Design and Simulation of the First Level Global Muon Trigger for the CMS Experiment at CERN

The present thesis deals with the First Level Global Muon Trigger (GMT) for the Compact Muon Solenoid (CMS) Experiment at the Large Hadron Collider (LHC) of the European Particle Physics Laboratory CERN. The First Level Trigger electronics reduce the event rate from 40MHz (bunch crossing rate of the LHC) to 100 kHz, the maximal input rate of the higher level triggers, by selecting potentially interesting events on the basis of coarsely segmented data from the calorimeters and the three muon systems in CMS. It is the task of the GMT to combine independent measurements of regional triggers in each of the muon systems and to determine the best four muons in the entire detector for each bunch crossing. In order to apply isolation criteria and to achieve confirmation by the calorimeter the GMT further correlates muon measurements with regions in the calorimeter. The GMT algorithms were elaborated with the help of detailed simulations of the detector and trigger system. The logic design of the main GMT electronics board was developed based on the technology of Field Programmable Gate Arrays. In order to study di–muon trigger rates, a new method was devised to simulate triggers caused by the pile–up of an average of 17.3 inelastic interactions per bunch crossing at the LHC. By making use of the complementarity of the muon systems the GMT improves background rejection by a factor of five while increasing over–all efficiency. Duplicated measurements in the barrel/endcap overlap region are removed by cancel–out units. The total contribution of ghost triggers to the di–muon trigger rate can thereby be reduced to approximately 15 %. Trigger thresholds of 20 to 25 GeV/c in the single muon and 4 to 5 GeV/c in the di–muon trigger at the LHC design luminosity of $L = 10^{34} cm^{-2}s^{-1}$ are shown to be compatible with the required rate reduction resulting in excellent efficiency for most of the channels among the physics goals to be selected by muon triggers.