Event data from proton-proton collisions at the LHC will be selected by the ATLAS experiment by a three level trigger system, which reduces the initial bunch crossing rate of 40 MHz at its first two ...trigger levels (LVL1+LVL2) to ~3 kHz. At this rate the Event-Builder collects the data from all Read-Out system PCs (ROSs) and provides fully assembled events to the the Event-Filter (EF), which is the third level trigger, to achieve a further rate reduction to ~200 Hz for permanent storage. The Event-Builder is based on a farm of 0 (100) PCs, interconnected via Gigabit Ethernet to 0 (150) ROSs. These PCs run Linux and multi-threaded software applications implemented in C++. All the ROSs and one third of the Event-Builder PCs are already installed and commissioned. Performance measurements have been exercised on this initial system, which show promising results that the required final data rates and bandwidth for the ATLAS event builder are in reach.
We have studied the ϕ→a0(980)γ process with the KLOE detector at the Frascati ϕ-factory DAΦNE by detecting the ϕ→ηπ0γ decays in the final states with η→γγ and η→π+π−π0. We have measured the branching ...ratios for both final states: Br(ϕ→ηπ0γ)=(7.01±0.10±0.20)×10−5 and (7.12±0.13±0.22)×10−5, respectively. We have also extracted the a0(980) mass and its couplings to ηπ0, K+K−, and to the ϕ meson from the fit of the ηπ0 invariant mass distributions using different phenomenological models.
The ϕ-meson leptonic widths, Γee and Γμμ, are obtained, respectively, from the e+e− forward–backward asymmetry and the μ+μ− cross section around the ϕ-mass energy. We find Γee=1.32±0.05±0.03 keV and ...ΓeeΓμμ=1.320±0.018±0.017 keV. These results, compatible with Γee=Γμμ, provide a precise test of lepton universality. Combining the two results gives Γℓℓ(ϕ)=1.320±0.023 keV.
A fully instrumented slice of the ATLAS central detector was exposed to test beams from the SPS (Super Proton Synchrotron) at CERN in 2004. In this paper, the response of the central calorimeters to ...pions with energies in the range between 3 and 9
GeV is presented. The linearity and the resolution of the combined calorimetry (electromagnetic and hadronic calorimeters) was measured and compared to the prediction of a detector simulation program using the toolkit Geant 4.
We have searched for the decay ϕ→K0K¯0γ, by detecting KS pairs plus a photon and with the KS-mesons decaying to π+π−, in a sample of about 1.5×109ϕ-decays collected by the KLOE experiment at DAΦNE. ...The reaction proceeds through the intermediate states f0(980)γ, a0(980)γ. We find five events with 3.2 events expected from background processes. We obtain the upper limit: BR(ϕ→K0K¯0γ)<1.9×10−8 at 90% CL.
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.
RPC cosmic ray tests in the ATLAS experiment Chiodini, G.; Aielli, G.; Aloisio, A. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
10/2007, Volume:
581, Issue:
1
Journal Article
Peer reviewed
Extensive tests with cosmic rays were performed with Resistive Plate Chamber (RPC) trigger chambers belonging to 6 muon stations of sector 13 installed in the ATLAS muon spectrometer. We illustrate ...the results of this pre-commissioning phase, which represents a test bench for the final commissioning of the ATLAS RPC system with cosmic rays.
In 2004, a combined system test was performed in the H8 beam line at the CERN SPS with a setup reproducing the geometry of sectors of the ATLAS Muon Spectrometer, formed by three stations of ...Monitored Drift Tubes (MDT). The full ATLAS analysis chain was used to obtain the results presented in this paper. The basic design performances of the Muon Spectrometer were verified. The stability of MDT calibration constants, the alignment system using optical devices and high energy tracks, as well as the intrinsic sagitta resolution of the Muon Spectrometer were studied and found to agree with expectations. The reconstruction of muon tracks using the combined information from both the Inner Detector and the Muon Spectrometer are also presented.
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