The Muon System of the Run II DØ Detector

Abstract We describe the design, construction, and performance of the upgraded DO muonsystem for Run II of the Fermilab Tevatroncollider. Significant improvements have been made to the major subsystems of the DO muondetector: trigger scintillation counters, tracking detectors, and electronics. The Run II central muondetector has a new scintillation countersystem inside the iron toroidand an improved scintillation countersystem outside the iron toroid. In the forward region, new scintillation counterand tracking systems have been installed. Extensive shielding has been added in the forward region. A large fraction of the muonsystem electronics is also new.