Abstract

During the data taking period from 2009 until 2012, the ATLAS trigger has been very successfully used to collect proton-proton data at LHC centre-of-mass energies between 900 Ge V and 8 Te V at record breaking luminosities. The three level trigger system reduces the event rate from the design collisions per bunch crossing of up to 40 MHz to an average recording rate of about 300 Hz. Using custom electronics with input from the calorimeter and muon detectors, the first level rejects most background collisions in less than 2.5 μs. Then follow two levels of software based triggers. The trigger system is designed to select events by identifying muons, electrons, γ, τ, jets, and B hadron candidates, as well as using global event signatures, such as missing transverse energy. The high trigger efficiencies illustrate that we have achieved a very good level of understanding of both the detector and trigger performance and successfully selected suitable streamed data samples for analysis.

Highlights

  • ● Minor issues due to gas leaks in RPC and one run in 2011 with an issue of the jet algorithm after a hardware recovery

  • ● Trigger Signatures at the High Level Trigger: identifying physics objects corresponding to fundamental particles

  • ● Retuned selection for high pileup conditions ● More advance HLT selection algorithms ● Trigger thresholds only raised minimally w.r.t. 2011

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Summary

Data Taking Efficiency of Trigger System

● Trigger Signatures at L1: concerning the hardware components and the central trigger reprocessor (CTP). ● Trigger Signatures at the High Level Trigger: identifying physics objects corresponding to fundamental particles. ● Minor issues due to gas leaks in RPC and one run in 2011 with an issue of the jet algorithm after a hardware recovery

Evolution of the luminosity
Consequences on the Streaming
Calorimeter based Trigger Items
Trigger Rates for Missing Energy
Tau Trigger
Physics with the ATLAS trigger
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