Transcript No Slide Title

Use of GEANT4 in CMS
AIHENP’99
Crete, 12-16 April 1999
Véronique Lefébure
CERN EP/CMC
Content
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AIHENP’99
Crete, 12-16 April 99
The CMS Experiment
The GEANT4 Toolkit
CMS first experience using GEANT4
Summary
Véronique LEFEBURE
CERN EP/CMC
2
CMS:
Compact Muon Solenoid
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CERN, LHC, 2005
~20000 particles / 25 nanoseconds
Complex detector, 22 m long, 15 m diameter
World-wide collaboration of ~ 1600 physicists
AIHENP’99
Crete, 12-16 April 99
Véronique LEFEBURE
CERN EP/CMC
3
The CMS detector
Electromagnetic
calorimeter
Muon system
Solenoid
Central tracking
Beam-Pipe
Hadron
calorimeter
AIHENP’99
Crete, 12-16 April 99
Véronique LEFEBURE
CERN EP/CMC
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CMS Simulation Needs
Simulation is needed for
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detector engineering studies and optimization
determination of trigger logic
estimation of potential for physics discoveries
interpretation of the experimental data
simulation of
– detector geometry
– particle interactions in the detector material
– detector response
AIHENP’99
Crete, 12-16 April 99
Véronique LEFEBURE
CERN EP/CMC
5
OSCAR (GEANT4)
ORCA
Xout
ΔE
Xin
Simulation of the
Detector Response
Tracking
HIT
AIHENP’99
Crete, 12-16 April 99
Digitization
DIGI
Véronique LEFEBURE
CERN EP/CMC
Clusterization of Digi’s
+Pattern Recognition
Reconstruction
RHIT
Track
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The GEANT4 Toolkit
1. Introduction
– GEANT4.0.0 was released in January 1999 : 4 year R&D,
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> 100 physicists, engineers, computer scientists, ~40 institutes
Complete toolkit of electromagnetic and hadronic physics, solid
modeling, tracking, run and event generation, visualization, GUI
Designed and implemented with Object-Oriented technologies (C++)
Meeting requirements for LHC experiments
User extensible
ESA joint-project (spacecraft's and instrumentation design,
radiation shielding) + nuclear and medical applications
AIHENP’99
Crete, 12-16 April 99
Véronique LEFEBURE
CERN EP/CMC
7
The GEANT4 Toolkit
2. Functionality
– Description of the geometry and material composition of the detector
• CMS: several 100K physical volumes, ~50 different shapes,
~200 materials
– Particles are tracked through the detector, simulating their physics
interactions in matter and the effect of fields and boundaries on their
trajectories
• CMS: 4 T magnetic field
– Graphics, user interfaces, object storage
• CMS: storage of geometry information and simulated hits to be
used by ORCA
AIHENP’99
Crete, 12-16 April 99
Véronique LEFEBURE
CERN EP/CMC
8
The GEANT4 Toolkit
3.Physics
– Physics modeling
• is transparent to the user
• can be extended by the user
– Cross-sections and final states
• are computed separately from the tracking system
• can be split by energy range, particle type and material
– Cross-sections determine the tracking step length
– Use of an extensive system of units
AIHENP’99
Crete, 12-16 April 99
Véronique LEFEBURE
CERN EP/CMC
9
The GEANT4 Toolkit
4. Architecture
GUI & UI
RUN
READOUT
Visualization
EVENT
GENERATORS
DIGI
TRACKING
HITS
TRACK
PHYSICS
GEOMETRY
CAD
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FIELDS
ODBMS
PARTICLE
MATERIAL
Véronique LEFEBURE
CERN EP/CMC
Utilities
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CMS Geometry Simulation:
1.Architecture
Tracker
CMS
Tracker
Barrel Si Pixel
Beam-Pipe
Muon
System
Forward Si Pixel
Calorimeters
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Crete, 12-16 April 99
Barrel MSGC
Barrel Si Strip
Forward MSGC
Forward Si Strip
Véronique LEFEBURE
CERN EP/CMC
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CMS Geometry Simulation:
1.Architecture (cont’d)
Barrel Si Pixel
Services
Support
•Cooling system
•Set of Replicated structure made of
•Support
•Set of Replicated assembly made of
•sensitive volume
•electronics
•cables
Cables
X 2 layers
AIHENP’99
Crete, 12-16 April 99
Véronique LEFEBURE
CERN EP/CMC
12
CMS Barrel Si Pixel
GEANT4.0.0
max. radius = 11 cm
length = 60 cm
AIHENP’99
Crete, 12-16 April 99
Véronique LEFEBURE
CERN EP/CMC
13
CMS Geometry Simulation:
2.Implementation
– Mother-Daughter organization: construction is propagated
from mother to daughters
– First prototype: access to input data de-coupled from
construction of GEANT4 geometry, only knowledge of
shapes.
