Speaker
Antonio Sidoti
(ROMA1)
Description
During the data taking period from 2009 until 2011, the ATLAS trigger has been
used very successfully to collect proton-proton data at LHC centre-of-mass energies
between 900 GeV and 7 TeV. The three-level trigger system reduces the event
rate from the design bunch-crossing rate of 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 ns. Then follow two levels of software-based triggers. The trigger system is
designed to select events by identifying muons, electrons, photons, taus,
jets, and B hadron candidates, as well as using global event signatures, such as
missing transverse energy.
We give an overview of the performance of the different trigger selections based
mainly on the experience during the 2011 LHC run. Distributions of selection
variables used by the different trigger selection are shown and compared with
the offline reconstruction. Examples of trigger efficiencies with respect
to offline reconstructed signals are presented and compared to simulation. These
results illustrate that we have achieved a very good level of understanding of
both the detector and trigger performance. Furthermore, we describe how the
trigger selections have evolved with increasing LHC luminosity to cope with the
increasing pileup conditions. If already available the initial experience from
the 2012 run will be presented.
for the collaboration
ATLAS collaboration
Primary author
Dr
Imma Riu
(IFAE Barcelona)
