Search

The Atlas Muon Spectrometer is designed to reach a very high transverse momentum resolution for muons in a pT range extending from 6 GeV/c up to 1 Tev/c. The most demanding design goal is an overall uncertainty of 50 microns on the sagitta of a muon with pT = 1 TeV/c. Such precision requires an accurate control of the positions of the muon detectors and of their movements during the experiment operation. Moreover, the light structure of the Muon Spectrometer, consisting mainly of drift tubes assembled in three layers of stations, imply sizable distortions of the nominal layout of individual chambers, due to mechanical stress and thermal gradients. Corrections for mis-alignments and deformations, which will be provided run-time by an optical alignment system, must be integrated in the software chain leading to track reconstruction and momentum measurement. Here we discuss the implementation of run-time dependent corrections for alignment and distortions in the detector description of the Muon Spectrometer along with the strategies for studying such effects in dedicated simulations. Some preliminary results obtained in the context of the ATLAS Condition Data Challenge effort are also presented.

The Muon Digitization is the simulation of the Raw Data Objects (RDO), or the electronic output, of the Muon Spectrometer. It has been recently completely re-written to run within the Athena framework and to interface with the Geant4 Muon Spectrometer detector simulation. The digitization process consists of two steps: in the first step, the output of the detector simulation, henceforth referred to as Muon Hits, is converted to muon digits, i.e., intermediate objects that can be fed into the reconstruction. In the second step, the muon digits are converted into RDO, the transient representation of raw the data byte stream. We will describe the detailed implementation of the first step of the muon digitization, where the detector simulation output is "digitized" into muon digits. We will describe the fundamentals of the Muon Digitization algorithms, outlining the global structure of the Muon Digitization, with some emphasis on the simulation of piled-up events. We will also describe the details of the digitization validation against the Monte Carlo information.

The size and complexity of LHC experiments raise unprecedented challenges not only in terms of detector design, construction and operation, but also in terms of software models and data persistency. One of the more challenging tasks is the calibration of the 375000 Monitored Drift Tubes, that will be used as precision tracking detectors in the Muon Spectrometer of the ATLAS experiment. An accurate knowledge of the space-time relation is needed to reach the design average resolution of 80 microns. The MDT calibration software has been designed to extract the space-time relation from the data themselves, through the so-called auto-calibration procedure, to store and retrieve the relevant information from the conditions database, and to properly apply it to calibrate the hits to be used by the reconstruction algorithms, taking into account corrections for known effects like temperature and magnetic field. We review the design of the MDT calibration software for ATLAS and present performance results obtained with detailed GEANT4-based simulation and real data from the recent combined test beam. We discuss the implementation of the conditions database for MDT calibration data in the framework proposed by the LHC Computing Grid (LCG). Finally, we present early results from detector commissioning with cosmic ray events and plans for the ATLAS Computing System Commissioning test in 2006.