The first-level and high-level muon triggers of the Compact Muon Solenoid experiment at CERN

High transverse momentum muons are expected to play a crucial role in the discovery of the Standard Model Higgs, precision Standard Model measurements, as well as in the discovery of new physics such as Supersymmetry at CERN´s new Large Hadron Collider. In order to provide efficient and precise muon detection, three muon systems are utilized in the Compact Muon Solenoid (CMS) experiment: Drift Tubes in the barrel, Cathode Strip Chambers in the endcaps and Resistive Plate Chambers throughout for trigger information complementary to the high-precision tracking measurements of the first two systems. The CMS trigger has to reduce the event rate from the LHC bunch-crossing rate of 40 MHz to a rate of approximately 100 Hz, the maximum that can be recorded for offline analysis. This enormous reduction is achieved in several subsequent levels: while the first level trigger reduces the initial rate to a maximum of 100 kHz employing fully pipelined custom-built electronics, the following higher trigger levels will run on a high-performance farm of commercial processors allowing for full flexibility. Muon-trigger algorithms employed at the first and higher trigger levels are discussed. Special emphasis is given to the First-Level Global Muon Trigger, which increases efficiency and considerably improves rate reduction by optimally combining trigger information of all three muon systems. Detailed Monte-Carlo simulations of expected trigger rates and trigger efficiencies are presented.