cms vs atlas overview - cern · 4/13/09 cms vs atlas 1 cms vs atlas comparison of detectors...
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4/13/09 CMS vs ATLAS 1
CMS vs ATLAS
Comparison of Detectors(Source: Annu. Rev. Nucl. Part. Sci. 2006. 56:375–440.
“General-Purpose Detectors for the Large Hadron Collider”)
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ATLAS Overview
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CMS Overview
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Main Design Parameters Comparison
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Main Design Choices
• CMS– Invested in highest possible magnetic filed: 4T– Inner tracker consisting of all silicon detectors
• ATLAS– Invested much in three superconducting toroid magnets and a set
of precise muon chamberso “This system provides a stand-alone muon momentum measurement”
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PID
• CMS– Electrons
o ECAL
• ATLAS– Electrons
o ECAL, and matching between the E,p measured by ECAL and trackero Also enhenced by ATLAS TRT’s ability to separate electrons from
charged pions
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Magnet Systems
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Magnet Systems
• CMS– A single magnet with “a high magnetic field in the tracker volume
for all precision momentum measurements, and a high enoughreturn flux in the iron outside the magnet to provide a muon triggerand a second muon momentum measurement.”
• ATLAS– Driven by the goal to achieve a high-precision stand-alone
momentum measurement of muons --- “achieved using anarrangement of a small-radius thin-walled solenoid integrated intothe cryostat of the barrel ECAL, surrounded by a system of threelarge air-core toroids, situated outside the ATLAS calorimetersystems, and generating the magnetic field for the muonspectrometer.”
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Magnet Parameters Comparison
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Inner Tracking Systems
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Tracking System Parameters Comparison
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Pixel Detector Comparison
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Calorimetry
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ATLAS Calorimeter Overview
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CMS Calorimeter Overview
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Calorimetry Main Differences
• CMS– The full EM calorimetry and most of its hadronic alorimetry are
situated inside the solenoid coil and therefore bathed in the strong4 T magnetic field
– HCALo The strong constraints imposed by the CMS solenoid have resulted in
a barrel hadronic calorimeter with insufficient absorption (~ 7absorption lengths). So a tail catcher (HO) has been added around thecoil to complement the HB. But still, over-all, CMS jet resolution isworse than ATLAS.
• ATLAS– ATLAS solenoid is located just in front of the barrel ECAL,
resulting in significant energy loss by electrons and photons in thematerial in front of the active ECAL
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ECAL Main Parameters
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HCAL Main Parameters
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ECAL Performance Comparisons
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HCAL Performance Comparison
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Muon System
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ATLAS Muon System
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CMS Muon System
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Main Parameters
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ATLAS Muon Measurement Performance
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CMS Muon Measurement Performance
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Summary of Muon Performance