Overview of Trigger in CMS experiment

• Bunch crossing rate : 40MHz
• proton Collision rate : 10^9 Hz
• it is not easy to handle all events at once, so "Triggering" is very neccessary for valued analysis.
• Generally, can separate two parts - L1 trigger and High Level Trigger(HLT)
• L1 trigger will be done in the online with Muon system detectors.
• After L1, we can reduce the rate into 100kHz.
• Triggering goal is to decrease their rate upto 100Hz as long as possible

Muon Triggering

* Pt cut requirement (depending on HLT menu, but this is general case following TDR)

• single muon : > 5 GeV?/c
• double muon : > 3 GeV?/c

- L2 trigger : StandAlone? Muon

• Seeded by Level-1 muon
• Refitting muon track with Kalman filtering technique only in muon chambers (DT/CSC/RPC track segments)
• Trajectory works from inside out, Fitting works from outside in

- L3 trigger : Including inner tracker hits

• Track reconstruction and matching with track in muon chamber and inner track (pixel seeds, and propagate from innermost layers out including muon)
• Vertex finder method : divisive, histogramming method

-- DongHoMoon - 20 Aug 2009