Bonn 2010 – scientific programme

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T: Fachverband Teilchenphysik

T 55: Spurkammern I

T 55.3: Talk

Monday, March 15, 2010, 17:25–17:40, HG ÜR 3

Initial alignment of the ATLAS muon spectrometer with straight tracks — •Igor Potrap, Steffen Kaiser, Oliver Kortner, and Hubert Kroha — Max-Planck-Institut für Physik, Munich, Germany

The muon spectrometer of the ATLAS experiment at the Large Hadron Collider at CERN is designed to measure muon momenta of up to 1 TeV with a resolution of better than 10 %. It consists of three layers of precision drift tube chambers located in a toroidal field of superconducting air-core magnets. To achieve the desired momentum resolution with the 3-point track sagitta measurement, the muon chambers have to be aligned with an accuracy of better than 30 µm in the track bending plane. Muon chamber movements are monitored by an optical alignment system with a precision of few microns. Initial chamber positions have to be determined with straight muon tracks from cosmic rays and from proton-proton collisions in a dedicated run of the ATLAS detector with the toroid magnets switched off. A least-square algorithm which determines initial chamber positions in the spectrometer using straight muon tracks has been developed. It was tested with simulations and with cosmic data recorded during the commissioning period of the ATLAS experiment. The results show that the combination of track-based and optical alignment allows to reach the required level of accuracy.