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Status of ATLAS experiment A.Myagkov IHEP,Protvino On behalf of the ATLAS collaboration LHC p-p collisions at √s=14TeV 2 1 Ldes 10 cm s 34 bunch crossing every 25 ns (40 MHz) Large Hadron Collider Lake of Geneva CMS LHCb ALICE ATLAS Temperature of superconducting magnet 1.9 K (2.3 for CMBR) Assuming the machine can be operated for 200 days per year and assuming the luminosity lifetime of 15 hours maximum total integrated luminosity per year of ~ 100 fbˉ¹ Physics at the LHC s at corresponds to conditions around here • 25m diameter Basic numbers: • 46m total length • 7000t weight •~ 3000 km of cables • installed just across the CERN main site, 92 meters below ground • ATLAS cavern: 55m long, 32m wide, 35m high: just large enough for the detector – ‘ship in a bottle’, but have to assemble in situ Main surface building SX1 Control room ATLAS has over 2000 scientists and engineers from 37 countries and 167 institutions, 550 MCHF. First beam event in ATLAS 10th of September First beam event in ATLAS 10th of September Detector components … 4 super-conducting magnets: solenoid + 3 toroids Silicon Pixel detector Solenoid field 2T in inner detector region toroid field peak strength 4T 80 M channels, intrinsic TileCal hadronic calorimeter resolution 10 x 110 μm Sandwich Silicon tracker structure: iron absorber + ~ 6 ∙106 channels scintillator tiles 80 μm wide strips ~ 10000 channels Transition Radiation Tracker Muon spectrometer Xe field straw tubes, ~1200 precision chambers electron – pion separation LAr calorimeters (EMC, HC) for track reconstruction ~ 160000 + 10000 channels ~600 RPC and ~3600 ~ 35 hits/track for track (EMC,HC) TGC trigger chambers reconstruction 10%/√E energy resolution for e,γ Stand-alone momentum Trigger for electrons, photons and re-solution Δpt/pt < 10% jets up to 1 TeV Base characteristics • Tracking (||<2.5, B=2T) : -- Si pixels and strips -- Transition Radiation Detector (e/ separation) • Calorimetry (||<5) : -- EM : Pb-LAr -- HAD: Fe/scintillator (central), Cu/W-LAr (fwd) • Muon Spectrometer (||<2.7) : air-core toroids with muon chambers Installation – the years 2003 to 2007 … 2007 • All material lowered thru 2 shafts, Ø 12 and 18m Jun 2007 • Heaviest piece of equipment: 280 t • ‘Ballet’ of logistics at the ATLAS site 2006 Dec 2004 Dec2005 Aug.2003 Current understanding of the performance of ATLAS detector is based on the analysis of : Full simulation of the different processes Test beam data Calibration runs in each subsystem Cosmic runs SCT: 4 cylindrical double layers (one axial Inner detector and one with a stereo angle of 40 mrad) of barrel silicon-microstrip sensors layers with Pixels : 3 layers with R=30,37,44, 51 cm 6 M channels R=5, 8 and 12 cm intrinsic resolution 10 x 110 μm 80 M channels TRT: 4 mm straw tubes, arranged in 2∙160 disks and 73 layers, 40 K channels •Double purpose: Enhanced pion-electron separation (TR γ’s convert into e’s in Xe) , track reconstruction/momentum determination (average 35 hits/track, single tub res. 130 μm)) TRT/SCT installed Aug 2006 Pixel installed June 2007 /pT ~ 5x10-4 pT 0.01 Cosmic event in TRT, 23 August 08. Rejection of light jets and cjets versus b-jet efficiency for t tbar events. . Current status: Pixels: 3 leaky cooling loops in End Cap (12 modules per loop). tested only a few days in April 2008,interrupted by cooling plant incident. SCT: Defective channels – 1.2 % (0.7 % in 2009) TRT:Switch to Xenon based mixture of Xe/CO2/O2 (Xe provides Transition Radiation features = particle identification) around September 15. Dead channels 1.2-2.0%, delivery of some readout elements being completed run with Xenon or not – to be decided LAr and Tile Calorimeters Tile barrel Tile extended barrel LAr hadronic end-cap (HEC) LAr EM end-cap (EMEC) LAr EM barrel LAr forward calorimeter (FCAL) LAr calorimeters Uses accordion-shaped electrodes and lead (in barrel) absorbers Electromagnetic Calorimeter barrel,endcap: Pb-Lar ~10%/√E energy resolution e/γ Hadron Calorimeter barrel Iron-Tile EC/Fwd Cu/W- LAr (~20000 channels) /E ~ 50%/E 0.03 pion (10 ) Since May 2008 full calorimeter up, integrated in DAQ, slow control Expected performance and current status Overall reconstruction and identification efficiency of various levels of electron cuts: loose, medium, and tight isol. as a function of ET for single electrons (open symbols) and for isolated electrons in a sample of physics events with a busy environment Current status: 729 of 173312 channels dead (0.4%): no physics/calibration pulses , dominated by failing optical links • 0.3% channels with calibration problems, corrections implemented Hadronic Tile calorimeter scintillating tiles + iron absorbers, ΔE/E = 50%/√E 3% Installation in the cavern Ext. Barrel C December 2004 Barrel October 2005 Ext. Barrel A May 2006 Current status From M8 Over about 5k cells, 10k channels: 43 masked cells (two drawers) 20 cells have one masked channel (information can be recovered using the other