A. Salamon

Test beam results and integration of the ATLAS level-1 muon barrel trigger

The ATLAS level-1 muon trigger will be crucial for the online selection of events with high transverse momentum muons and for its correct association to the bunch-crossing corresponding to the detected events. This system uses dedicated coarse granularity and fast detectors capable of providing measurements in two orthogonal projections. The resistive plate chambers (RPCs) are used in the barrel region (|/spl eta/| < 1). The associated trigger electronics is based on a custom chip, the coincidence matrix, that performs space coincidences within programmable roads and time gates. The system is highly redundant and communicates with the ATLAS level-1 trigger processor with the MUCTPI interface. The trigger electronics provides also the readout of the RPCs. Preliminary results achieved with a full trigger tower with production detectors in the H8 test beam at CERN will be shown, in particular preliminary results on the integration of the barrel muon trigger electronics with the MUCTPI interface and with the ATLAS DAQ system will be discussed.

The RPC LVL1 trigger system of the muon spectrometer of the ATLAS experiment at LHC

The Atlas Trigger System has been designed to reduce the LHC interaction rate of about 1 GHz to the foreseen storage rate of about 100 Hz. Three trigger levels are applied in order to fulfill such a requirement. A detailed simulation of the ATLAS experiment including the hardware components and the logic of the Level-1 Muon trigger in the barrel of the muon spectrometer has been performed. This simulation has been used not only to evaluate the performances of the system but also to optimize the trigger logic design. In the barrel of the muon spectrometer the trigger will be given by means of resistive plate chambers (RPCs) working in avalanche mode. Before being mounted on the experiment, accurate quality tests with cosmic rays are carried out on each RPC chamber using the test station facility of the INFN and University laboratory of Napoli. All working parameters are measured and the uniformity of the efficiency on the whole RPC surface is required. A summary of the Napoli cosmic rays tests, together with a brief description of the Atlas Trigger, in particular of the Level-1 Muon Trigger in the barrel, and the results of the trigger simulation will be given.

The RPC Level-1 muon trigger of the ATLAS experiment at the LHC

The three-level ATLAS trigger system has been designed to reduce the initial LHC interactions rate from 1 GHz, to ~100 Hz in order to allow permanent data storage. This result must be achieved preserving the less probable physics signals against a large background therefore providing a challenge task for the trigger and DAQ system. The level-1 muon trigger in the barrel region of the muon spectrometer is provided by resistive plate chambers (RPC) working in avalanche mode. More than 1000 RPC units of different sizes will he installed covering a surface of about 3650 m2 with a 350000 readout channels. A detailed simulation of the level-1 has been developed in order to optimize the trigger logic design and to study its performances. A description of the level-1 trigger in the barrel and preliminary results of its performances are presented.

The ATLAS LVL1 Barrel Muon Trigger Commissioning with Cosmic Rays

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.

PERFORMANCES OF THE ATLAS LEVEL-1 MUON TRIGGER PROCESSOR IN THE BARREL

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 pT 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.

The ATLAS level-1 barrel muon trigger performances

The level-1 muon trigger of ATLAS is expected to select events with high transverse momentum muons and associate them the correct bunch-crossing. For these purposes, dedicated fast detectors provide coarse measurement of the muon transverse momentum and high efficiency in its discrimination, giving also tracking measurements in two orthogonal views. In the barrel region (|eta|<1) it makes use of resistive plate chambers (RPCs) as active detectors. The trigger and readout chain is based on custom ASIC chips, which perform both the time and spatial coincidence with programmable roads and signal time shaping, and the readout, with a time resolution of 1/8 of a bunch crossing. A calibration procedure will allow to align signals in time and improve the background rejection of the system. The trigger system performances have been studied, testing multiple trigger configurations, on a cosmics test-stand using a full trigger tower of the ATLAS muon barrel spectrometer and the complete ATLAS trigger chain

Test beam results from the ATLAS LVL1 muon barrel trigger and RPC readout slice

The ATLAS barrel level-1 muon trigger system has the following main requirements: coarse measurement and discrimination of the muon transverse momentum PT; bunch crossing identification; fast and coarse tracking to identify tracks in the precision chambers that are related to the muon candidate; 2nd-coordinate measurement with a required resolution of 5-10 mm. Integration tests have been carried out between the various components of the system and in conjuction with the detector, front-end and other general sub-systems of the experiment. Results from test beam measurements have been performed in the CERN H8 test beam area, where production detectors from one full trigger tower have been installed.

Study of the performances of the level-1 trigger system for muons in the barrel of ATLAS with cosmic rays

The muon trigger in ATLAS is crucial for all the main physics channels to be studied at the design center of mass energy and luminosity of LHC and also for the initial phase of data taking with beams for the calibration of all the detectors. The level-1 trigger system for muons in ATLAS is performed using dedicated RPC chambers in the |η| ≪ 1 region. The trigger electronics provides both trigger and readout information. This system is being commissioned using cosmic rays with the full trigger and data acquisition chains. Monitoring tools have been developed in order to spot problems during data taking and determine the quality of the data and the trigger performance. Moreover, using the data taken during the commissioning phase, with partial availability of the detector, some studies have been performed to allow the optimization of the trigger system, based on different choises of the configuration parameters, also as a function of the detector working point. In this paper we would like to describe the extensive tests performed on the system and illustrate the possible performances with different conditions.

The ATLAS RPC Test Stand at INFN Roma Tor Vergata

The ATLAS experiment at the LHC uses plastic laminates RPCs as first level trigger detectors in the barrel up to pseudorapidity |eta| < 1. A set of quality controls are performed on the RPC chambers before they are sent to CERN for integration and installation on the experiment. Three test stands were installed for this purpose in INFN Divisions of Lecce, Napoli and Roma Tor Vergata. The results of the BOL-type chambers tested in Rome are presented.

Corrigendum to The ATLAS RPC detector control system: Problems, solutions and new opportunities [Nucl. Instr. and Methods in Physics Research, A 602/3(2009) 796-800]

Corrigendum to ‘‘The ATLAS RPC detector control system: Problems, solutions and new opportunities’’ [Nucl. Instr. and Methods in Physics Research, A 602/3(2009) 796–800] G. Aielli a,c, , P. Camarri , R. Cardarelli , A. Di Ciaccio , L. Di Stante , B. Liberti , F. Marchese , E. Pastori , A. Polini , A. Salamon , R. Santonico c,b a E.N.E.A. Frascati, Via Enrico Fermi 45, 00044 Frascati (RM), Italy b Physics Department, University of Rome ‘‘Tor Vergata’’, Via della Ricerca Scientifica 1, 00195 Roma, Italy c I.N.F.N. Sec. of Roma ‘‘Tor Vergata’’, Via della Ricerca Scientifica 1, 00195 Roma, Italy d I.N.F.N. Sec. of Bologna, Via Irnerio 46, 40126 Bologna, Italy