Speaker
Manuel Dias-Gomez
(University of Geneva, Switzerland)
Description
The ATLAS experiment at the Large Hadron Collider (LHC) will face the challenge of
efficiently selecting interesting candidate events in pp collisions at 14 TeV center-
of-mass energy, whilst rejecting the enormous number of background events, stemming
from an interaction rate of about 10^9 Hz. The Level-1 trigger will reduce the
incoming rate to around O(100 kHz). Subsequently, the High-Level Triggers (HLT),
which are comprised of the second level trigger and the event filter, will need to
reduce this rate further by a factor of O(10^3). The HLT selection is software based
and will be implemented on commercial CPUs using a common framework, which is based
on the standard ATLAS object-oriented software architecture. In this talk an
overview of the current implementation of the selection for electrons and photons in
the trigger is given. The performance of this implementation has been evaluated
using Monte Carlo simulations in terms of the efficiency for the signal channels,
the rate expected for the selection, the data preparation times, and the algorithm
execution times. Besides the efficiency and rate estimates, some physics examples
will be discussed, showing that the triggers are well adapted for the physics
programme envisaged at LHC. The electron/gamma trigger software has been also
integrated in the ATLAS 2004 combined test-beam, to validate the chosen selection
architecture in a real on-line environment.
