Introduction to ATLAS

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Introduction to ATLAS
ECal and Muon Chamber

• Dan Ventura
• 3/09/2006

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Calorimeters
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Calibrating the ECal

• Pre-Calibration
• Use test beams, radiation sources
• Consistency between towers 5

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Z ee-

• Production
• 50,000 events for L70 pb-1
• (Cuts PTgt15 GeV, hlt2.5)
• Set absolute mass scale
• Fit to known Z line-shape
• Fix energy scale to .5

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Muon Chambers
Monitored Drift Tubes
Barrel Toroid Coils
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Tracking Muons

• 370,000 Monitored Drift Tubes (MDT)
• Drift time distance
• Muon hits 6-8 MDTs per chamber

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Difficulties with Muon System

• Open air-core toroids produce Inhomogeneous field
• Complicated Lorentz force behavior, making
  momentum more difficult to measure
• Large size (22m in diameter, 44m long)
• Introduce extrapolation uncertainties
• Muons traverse more material

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Magnetic Field

• Field measured throughout spectrometer by 3D Hall
  probes
• 5000 throughout the volume
• Simulation has shown the field can be determined
  to .2

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Extrapolation Uncertainties

• Precision chambers aligned to 30 mm
• Reconstruction software takes into account
  material traversed
• Provides correction to muon energy

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Muon Chamber Calibration

• Cosmic ray muons
• Occur at 0.5 Hz to 30Hz, 106 cosmic events
  should be collected before 1st physics run
• Calibrate muon chambers with no magnetic field
• Use standard candle Z mm-
• set energy scale

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Muon Fake Rates

• High pT muons produce secondary particles
• 100 GeV efficiency95
• fake rate0.2
• 1 TeV efficiency80
• fake rate1.8

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References

• 1. D. Green, arXivhep-ph/0601038 v1 Jan 05, 2006
• 2. F. Gianotti M. Mangano, arXivhep-ph/0504221
  v1 April 25, 2005
• 3.M. Woudstra, Precision of the ATLAS Muon
  Spectrometer, CERN Thesis, April 2002
• 4. ATLAS Collaboration, Technical Design Report
• 5. M. Delmastro, CTB04 LAr EM Performances, Feb.
  23, 2006