G4Able
CMSDetector
construct
input file
list of daughters
BarrelPixel
construct
set sensitivity
set visual attributes
specific parameters
G4BarrelPixel
specific shapes
AIHENP’99
Crete, 12-16 April 99
Véronique LEFEBURE
CERN EP/CMC
14
CMS Geometry in GEANT4
current status
• Beam Pipe
• Tracker
– Si Pixel Detectors
• Barrel Si Pixel
• Forward Si Pixel
– Si Strip Detectors
• Barrel Si Strip
– MSGC
• Barrel MSGC
• Calorimeters
– Electromagnetic Calorimeter
• Barrel ECAL
– Hadron Calorimeter
• Barrel HCAL
• Muon System
– Barrel Muon
AIHENP’99
Crete, 12-16 April 99
Véronique LEFEBURE
CERN EP/CMC
15
CMS Materials
• GEANT4:
– Materials defined by weight fractions or atom
proportions, of elements and/or materials
• CMS has developed:
– Material definition based on mixtures of elements
and/or mixtures of materials, by weight fraction,
volume fraction, atomic proportions.
 CMSMaterial and CMSMaterialFactory (input file)
AIHENP’99
Crete, 12-16 April 99
Véronique LEFEBURE
CERN EP/CMC
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CMS Rotation Matrices
• GEANT4:
– Matrix constructed from Identity, rotation axes and
angles (from CLHEP)
• CMS has developed:
– Matrix specified by polar and azimuthal angles of
the new axes.
 CMSRotationMatrixFactory (input file)
AIHENP’99
Crete, 12-16 April 99
Véronique LEFEBURE
CERN EP/CMC
17
CMS Magnetic Field Map
G4FieldManager
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1 .. n
G4Field
G4MagneticField
G4UniformMagneticField
AIHENP’99
Crete, 12-16 April 99
CMSMagneticField
G4CMSMagneticField
Véronique LEFEBURE
CERN EP/CMC
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Magnetic Field in CMS
AIHENP’99
Crete, 12-16 April 99
Véronique LEFEBURE
CERN EP/CMC
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Muon Physics with GEANT4
Comparisons between GEANT3.21and GEANT4.0.0 for
low/high energy muons going through 100 cm iron.
– Good agreement for E~10 GeV
– Differences at E~100 GeV as expected:
• limit of validity range of GEANT3, process missing, correction
factors missing
• GEANT4 uses more up-to-date cross-section values
– Results going to be compared with experimental data
AIHENP’99
Crete, 12-16 April 99
Véronique LEFEBURE
CERN EP/CMC
20
Muon mult. scattering
10 GeV muons
Transverse displacement
after 100 cm iron
GEANT3.21 :
GEANT4.0.0 :
mm
100 GeV muons
mm
AIHENP’99
Crete, 12-16 April 99
Véronique LEFEBURE
CERN EP/CMC
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Muon energy loss
10 GeV muons
Energy loss in 100cm iron
GEANT3.21 :
GEANT4.0.0 :
MeV
100 GeV muons
MeV
AIHENP’99
Crete, 12-16 April 99
Véronique LEFEBURE
CERN EP/CMC
22
HCAL (H2 1996) Test-Beam Setup
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152 cm Copper + 189 mm Plastic
Layer 1 : 2 cm Copper
Layers 2 to 7 : 3 cm Copper
Layers 8 to 21: 6 cm Copper
Layers 22 to 27: 8 cm Copper
AIHENP’99
Crete, 12-16 April 99
Scintillators: 2 mm passive Plastic
4 mm active Plastic
1 mm passive Plastic
Véronique LEFEBURE
CERN EP/CMC
64 cm x 64 cm
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G4 Hadronic showers
AIHENP’99
Crete, 12-16 April 99
Véronique LEFEBURE
CERN EP/CMC
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50 GeV pion shower
AIHENP’99
Crete, 12-16 April 99
Véronique LEFEBURE
CERN EP/CMC
25
Summary
• CMS has close to 2 year experience with alpha,
beta and first public releases of GEANT4
• GEANT4 will be used for full CMS simulation
(OSCAR project)
• further validation tests of the physics processes
simulated by GEANT4 will be performed using
test-beam data
AIHENP’99
Crete, 12-16 April 99
Véronique LEFEBURE
CERN EP/CMC
26