Speaker
Dr
Antonio Sidoti
(INFN Roma1 and University "La Sapienza")
Description
The ATLAS experiment at the LHC proton-proton collider at CERN will be faced with
several technological challenges. A three level trigger and data acquisition system
has been designed to reduce the 40 MHz bunch-crossing frequency, corresponding to an
interaction rate of 1GHz at the design instantaneous luminosity to about ~100 Hz
allowed by the permanent storage system. The capability to select events with muons
at an early stage of the trigger system is therefore crucial to cope with the
expected rates. In this paper we will describe the whole trigger and data aquisition
system of the muon system (Muon Trigger ``Vertical Slice''). The first level of
trigger (LVL1) is implemented on hardware, it selects high-pt muons with transverse
momentum above programmable thresholds with a coarse evaluation of the eta and phi
coordinate (the so called RoI, the "Region of Interest") using hits coming from the
trigger chambers of the Muon Spectrometer (MS), the rate is reduced to ~75-100 kHz.
The RoI are then passed to the second trigger lever (LVL2) implemented on an on-line
software architecture. The muFast algorithm reconstructs muons with transverse
momentum larger than ~6 GeV combining full granularity information inside RoIs from
trigger and precision chambers of the MS. Other algorithms will then combine outputs
coming from different ATLAS sub-detectors to further select muons with different
topologies. The rate is reduced to 1 kHz with a mean processing time of 10ms. A third
trigger level, the Event Filter (EF) will access the full event to reduce the rate.
Different algorithms will be implemented reconstructing events inside the MS and
combining the measurements of all ATLAS sub-detectors in order to provide the best
estimate of their momentum at the production vertex. Along with the algorithm
implementation and description we will also present the expected performances
relative to signal efficiencies, background rejection and execution time.
Author
Dr
Antonio Sidoti
(INFN Roma1 and University "La Sapienza")
