Track-based alignment of the CMS muon detector

The outermost layer of the CMS experiment measures muon tracks with over 700 independent tracking chambers, mounted on modular wheels and disks. These supports can shift and flex under the magnetic force of the CMS solenoid, so the positions and orientations of the chambers must be determined under operating conditions. Two methods will be used to identify the chambers' true locations: a survey system built into the detector and a software-based optimization of tracks. We will discuss the latter, which poses interesting challenges due to the large amount of material between muon chambers. Proper alignment of the muon system is one of the most significant factors in muon momentum resolution above 1 TeV.