Speaker
Alex Christopher Martyniuk
(University College London)
Description
This contribution describes the trigger selection configuration system
of the ATLAS low- and high-level trigger (HLT) and the upgrades it
received in preparation for LHC Run 2.
The ATLAS trigger configuration system is responsible for applying the
physics selection parameters for the online data taking at both
trigger levels and the proper connection of the trigger lines across
those levels. Here the low-level trigger consists of the already
existing central trigger (CT) and the new Level-1 Topological trigger
(L1Topo), which has been added for Run 2. In detail the tasks of the
configuration system during the online data taking are
* Application of the selection criteria, e.g. energy cuts, minimum
multiplicities, trigger object correlation, at the three trigger
components L1Topo, CT, and HLT
* On-the-fly, e.g. rate-dependent, generation and application of
prescale factors to the CT and HLT to adjust the trigger rates to
the data taking conditions, such as falling luminosity or rate
spikes in the detector readout
* Recording of the complete trigger configuration for any given point
in time, for later use by data analysts
The core of the trigger configuration system is an oracle database
(TriggerDB), with a dedicated schema to reflect the L1Topo, CT, and
HLT configuration needs. A java-based UI serves as the front-end to
the TriggerDB for the trigger experts to store new and modify existing
trigger configurations. C++-based database reader software exists for
the trigger clients to retrieve configurations from the database. Web
interfaces exist to display the information to a large group of ATLAS
members.
With the vast amount of upgrades of the CT and HLT during the last two
years, and the addition of the L1Topo, substantial changes to the
database and software were necessary, which will be presented.
Technical problems, such as the low-latency distribution of the
configuration across the HLT computing farm and the synchronous
application to the data will be addressed. Also the propagation of
the trigger configuration database from the data-taking side to
various ATLAS data reconstruction sites will be discussed, including a
short description how the same trigger configuration mechanism is
being used for ATLAS Monte Carlo simulation. New features such an
automated luminosity tracking and prescale application system, which
optimizes the ATLAS data taking efficiency, will also be shown.
Primary author
Alex Christopher Martyniuk
(University College London)
Co-authors
Carlos Chavez
(University of Liverpool)
Joerg Stelzer
(CERN)
Mark Stockton
(McGill University (CA))
Michele Faucci Giannelli
(Royal Holloway, University of London)
Werner Wiedenmann
(University of Wisconsin (US))
Mr
William Panduro Vazquez
(Imperial College London)
