the status of the atlas experiment dr alan watson university of birmingham on behalf of the atlas...

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


LHC Point 1


ATLAS


ATLAS Installation


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


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)


The Inner Detector


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


Cosmic Tracking


Cosmic Track Statistics


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


SCT Commissioning

Track residuals with

preliminary aligned geometry

Similar efficiencies are measured in endcaps

SCT Barrel layer hit

efficiencies


Pixel Commissioning

Measurement of Lorentz angle Important for reaching ultimate

precision MC prediction ~224 mrad


Calorimeters


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


LAr Cosmic Commissioning


LAr Noise & Stability


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


Muon Spectrometer


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


Trigger and Precision Chambers

Hit correlation between barrel

precision and trigger chambers

Correlation between tracks from

endcap trigger and precision

chambers


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


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.


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.


Beam Splash Events

Tertiary Collimators

@ 140 m

Beam Pickups

@ 175 m

Minimum Bias

Trigger Scintillators


Beam Splash EventsMany TeV of energy deposited


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.


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


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

the status of the atlas experiment dr alan watson university of birmingham on behalf of the atlas...

Documents

msualan watsondis

shutdownalan watsondis

ratealan watsondis

cosmic trackingalan

inner detectoralan watsondis

tile hadronic h

presampler h

dead channels