking performance throughout the whole data taking. Such a time-aware alignment
scheme was put in place for 2012 running.
An outline of the track based alignment approach and its implementation within the ATLAS software will be presented. Special attention will be paid to integration of the IBL to the alignment framework, techniques allowing to identify and eliminate tracking systematics as well as strategies to deal with time-dependent alignment. Performance from LHC proton-proton collision Run I and prospects for LHC Run II will be discussed.
Autor primario
Collaboration ATLAS
(CERN)
