Speaker
Mogens Dam
(Niels Bohr Institute)
Description
The ATLAS tau trigger is a challenging component of the online event
selection, as it has to apply a rejection of 10^6 in a very short time
with a typical signal efficiency of 80%. Whilst in the first hardware
level narrow calorimeter jets are selected, in the second and
third software levels candidates are refined on base of simple but
fast (second level) and slow but accurate (third level) algorithms.
In these two levels, the data from various subdetectors are analysed,
however the overall data volume transported through the system (both
input subdetector data and output trigger output) has to be minimised.
The requirements of the tau trigger together with measured performance
during ATLAS cosmics run will be presented.
Triggering on tau leptons is a particularly challenging task, as
the signature characteristics are not much different from the
overwhelming QCD background. Advanced multi-variate optimisation
techniques help to find cut based criteria, which are suitable for
usage at trigger level. However, the procedure will be repeated on
data. First steps in this direction done in the commissioning of the first
and second levels are discussed as well as preparations for fast
commissioning with first LHC data.
Author
Alan Watson
(University of Birmingham)
