CMS Level-1 Trigger

The CMS Level-1 Trigger system is described with an emphasis on algorithms useful for b-physics studies. A special algorithm is designed for electrons from b-quark decays which takes advantage of the fine granularity crystal electromagnetic calorimeter. With a luminosity of 1033 cm−2s−1, one can achieve 10 GeV and 5 GeV thresholds for single and double electron triggers, respectively. The muon trigger combines fast dedicated detectors (RPC) with precise muon chambers (drift tubes and cathode strip chambers). They provide a sharp pt cut which can be set at ∼8–10 GeV for a single muon trigger. The two-muon trigger pt cut is limited only by the energy loss in absorber and is equal to ∼4 GeV in the barrel and ∼2 GeV in the endcaps.