channel) Status on 12-Sep: Tile Cal was the first Three drawers do not send data subsystem in cosmic runs One drawer is unstable (need to cycle power from time to time) Two drawers send some %% of corrupted events Total number of affected cells is ~100 - 2% (but not in all events) We are within the 5% of failures needed for expected Missing ET reconstruction performances. Muon Spectrometer -- Barrel Muon barrel has ~ 650 individual stations, arranged in 3 concentric circles. Dual purpose: track reconstruction (resolution 50μm/station → Δpt/pt < 10% up to 1 TeV) and (level-1) trigger Barrel stations consist of a Monitored Drift Chamber (MDT), built from 3 cm drift tubes, and equipped with a optical monitoring system to reconstruct chamber deformations Resistive Plate Chambers (RPC) in the middle and outer layer, operated in proportional mode for triggering MDT -RPC Correlation (cosmics data) Muon Spectrometer -- Endcap ~600 MDT and 64 CSC (Cathode Strip Chambers) precision chambers for tracking 1578 Thin Gap Chambers (TGCs) as trigger: multi-wire proportional chambers, wire spacing 1.8 mm, operated with n-pentane/CO2 mixture Geometry: 2 Small (movable), 2x4 Big (movable) and 2 Outer Wheels, interconnected by optical alignment system Forward muon spectrometer - ‘Big Wheels’ are all installed Current status MDT – All Services Connected (1 ½ chambers out) ◦ EE chambers installed later TGC – Fully Installed (0.3% dead) RPC – Fully Installed (very few dead channels) CSC – hardware installed ◦ ROD firmware – being worked on Alignment System 99% operational ◦ A few blocked optical lines Trigger and Data Acquisition The ATLAS Trigger and Data Acquisition is based on a three-level hierarchy designed to reduce the data rate from 10’s PetaBytes/sec produced by ATLAS to ~100 MegaBytes/sec of interesting physics Level 1 decision based on data from calorimeters and muon trigger chambers; synchronous at 40 MHz Level 2 uses Regions of Interest identified by Level-1 (< 10% of full event) with full granularity from all detectors Event Filter has access to full event and can perform more refined event reconstruction Event data flow from online to offline We are going to collect raw data Ballon (30 km) at 320 MB/s for 50k seconds/day CD stacks with and ~100 days/year 1 year LHC data (~ RAW dataset: 1.6 PB/year 20 km ) Processing these events will require ~10k CPUs full time Concord (15 km) At least 10k CPUs are also needed for continuous simulation production of at Mt.Blanc 4.8 km least 20-30% of the real data rate and for analysis There is no way to concentrate all needed computing power and storage capacity at CERN.The LEP model will not scale to this 50 CD-ROM -> 36 GB -> 6 cm level The ATLAS Distributed Computing hierarchy (GRID) : 1 Tier-0 centre: CERN 10 Tier-1 centres: BNL(Brookhaven, US), NIKHEF/SARA (Amsterdam,NL), CC-IN2P3 (Lyon, FR), FZK (Karlsruhe, DE), RAL (Chilton, UK), PIC (Barcelona, ES),CNAF (Bologna, IT), NDGF(DK/SE/NO), TRIUMF (Vancouver, CA), ASGC (Taipei, TW) ~35 Tier-2 facilities, some of them geographically distributed, in most participating countries ◦ Tier-3 facilities in all participating institutions Commissioning “Online” 1. Commissioning of individual subsystems in pit (almost finished) 2. Integration of subsystems into ATLAS trigger and DAQ system (on-going) Several global commissioning runs using cosmic rays in 2008: ◦ - operate the whole experiment ◦ - achieve stable running for long periods ◦ - exercise Trigger and DAQ ◦ (data flow, run control, configuration) ◦ - operate control room as if data taking Should not forget “Offline” - Full Dress Rehearsal (FDR): a “stress test” of the full data processing and analysis chain from point-1 to the end user Looking ahead: Commissioning with beam Cosmic triggers ◦ Exercise whole system, HLT, read out, TTC system, ◦ Alignment data, coarse timing, synchronisation, ◦ Monitoring, exercise reconstruction/ Tier 0 efficient for barrel Single beam triggers (beam-gas, beam halo muons) ◦ End-cap detector timing & response ◦ High energy showers for more precise pulse shape Then collisions ! ◦ Understanding of full detector, high statistics ◦ Increasing precision In-situ calibrations Initial Ultimate Samples e/γ E scale ~ 2% 0.1 % Z-> ee, J/ψ e/γ uniformity 1-2 % 0.5 % Z-> ee Jet E scale 5-10 % ~ 1% W->jj in tt,W/Z +jets Tracking alignment 10-50 µm < 10 µm tracks, Z->µµ Muon alignment 100-200 µm 30 µm inclusive µ, Z->µµ Overall uniformity of energy response of EM calorimeter as a function of the number of events or as a function of the luminosity. Preparing to the physics (CSC notes) The most important at the first time topics were selected and studied Now the analysis is finished In total: ~80 notes, ~ 2.000 pages TDR + archive: Collect the notes into a CSC book and submit them to the hep- archive, CONCLUSION The LHC Physics Program has breakthrough discovery potential ATLAS is ready for data taking We are really excited with the physics starting soon!
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