[Show abstract][Hide abstract] ABSTRACT: The ATLAS muon spectrometer, currently in the installation phase, uses dedicated detectors to be able to trigger on high transverse momentum muons in the range 6-20 GeV/c resistive plate chambers (RPC) are equipping the barrel region in the middle and outer station, while precision chambers (monitored drift tubes, MDT) are present also in the inner layer. The RPCs have the required timing and spatial resolution of about 2 ns times 1 cm, to be able to associate the muon to the correct bunch crossing and provide the second coordinate measurements to the MDTs. In order to successfully commission the chambers, cosmic runs are taken to check and validate the readout and trigger chain, and cosmic rates are measured and compared against values obtained with a cosmic ray Monte Carlo generator and full detector simulation. The first part of the detector under commission is the set of horizontal chambers positioned between the feet of the detector. The first results obtained in the ATLAS cavern will be presented. The first cosmic data taking collects signals from chambers arranged in six trigger towers, covering about one quarter of the full detector length. The experience gained on this small part of the detector will be very useful to define the commissioning work for the whole detector.
[Show abstract][Hide abstract] ABSTRACT: The ATLAS first level trigger is designed to reduce the LHC interaction rate from 1 GHz to 75–100 kHz. The first level muon trigger in the barrel is described together with test beam results and current commissioning and integration status at CERN.
[Show abstract][Hide abstract] ABSTRACT: The ATLAS level-1 muon trigger will select events with high transverse momentum and tag them to the correct machine bunch-crossing number with high efficiency. Three stations of dedicated fast detectors provide a coarse p T measurement, with tracking capability on bending and non-bending projections. In the Barrel region, hits from doublets of Resistive Plate Chambers are processed by custom ASIC, the Coincidence Matrices, which performs almost all the functionalities required by the trigger algorithm and the readout. In this paper we present the performance of the level-1 trigger system studied on a cosmic test stand at CERN, concerning studies on expected trigger rates and efficiencies.
[Show abstract][Hide abstract] ABSTRACT: Due to the huge interaction rates and the tough experimental environment of pp collisions at a centre-of-mass energy sqrt(s)=14 TeV and luminosities of up to 10^34cm^-2s^-1, one of the experimental challenges at the LHC is the triggering of interesting events. In the ATLAS experiment a three-level trigger system is foreseen for this purpose. The first-level trigger is implemented in custom hardware and has been designed to reduce the data rate from the initial bunch-crossing rate of 40MHz to around 75 kHz. Its event selection is based on information from the calorimeters and dedicated muon detectors. This article gives an overview over the full first-level trigger system including the Calorimeter Trigger, the Muon Trigger and the Central Trigger Processor. In addition, recent results are reported that have been obtained from test-beam studies performed at CERN where the full first-level trigger chain was established successfully for the first time and used to trigger the read-out of up to nine ATLAS sub-detector systems.