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During 2006 and spring 2007, integration and commissioning of trigger and data acquisition (TDAQ) equipment in the ATLAS experimental area has progressed. Much of the work has focused on a final prototype setup consisting of around eighty computers representing a subset of the full TDAQ system. There have been a series of technical runs using this setup. Various tests have been run including those where around 6 k Level-1 preselected simulated proton-proton events have been processed in a loop mode through the trigger and dataflow chains. The system included the readout buffers containing the events, event building, second level and third level trigger processors. Aspects critical for the final system, such as event processing times, have been studied using different trigger algorithms as well as the different dataflow components.
The Liquid Argon calorimeters play a central role in the ATLAS (A Toroidal LHC Apparatus) experiment. The environment at the Large Hadron Collider (LHC) imposes strong constraints on the detectors readout systems. In order to achieve very high precision measurements, the detector signals are processed at various stages before reaching the Data Acquisition system (DAQ). Signals from the calorimeter cells are received by on-detector Front End Boards (FEB), which sample the incoming pulse every 25ns and digitize it at a trigger rate of up to 75~kHz. Off-detector Read Out Driver (ROD) boards further process the data and send reconstructed quantities to the DAQ while also monitoring the data quality. In this paper, the ATLAS Liquid Argon electronics chain is described first, followed by a detailed description of the off-detector readout sys...
During summer and fall 2004, the response of a full slice of the ATLAS barrel de, tector to different particles was studied in controlled beam. One module of the ATLAS , liquid argon barrel calorimeter – identical to the production modules and read out by the final front-end and back-end electronics – was used for electromagnetic calorimetry. This paper presents and discusses the electron performance of the LAr barrel calorime ter, including linearity, uniformity, and resolution with different amounts of material upstream the calorimeter and energies ranging from 1GeV to 250GeV.
The energy loss spectrum of 150 GeV muons has been measured with a prototype of the ATLAS hadron calorimeter in the H8 beam of the CERN SPS. The differential probability ${\rm {d}}P/{\rm {d}}v$ per radiation length of a fractional energy loss $v = \Delta E_{\mu} / E_{\mu}$ has been measured in the range $v$ = 0.01 $\div$ 0.95; it is compared with the theoretical predictions for energy losses due to bremsstrahlung and production of electron-positron pairs or of energetic knock-on electrons. The integrated probability $\int_{0.01}^{0.95} ({\rm {d}}P/{\rm {d}}v) {\rm {d}}v$ is $(1.610\pm0.015_{{\rm {stat}}}\pm0.105_{{\rm {syst}}})\cdot10^{-3}$ in agreement with the theoretical predictions $1.556\cdot10^{-3}$ and $1.619\cdot10^{-3}$. Agreement with theory is also found in two intervals of $v$ where production of electron-positron pairs and...
The ATLAS experiment is preparing for data taking at 14 TeV collision energy. A rich discovery physics program is being prepared in addition to the detailed study of Standard Model processes which will be produced in abundance. The ATLAS multi-level trigger system is designed to accept one event in 2 · 105 to enable the selection of rare and unusual physics events. The ATLAS calorimeter system is a precise instrument, which includes liquid Argon electro-magnetic and hadronic components as well as a scintillator-tile hadronic calorimeter. All these components are used in the various levels of the trigger system. A wide physics coverage is ensured by inclusively selecting events with candidate electrons, photons, taus, jets or those with large missing transverse energy. The commissioning of the trigger system is being performed with cosm...
A study of high energy muons traversing the ATLAS hadron Tile calorimeter in the barrel region in the energy range between 10 and 300~GeV is presented. Both test beam experimental data and Monte Carlo simulations are given and show good agreement. The Tile calorimeter capability of detecting isolated muons over the above energy range is demonstrated. A signal to background ratio of about 10 is expected for the nominal LHC luminosity ($10^{34} cm^{-2} sec^{-1}$). The photoelectron statistics effect in the muon shape response is shown. The e/mip ratio is found to be $ 0.81 \pm 0.03$; the e/$\mu$ ratio is in the range 0.91 - 0.97. The energy loss of a muon in the calorimeter, dominated by the energy lost in the absorber, can be correlated to the energy loss in the active material. This correlation allows one to correct on an event by even...
Prototypes of the FERMI system have been used to read out a prototype of the ATLAS hadron calorimeter in a beam test at the CERN SPS. The FERMI read-out system, using a compressor and a 40 MHz sampling ADC, is compared to a standard charge integrating read-out by measuring the energy resolution of the calorimeter separately with the two systems on the same events. Signal processing techniques have been designed to optimize the treatment of FERMI data. The resulting energy resolution is better than the one obtained with the standard read-out.
Prototypes of the FERMI system have been used to read out a prototype of the ATLAS hadron calorimeter in a beam test at the CERN SPS. The FERMI read-out system, using a compressor and a sampling ADC, is compared to a standard charge integrating read-out by measuring the energy resolution of the calorimeter separately with the two systems on the same events.
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