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Use of G EANT 4 in CMS

Use of G EANT 4 in CMS. AIHENP’99 Crete, 12-16 April 1999 Véronique Lefébure CERN EP/CMC. Content. The CMS Experiment The G EANT 4 Toolkit CMS first experience using G EANT 4 Summary. CMS: Compact Muon Solenoid. CERN, LHC, 2005 ~20000 particles / 25 nanoseconds

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Use of G EANT 4 in CMS

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  1. Use of GEANT4 in CMS AIHENP’99 Crete, 12-16 April 1999 Véronique Lefébure CERN EP/CMC

  2. Content • The CMS Experiment • The GEANT4 Toolkit • CMS first experience using GEANT4 • Summary Véronique LEFEBURE CERN EP/CMC

  3. CMS: Compact Muon Solenoid • CERN, LHC, 2005 • ~20000 particles / 25 nanoseconds • Complex detector, 22 m long, 15 m diameter • World-wide collaboration of ~ 1600 physicists Véronique LEFEBURE CERN EP/CMC

  4. The CMS detector Muon system Solenoid Electromagnetic calorimeter Central tracking Beam-Pipe Hadron calorimeter Véronique LEFEBURE CERN EP/CMC

  5. CMS Simulation Needs Simulation is needed for • 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 Véronique LEFEBURE CERN EP/CMC

  6. OSCAR (GEANT4) ORCA Xout ΔE Xin Clusterization of Digi’s +Pattern Recognition Simulation of the Detector Response Reconstruction Digitization Tracking Track RHIT DIGI HIT Véronique LEFEBURE CERN EP/CMC

  7. The GEANT4 Toolkit1. Introduction • GEANT4.0.0 was released in January 1999 : 4 year R&D, > 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 Véronique LEFEBURE CERN EP/CMC

  8. The GEANT4 Toolkit2. 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 Véronique LEFEBURE CERN EP/CMC

  9. The GEANT4 Toolkit3.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 Véronique LEFEBURE CERN EP/CMC

  10. The GEANT4 Toolkit4. Architecture GUI & UI RUN Visualization READOUT EVENT GENERATORS ODBMS DIGI TRACKING PHYSICS HITS TRACK GEOMETRY PARTICLE Utilities CAD FIELDS MATERIAL Véronique LEFEBURE CERN EP/CMC

  11. CMS Geometry Simulation:1.Architecture Barrel MSGC Tracker Tracker CMS Barrel Si Strip Barrel Si Pixel Beam-Pipe Muon System Forward MSGC Forward Si Pixel Calorimeters Forward Si Strip Véronique LEFEBURE CERN EP/CMC

  12. CMS Geometry Simulation:1.Architecture (cont’d) Services Support Barrel Si Pixel Cables • Cooling system • Set of Replicated structure made of • Support • Set of Replicated assembly made of • sensitive volume • electronics • cables X 2 layers Véronique LEFEBURE CERN EP/CMC

  13. CMS Barrel Si Pixel GEANT4.0.0 max. radius = 11 cm length = 60 cm Véronique LEFEBURE CERN EP/CMC

  14. 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 construct set sensitivity set visual attributes CMSDetector construct input file list of daughters BarrelPixel specific parameters G4BarrelPixel specific shapes Véronique LEFEBURE CERN EP/CMC

  15. CMS Geometry in GEANT4current 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 Véronique LEFEBURE CERN EP/CMC

  16. 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) Véronique LEFEBURE CERN EP/CMC

  17. 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) Véronique LEFEBURE CERN EP/CMC

  18. CMS Magnetic Field Map G4FieldManager 1 1 .. n G4Field G4MagneticField CMSMagneticField G4UniformMagneticField G4CMSMagneticField Véronique LEFEBURE CERN EP/CMC

  19. Magnetic Field in CMS Véronique LEFEBURE CERN EP/CMC

  20. 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 Véronique LEFEBURE CERN EP/CMC

  21. Muon mult. scattering 10 GeV muons Transverse displacement after 100 cm iron GEANT3.21 : GEANT4.0.0 : mm 100 GeV muons mm Véronique LEFEBURE CERN EP/CMC

  22. Muon energy loss 10 GeV muons Energy loss in 100cm iron GEANT3.21 : GEANT4.0.0 : MeV 100 GeV muons MeV Véronique LEFEBURE CERN EP/CMC

  23. HCAL (H2 1996) Test-Beam Setup 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 152 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 Scintillators: 2 mm passive Plastic 4 mm active Plastic 1 mm passive Plastic 64 cm x 64 cm Véronique LEFEBURE CERN EP/CMC

  24. G4 Hadronic showers Véronique LEFEBURE CERN EP/CMC

  25. 50 GeV pion shower Véronique LEFEBURE CERN EP/CMC

  26. 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 Véronique LEFEBURE CERN EP/CMC

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