Transcript Muon Identification in CMS

Project Presentations
August 5th, 2004
Andrew Wagner
CERN summer student 2004
Supervisor: Norbert Neumeister
Introduction
• Research
– Design an algorithm capable of identifying tracks as Muons based on
information supplied by the CMS Calorimeters and Muon system
• CMS detector
– Calorimetry
• Electromagnetic Calorimeter (Ecal)
• Hadronic Calorimeter (Hcal and HO)
– Muon system
• Drift Tubes (DT)
• Cathode Strip Chambers (CSC)
• Resistive Plate Chambers (RPC)
•
Motivation:
– Muon Identification complements Muon Reconstruction for physics analysis
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Compact Muon Solenoid Detector
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Muon Detectors
Three types of gaseous particle detectors for muon identification:
• Drift Tubes (DT) in the central barrel region
• Cathode Strip Chambers (CSC) in the endcap region
• Resistive Plate Chambers (RPC) in both the barrel and endcaps
The DT and CSC detectors are used to obtain a precise measurement of
the position and thus the momentum of the muons, whereas the RPC
chambers are dedicated to providing fast information for the Level-1 trigger
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Muons in CMS
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Approach
•
Strating point: Reconstructed Tracks in Tracker
– First Step: extrapolate reconstructed track to calorimeter and muon system taking
into account the magnetic field and energy loss and multiple scattering
•
Energy deposition in calorimeters
– Muons are Minimum Ionizing Particles (MIPs) and leave a distinctive signal in the
Ecal, Hcal and HO that can be cut on
– A sample of Monte Carlo generated single muons is compared to a sample of jets
for the purpose of determining this cut
•
Muon System
– Identification can be made based on reconstructed Hits, and Segments
– Both Hits and Segments are multidimensional objects (1-4) which are the
measurements used to perform the track fit (5 parameters)
– Compatibility of Hits and Segments with a Track is determined using a 2 criterion
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Ecal Barrel and Endcap
Muon Sample
Expected MIP energy in Barrel ~ 300 MeV
Threshold : 60 MeV per Crystal
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Expected MIP energy in Endcap ~ 400 MeV
Threshold : 150 MeV per Crystal
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Hcal Signal and Background
Blue: Jet Sample
Red: Muon Sample
Expected MIP energy in Barrel ~ 3 GeV
Expected MIP energy in Barrel ~ 2 GeV
Threshold : .5 GeV
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Threshold : .5 GeV
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HO Signal and Noise
Muon Sample
HO only in Barrel Expected MIP energy ~ 1 GeV varies with Eta
High Thresholds ~.5 GeV applied at readout
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2 Distribution Muon DT Hits
Muon Sample: Example shows DT Hits
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Conclusions
The MIP signal in the Ecal and Hcal is an
efficient means of identifying Muons and can be
used to compliment Muon Reconstruction
Understanding the 2 and probability
distributions for hits in the Muon Stations will
allow for a further improvement in efficiency for
Muon identification
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Thanks
Norbert Neumeister
Jean Krisch
The University of Michigan, Ford, and
CERN
All of my fellow students for helping to
make this summer so much fun!
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