2,454 research outputs found

    Performance of a First-Level Muon Trigger with High Momentum Resolution Based on the ATLAS MDT Chambers for HL-LHC

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    Highly selective first-level triggers are essential to exploit the full physics potential of the ATLAS experiment at High-Luminosity LHC (HL-LHC). The concept for a new muon trigger stage using the precision monitored drift tube (MDT) chambers to significantly improve the selectivity of the first-level muon trigger is presented. It is based on fast track reconstruction in all three layers of the existing MDT chambers, made possible by an extension of the first-level trigger latency to six microseconds and a new MDT read-out electronics required for the higher overall trigger rates at the HL-LHC. Data from pppp-collisions at s=8 TeV\sqrt{s} = 8\,\mathrm{TeV} is used to study the minimal muon transverse momentum resolution that can be obtained using the MDT precision chambers, and to estimate the resolution and efficiency of the MDT-based trigger. A resolution of better than 4.1%4.1\% is found in all sectors under study. With this resolution, a first-level trigger with a threshold of 18 GeV18\,\mathrm{GeV} becomes fully efficient for muons with a transverse momentum above 24 GeV24\,\mathrm{GeV} in the barrel, and above 20 GeV20\,\mathrm{GeV} in the end-cap region.Comment: 6 pages, 11 figures; conference proceedings for IEEE NSS & MIC conference, San Diego, 201

    Precision Drift Chambers for the Atlas Muon Spectrometer

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    ATLAS is a detector under construction to explore the physics at the Large Hadron Collider at CERN. It has a muon spectrometer with an excellent momentum resolution of 3-10%, provided by three layers of precision monitored-drift-tube chambers in a toroidal magnetic field. A single drift tube measures a track point with a mean resolution close to 100 micron, even at the expected high neutron and gamma background rates. The tubes are positioned within the chamber with an accuracy of 20 microns, achieved by elaborate construction and assembly monitoring procedures.Comment: 3 pages, 2 eps figures, Proceedings for poster at Physics in Collisions Conference (PIC03), Zeuthen, Germany, June 2003. FRAP1

    Development of Muon Drift-Tube Detectors for High-Luminosity Upgrades of the Large Hadron Collider

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    The muon detectors of the experiments at the Large Hadron Collider (LHC) have to cope with unprecedentedly high neutron and gamma ray background rates. In the forward regions of the muon spectrometer of the ATLAS detector, for instance, counting rates of 1.7 kHz/square cm are reached at the LHC design luminosity. For high-luminosity upgrades of the LHC, up to 10 times higher background rates are expected which require replacement of the muon chambers in the critical detector regions. Tests at the CERN Gamma Irradiation Facility showed that drift-tube detectors with 15 mm diameter aluminum tubes operated with Ar:CO2 (93:7) gas at 3 bar and a maximum drift time of about 200 ns provide efficient and high-resolution muon tracking up to the highest expected rates. For 15 mm tube diameter, space charge effects deteriorating the spatial resolution at high rates are strongly suppressed. The sense wires have to be positioned in the chamber with an accuracy of better than 50 ?micons in order to achieve the desired spatial resolution of a chamber of 50 ?microns up to the highest rates. We report about the design, construction and test of prototype detectors which fulfill these requirements

    Large-Scale Production of Monitored Drift Tube Chambers for the ATLAS Muon Spectrometer

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    Precision drift tube chambers with a sense wire positioning accuracy of better than 20 microns are under construction for the ATLAS muon spectrometer. 70% of the 88 large chambers for the outermost layer of the central part of the spectrometer have been assembled. Measurements during chamber construction of the positions of the sense wires and of the sensors for the optical alignment monitoring system demonstrate that the requirements for the mechanical precision of the chambers are fulfilled

    Commissioning of the Charged Lepton Identification with Cosmic Rays in ATLAS

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    The ATLAS detector is designed for the study of highly energetic proton proton collisions at the LHC and offers excellent charged lepton identification. Millions of cosmic rays recorded by the ATLAS detector in fall 2008 and summer 2009 were used to commission the charged lepton identification algorithms. Fake tau candidates allowed the verification of the distribution of tau identification variables predicted by Monte-Carlo simulations. Electrons produced by highly energy muons during the passage through the detector material were successfully identified by expoiting the transition radiation capability of the inner detector. The huge statistics of muon tracks allowed the alignment of the inner detector and muon spectrometer guaranteeing excellent muon momentum resolution and efficiency at the start of the LHC

    A novel approach to track finding in a drift tube chamber

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    A novel track finding approach for drift tube detectors

    Performance of the ATLAS Muon Drift-Tube Chambers at High Background Rates and in Magnetic Fields

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    The ATLAS muon spectrometer uses drift-tube chambers for precision tracking. The performance of these chambers in the presence of magnetic field and high radiation fluxes is studied in this article using test-beam data recorded in the Gamma Irradiation Facility at CERN. The measurements are compared to detailed predictions provided by the Garfield drift-chamber simulation programme

    Pion Correlations and Resonance Effects in ppbar Annihilation to 4pi0 at Rest

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    We study pi0pi0 correlations in the exclusive reaction ppbar -> 4pi0 at rest with complete reconstruction of the kinematics for each event. The inclusive distribution shows a dip at small invariant mass of the pion pair while a small enhancement in the double differential distribution is observed for small invariant masses of both pion pairs. Dynamical models with resonances in the final state are shown to be consistent with the data while the stochastic HBT mechanism is not supported by the present findings.Comment: 17 pages, 12 figure

    Construction and Test of MDT Chambers for the ATLAS Muon Spectrometer

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    The Monitored Drift Tube (MDT) chambers for the muon spectrometer of the AT- LAS detector at the Large Hadron Collider (LHC) consist of 3-4 layers of pressurized drift tubes on either side of a space frame carrying an optical monitoring system to correct for deformations. The full-scale prototype of a large MDT chamber has been constructed with methods suitable for large-scale production. X-ray measurements at CERN showed a positioning accuracy of the sense wires in the chamber of better than the required 20 ?microns (rms). The performance of the chamber was studied in a muon beam at CERN. Chamber production for ATLAS now has started
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