[en] The detector description database, the event data structure, the condition database are all examples (among others) of complex collections of objects which need to be unambiguously identified, not only internally to their own management structure, but also from one collection to the other. The requirements for such an identification scheme include the management of identifiers individually attached to each collected object, the possibility to formally specify these identifiers (eg through dictionaries), to generate optimised and compact representations for these identifiers, and to be able to use them as sorting and searching keys. The authors present here the generic toolkit developed in the context of the Atlas experiment to primarily provide the identification of the readout elements of the detector. This toolkit offers several either generic or specialized component such as: an XML based dictionary with which the formal specification of a particular object collection is expressed, a set of various binary representations for identifier objects (offering various level of compaction), range operators meant to manipulate ranges of identifiers, and finally a collection manager similar to the STL map but optimised for an organization keyed by Identifiers. All these components easily interoperate. In particular the identifier dictionary offers means of specifying permitted cardinalities of objects at each level of the hierarchy. This can then be translated into Identifier Ranges, or can be used as the strategy driver for high compactification of the identifiers (e.g. to store very large number of identified objects). Current use of this toolkit within the detector description will be presented, and expected or possible other usages will be discussed

[en] ATLAS is one of the four experiments at the Large Hadron Collider (LHC) at CERN. This experiment has been designed to study a large range of physics including searches for previously unobserved phenomena such as the Higgs Boson and super-symmetry. The ATLAS Muon Spectrometer (MS) is optimized to measure final state muons in a large momentum range, from a few GeV up to TeV. Its momentum resolution varies from (2-3%) at 10-100 GeV/c to 11% at 1 TeV, taking into account the high level background environment, the inhomogeneous magnetic field, and the large size of the apparatus (24 m diameter by 44 m length). A robust muon identification and high momentum measurement accuracy is crucial to fully exploit the physics potential of the LHC. The basic principles of the muon reconstruction packages Muonboy, STACO, MuTag are discussed in this paper. Details of the modifications done in order to adapt the pattern recognition to the cosmic-ray configuration as well as its performance with the recent cosmic-rays and single beam data are presented.

[en] The study of the Z Boson and its decay into two muons at ATLAS provides several interesting aspects. Since the mass and the width of the Z-Boson is known to a very high precision from LEP experiments, Z decays can be used for precision tests of the detector, in particular for alignment issues. Various effects of misalignments in the ATLAS Muon Spectrometer on the reconstructed Z-Boson resonance are discussed. Moreover, the impacts on the precision of muon momentum reconstruction were studied

[en] Studies of catastrophic muon energy losses were performed during the combined run period in the CERN H8 Testbeam experimental area where approximately one octant of the ATLAS muon spectrometer was installed along with parts from the Inner Detector and the Electromagnetic and Hadronic calorimeters. Muon tracks reconstructed in the muon spectrometer were associated with the energy deposited in the electromagnetic Liquid Argon and the hadronic Tile calorimeters. On this basis, muons were separated from pions that contaminated the beam and muons with catastrophic energy losses were identified. The measured probability of muons to suffer such a loss was compared to results from Monte Carlo expectations

[en] While many high energy experiments use track fitting software that is based solely on the Kalman Filter technique, the ATLAS offline reconstruction also has several global track fitters available. One of these is the GlobalChi2Fitter, which is based on the scattering angle formulation of the track fit. One of the advantages of this method over the Kalman fit is that it can provide the scattering angles and related quantities (e.g. the residual derivatives) to the alignment algorithms. The algorithm has been implemented in the new common tracking framework in ATLAS, the philosophy of which is to improve the modularity and flexibility of the tracking software. This flexibility has proven crucial for the understanding of the data from the testbeam and cosmic runs. An overview of recent results will be presented, in particular the results from the combined tracking with the inner detector and the muon spectrometer using the cosmics data

[en] A robust muon identification and high momentum measurement accuracy is crucial to fully exploit the physics potential that will be accessible with the ATLAS experiment at the LHC at CERN. In this paper an overview of the muon reconstruction software is given and performance results from detailed Geant4-based simulations are presented

[en] The ATLAS detector is designed to exploit the full potential of the LHC, identifying and providing highly accurate energy and momentum measurements of particles emerging from the LHC proton-proton collisions. High-momentum final-state muons are among the most promising signatures at the LHC, thanks to a high-resolution Muon Spectrometer with standalone triggering and momentum measurement. The Muon Spectrometer is a large and complex system of gaseous detectors, requiring a detailed simulation to exploit its full capabilities. Over the last few years these systems have been described in terms of a set of geometrical primitives known as GeoModel. This description is now used in the GEANT4-based simulation program, which is fully operational and integrated into the ATLAS common analysis framework

[en] The implementation of run-time dependent corrections for alignment and distortions in the detector description of the ATLAS Muon Spectrometer is discussed, along with the strategies for studying such effects in dedicated simulations

[en] ATLAS detector is designed to exploit the full discovery potential of the LHC proton-proton collider at CERN, at an energy of 14 TeV. The detector, which is optimized for operating at high luminosity, features an inner tracker, Electromagnetic and Hadronic calorimeters and a Muon Spectrometer. The ATLAS Muon Spectrometer is composed of tracking and trigger detectors, which span a total area of 5500 m². The design of the spectrometer provides very good momentum resolution that varies between 2% and 10% for momentum ranging from 5 GeV to 1 TeV. To achieve this resolution, the 1200 individual tracking chambers composed of Monitored Drift Tubes (MDT) are constructed with mechanical precision better than 20 μm, while the position and deformation of individual chambers will be monitored with an optical alignment system to be better than 40 μm during data taking. In 2004, a combined systems test of a φ sector of the following ATLAS sub-detectors: the Inner Detector, the Liquid Argon Calorimeter, the Tile Hadronic Calorimeter and the Muon Spectrometer, was performed in the H8 beam line at the CERN SPS. Results obtained on the alignment of the MDT chambers in the Muon Spectrometer setup, the performance of the MDT chambers and the reconstruction of Muon tracks using the combined information from both the Inner Detector and the Muon Spectrometer are presented here

[en] The muon spectrometer of the LHC detector ATLAS provides an independent and precise muon track measurement using three layers of precision drift tube chambers in a toroidal magnetic field with a bending power ∫Bdl of 2Tm to 8Tm. Muon tracks are reconstructed with 97% efficiency and a momentum resolution about 3% for most of the range and better than 10% for transverse momenta up to 1 TeV/c. The latter requires the knowledge of the magnetic field with 1% accuracy and misalignment corrections of the track curvature with an accuracy of about 30μm. The magnetic field is measured by Hall probes on each chamber with sufficient precision. The misalignment corrections are given by a system of optical sensors. We present methods which allow us to measure the performance of the muon spectrometer during the operation of the ATLAS detector. The alignment of the chambers can be verified with single muon tracks by making use of redundant momentum measurements in the spectrometer. The muon reconstruction efficiency and the momentum resolution can be determined with muons from Z decays