the status of the atlas experiment dr alan watson university of birmingham on behalf of the atlas...
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The Status of the ATLAS The Status of the ATLAS
ExperimentExperiment
Dr Alan WatsonDr Alan WatsonUniversity of University of BirminghamBirminghamon behalf of theon behalf of the ATLAS CollaborationATLAS Collaboration
Alan WatsonAlan Watson DIS 2009, 26/03/09DIS 2009, 26/03/09 22
The Large Hadron ColliderThe Large Hadron Collider
ATLASATLAS
CMSCMS
ALICE
LHCbLHCb
Design parameterss = 14 TeVL = 1034 cm-2s-1
40 MHz bunch-crossing rate
Initial operations = 10 TeVL = 10311032 cm-2s-1
1340 MHz bunch-crossing rate
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LHC Point 1
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ATLAS
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ATLAS Installation
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Commissioning started in 2005, in
parallel with installationTest channel mappings and timing
Identify dead and noisy channels, and
fix where possible
Verify stability of hardware during
operation
Gain experience in detector operation
and control, data acquisition,
reconstruction and analysis
Develop and test monitoring tools
Understand and improve detector
performance Detector alignment Initial calibrations
Commissioning
Commissioning dataPedestal and calibration runs
Cosmic ray events
Single beams and “beam splash” events
pp collisions 2009
Most cosmic data were taken in Autumn 2008
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Combined Cosmic RunningAlignment across different detectors
Hit efficiency measurements
Wide energy range
ET spectrum from cosmic events – Sum of all cells with |E| > 2– MC normalised to data in range 100-300
GeV– Excess at highest ET possibly due to air
showers (not included in simulation)
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The Inner Detector
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Inner Detector Components
SCT (Semiconductor tracker)4 double layers of strips in barrel. 9 in
endcaps.
4088 modules, 80 m strips, 6M
channels.
resolution 17 m580 m
>99% of barrel & >97 % of endcap
modules operational
Hit efficiency > 99%, noise occupancy
4.5-510-5
TRT (Transition Radiation Tracker)4mm straw tubes with 35m anode wiresTransition radiation gives e-p separation between 0.5 < E < 150 GeV73 barrel layers, axial straws2160 layers of radial straws in forward region, arranged in 20 discs98% of channels operationa.
Pixels3 layers in barrel & endcap
pixel size 50 m400 m
resolution 10 m110 m
80 M channels, > 95%
operational
Hit efficiency > 98%,
Noise occupancy 510-9
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Cosmic Tracking
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Cosmic Track Statistics
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TRT Commissioning
Cosmic shower in TRT,
showing “bubble-chamber
like” tracking
Measurement of turn-on of transition
radiation for cosmic ray muons. Good agreement with test beam results
confirms detector working properly
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SCT Commissioning
Track residuals with
preliminary aligned geometry
Similar efficiencies are measured in endcaps
SCT Barrel layer hit
efficiencies
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Pixel Commissioning
Measurement of Lorentz angle Important for reaching ultimate
precision MC prediction ~224 mrad
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Calorimeters
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ATLAS CalorimetersLAr Electromagnetic (|| < 3.2)
Pb-LAr accordion structure3 longitudinal samples || < 2.5presampler || < 1.8
LAr Endcap Hadronic (1.5 < || < 3.2) Cu-LAr structure, 4 longitudinal samples
LAr ForwardW/Cu rods & matrix, thin LAr gaps.3 longitudinal samples.
