Status of ATLAS and preparation for the Pb-Pb run QM 2009, Knoxville Jiří Dolejší Charles University Prague for the ATLAS collaboration

2 Performance & experience 2008 Single beam splash event on September 10th, 2008: particles from a beam hitting the collimator 140 m from ATLAS.

3 Performance & experience 2008 Muon detectors Calorimeters Inner detector

4 2008: Cosmic run from September 14th: Pixels: Efficiency of about 98.4% Optolinks tuned to 80Mbit/s SCT: 99% of SCT Barrel and 97% of SCT EndCaps were operated 99% of all modules operational 99.8% strips alive TRT: 97% of channels reading out ~99% of electronics working 2.9 M tracks collected in TRT Repairs, prospects for 2009: Cooling repairs & improvements Restart during May 09 SCT Pixels TRT

5 Inner detector – performance illustrations: Display of cosmic ray event going through the SCT and pixel detector (notice low noise) Alignment of upper and lower halves of cosmic tracks expressed in difference of d 0 – distance to vertex. Tracks are selected to have p T > 2 GeV. Tracks are required to have a hit in the Pixel B layer, 3 Pixel hits and in total 7 Silicon hits.

6 Calorimeters Liquid argon calorimeter: Successful operation in 2008: 97% power supplies OK 99.92% channels working Prospects for 2009: Power supplies repaired, monitoring improved Everything will be in place and ready to go by the end of April Tile calorimeter: Power supplies & controls: 99.2% OK 98.6% cells alive Calibration ready or being commissioned, cell equalization within a few %. Tasks for 2009: Further tuning of the 137 Cs cell inter- calibration, monitoring of PMT stability, data quality monitoring. Energy summed over 100 splash events in EM Presampler ATLAS Preliminary

Liquid argon calorimeter- illustration of performance: The 8-fold  structure induced by the toroid endcap is clearly visible at large radius (layers S1, S2, S3). The 16-fold structure is due to additional matter and shielding at low radius (Presampler PS). The sum of 100 splash events from Sept. 10th 7 updown ATLAS Preliminary

Tile calorimeter - illustration of performance: This picture shows the 8-fold structure in  of the beam splash events recorded on the 10th of September. The structure is due to the End Cap toroid material in front of TileCal for particles coming from the C-side. The up -down asymmetry is also due to the material in front of the detector. 8 updown ATLAS Preliminary

9 Tile calorimeter – test beam results: The response to electrons – Tilecal EM scale factor (1.050±0.003 pC/GeV) The energy resolution for pions impinging on the calorimeter at |η| =0.35, as a function of the beam energy. Data (full circles) are in reasonable agreement ‚with MC simulation results (open squares). ATLAS Preliminary

10 Monitored Drift Tubes 98.5% chambers operational 98.3% channels working Aim: 99.8% after shutdown Muon system MDT, CSC: precision tracking; TGC, RPC: trigger,  coordinate Cosmic muon map reconstructed by off-line RPC standalone muon monitoring projected on surface (y=81m). ATLAS Preliminary

11 Forward detectors LUCID (Luminosity Cerenkov Integrating Detector) at 17 m 2009: ZDC (Zero Degree Calorimeter ) at 140 m, 2010: ALFA (Absolute Lumi- nosity for ATLAS) at 240 m LUCID is a running detector in advanced status of commissioning; nevertheless, some consolidation and repairs are ongoing during the shutdown period LUCID signal, Sept. 10, Important for heavy ions, significant contribution from HI group

Data acquisition – cosmic events 12 ATLAS Preliminary

13 Heavy Ion Physics with the ATLAS Detector at the LHC Some selected results from the forthcoming Physics Performance Report More in parallel talks: Jets by Nathan Grau Quarkonia & Z 0 by Marzia Rosati Direct photons by Mark Baker

ATLAS calorimetry - full azimuthal acceptance Tracking in 2T solenoid Muons Photons Jets 100 GeV jet depositing energy Overview of ATLAS acceptance 14

Tracking Tracking efficiency and fake rate in |  | < 1 extracted from a sample of central (b=2 fm) HIJING events produced with quenching effects turned off in the ATLAS tracking system. Acceptable efficiency of about 70%, negligible fake rate above 1 GeV/c Top: Tracking efficiency as a function of pseudorapidity for tracks with 3 < p T < 8 GeV extracted from the same central sample of events. Bottom: Fake rate as function of pseudo- rapidity for the same tracks as above. Negligible dependence on  15 ATLAS Preliminary

Elliptic Flow Transverse momentum dependence of the reconstructed v 2 : from the event plane method (squares) two-particle correlations (stars) the Lee-Yang Zeros method (triangles) input flow as extrapolated from RHIC data (line) Thanks to complete azimuthal coverage we can well reproduce the input, different methods offer sensitivity to non-flow effects 16 ATLAS Preliminary Pb+Pb  s = 5.5 TeV/A b = 2.3 fm b=7.0 fm b=10.7 fm

Jets … elucidating the jet energy loss Parallel talk by Nathan Grau 17 Fragmentation function: D(z) Reliable reconstruction of D(z): Reconstructed tracks with p T > 2 GeV matching calorimeter jets The scale of possible modifications of fragmentation function – comparison of PYTHIA and PYQUEN We can measure jet quenching of the size simulated by PYQUEN ATLAS Preliminary

18 Dimuon Measurements … quarkonia, Z 0 Parallel talk by Marzia Rosati Background muons from open charm and beauty decays, from hadron in-flight decays before absorption in the calorimeter and from punch- through hadrons which can be reconstructed as muons. Error bars show statistical errors only. Di-muon invariant mass distribution as expected for one month of data, taking into account acceptance and efficiency, for decay muons in the barrel region only (|  | < 1).   in one month running at nominal luminosity (0.5 nb -1 ) ATLAS Preliminary  Mass Resolution 120 MeV, sufficient the separate  states

19 Direct Photons & Photon-Jet Correlations Parallel talk by Mark D. Baker The performance of the shower shape cuts and isolation cuts on PYTHIA di-jets embedded into b = 2 fm Pb+Pb events: Background greatly suppressed! ATLAS Preliminary

20 Summary ATLAS is fully operational, recorded several hundred million cosmic events Ongoing activities enable further detector improvements, calibration, refinement of monitoring, software tools Extensive preparations for Pb+Pb program show a promissing performance of ATLAS for heavy ion beams. We will participate in initial p+p data taking to get reference data for heavy ion program and to tune the analysis techniques.

21 Sources of further information ATLAS Public Results The ATLAS Experiment at the CERN Large Hadron Collider The ATLAS Collaboration, G Aad et al 2008 JINST 3 S08003