Tile Hadronic (|| < 1.7)Fe-scintillating tile structure3 longitudinal samples
EM energy resolution(E)/E = 10%/E 0.7 %
Hadronic energy resolution (jets)(E)/E = 50%/E 3 % (|| < 3.2)(E)/E = 100%/E 10 % (|| > 3.2)
StatusLAr: 0.02% dead channels (+ 0.9% recoverable). ~0.003% noisy channelsTile: ~1.4% dead channels, being repaired during shutdown
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LAr Cosmic Commissioning
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LAr Noise & Stability
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Tile Calorimeters
Tile Cell Noise vs eta Variation due to power distribution
Muon dE/dx from single beam data Horizontal muons provide test of tile
module intercalibration
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Muon Spectrometer
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Muon Spectrometer
Spectrometer performanceBdl = 1.5 - 5.5 TM (||<1.4)Bdl = 1 - 7.5 TM (||>1.6)Standalone resolution:
pT/pT < 10% up to 1 TeV
Precision Chambers ( 2.5)Monitored Drift Tubes (MDT)
1088 chambers, 330k channels 99.8% of chambers operational 0.1% dead channels (+ 1%
recoverable)Cathode Strip Chambers (CSC)
32 chambers, 31k channels. 2d readout
100% chambers operational <0.1% dead channels
Spatial resolution 35-40 mOptical alignment system: 12232 sensors
Trigger Chambers ( 2.4)Resistive Plate Chambers (RPC)
544 chambers, 359k channels 70% operational (goal 99.5% 2009) < 2% dead strips
Thin Gap Chambers (TCG) 3588 chambers, 318k channels 99.8% operational , <0.01 % dead channels
2d readout. Spatial resolution 5-10 mm, time resolution < 10 ns
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Trigger and Precision Chambers
Hit correlation between barrel
precision and trigger chambers
Correlation between tracks from
endcap trigger and precision
chambers
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Cosmic Muon Tracks
RPC tracks projected onto
cavern surface Access and lift shafts visible
Momentum difference between ID
and lower muon spectrometer Measures energy loss in calorimeters
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Trigger and DAQLevel-1 Trigger
Completely installedRate tests to 40 kHz, improve to nominal 75 kHz in 2009Fine timing of triggers in progress
High-Level Triggers (Level-2 & Event Filter)Current configuration
850 PCs in 27 racks (can be used as L2 or EF)
Capable of 60 kHz sustained rate
Final configuration 500 PCs for L2, 1800 PCs for EF (PC: 8
cores, 2.5 GHz, 2 GB RAM per core) 17 Level-2 racks, 67 EF racks (28 racks
configurable) Finalisation will be luminosity-driven
HLT tracking algorithms used to enrich cosmic samples for inner detector studies.
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Trigger Commissioning
Energy correlation between L1 calo
trigger and precision readout Random phase of cosmics broadens
trigger resolution
Muon trigger time from beam data– Difference in endcaps due to ToF– Narrow peaks mean timing otherwise
good at ~1 BC level.
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Beam Splash Events
Tertiary Collimators
@ 140 m
Beam Pickups
@ 175 m
Minimum Bias
Trigger Scintillators
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Beam Splash EventsMany TeV of energy deposited
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Trigger Timing with Single Beams
L1 trigger timing distribution, Sep 10th
BPTX trigger for stable time reference wrt LHC (BC 0)Poor beam quality – large numbers of muon and calorimeter triggersTwo-peak structure in TGC (endcap muon) trigger due to time of flight of muons
length of ATLAS ~5 bunch crossings!
L1 trigger timing distribution, Sep 12th
Triggered by MBTS (BC 0), which had been timed in relative to BPTX
good overlap between these triggers
Few other triggers – indication of improved beam quality.RPC (barrel muon) trigger had not been timed in prior to this run.
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Calorimeter Timing with Beam
Tile signal timingTime dispersion
within partitions ~2ns
Differences between
partitions < 1 BC
Raw timing TOF corrected
Horizontal muons from halo & splash provide checks on timing
LAr physics vs
calibration pulse timingMeasure time from pulse
profile + TOF
Predict timing from
calibration pulses +
cables
Most agree < 2ns
Alan WatsonAlan Watson DIS 2009, 26/03/09DIS 2009, 26/03/09 3030
Status of the ATLAS Experiment
Commissioning of the ATLAS detector
started more than 3 years ago
Large numbers of cosmic events taken with
full detector in 2008
ATLAS successfully took beam data in 2008
Cosmic and beam data very useful for
commissioning, calibration, timing and
alignment
Detector studies continue through the
shutdown
ATLAS was ready for collisions in 2008
…
… we will be in better shape in
2009