1. Use of G EANT 4 in CMS AIHENP’99 Crete, 12-16 April 1999 Véronique Lefébure CERN EP/CMC

2. AIHENP’99 Crete, 12-16 April 99 Véronique LEFEBURE CERN EP/CMC 2 Content The CMS Experiment The G EANT 4 Toolkit CMS first experience using G EANT 4 Summary

3. AIHENP’99 Crete, 12-16 April 99 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

4. AIHENP’99 Crete, 12-16 April 99 Véronique LEFEBURE CERN EP/CMC 4 The CMS detector Central tracking Electromagnetic calorimeter Hadron calorimeter Solenoid Muon system Beam-Pipe

5. AIHENP’99 Crete, 12-16 April 99 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

6. AIHENP’99 Crete, 12-16 April 99 Véronique LEFEBURE CERN EP/CMC 6 OSCAR ( G EANT 4 ) ORCA HIT Tracking X in X out ΔE ΔE Digitization DIGI Simulation of the Detector Response Clusterization of Digi’s +Pattern Recognition Reconstruction Track RHIT

7. AIHENP’99 Crete, 12-16 April 99 Véronique LEFEBURE CERN EP/CMC 7 The G EANT 4 Toolkit 1. Introduction –G EANT 4.0.0 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

8. AIHENP’99 Crete, 12-16 April 99 Véronique LEFEBURE CERN EP/CMC 8 The G EANT 4 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

9. AIHENP’99 Crete, 12-16 April 99 Véronique LEFEBURE CERN EP/CMC 9 The G EANT 4 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

10. AIHENP’99 Crete, 12-16 April 99 Véronique LEFEBURE CERN EP/CMC 10 The G EANT 4 Toolkit 4. Architecture RUN EVENT TRACKING TRACK GEOMETRY FIELDS READOUT DIGI HITS CAD GENERATORS PHYSICS PARTICLE MATERIAL GUI & UI Visualization ODBMS Utilities

11. AIHENP’99 Crete, 12-16 April 99 Véronique LEFEBURE CERN EP/CMC 11 CMS Geometry Simulation: 1.Architecture Tracker Beam-Pipe Calorimeters Muon System CMS Tracker Barrel Si Pixel Forward Si Pixel Forward Si Strip Barrel Si Strip Forward MSGC Barrel MSGC

12. AIHENP’99 Crete, 12-16 April 99 Véronique LEFEBURE CERN EP/CMC 12 CMS Geometry Simulation: 1.Architecture (cont’d) Barrel Si Pixel Support Cables Services Cooling system Set of Replicated structure made of Support Set of Replicated assembly made of sensitive volume electronics cables X 2 layers

13. AIHENP’99 Crete, 12-16 April 99 Véronique LEFEBURE CERN EP/CMC 13 CMS Barrel Si Pixel G EANT 4.0.0 max. radius = 11 cm length = 60 cm

14. AIHENP’99 Crete, 12-16 April 99 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 G EANT 4 geometry, only knowledge of shapes. CMSDetector construct input file list of daughters BarrelPixel specific parameters G4BarrelPixel specific shapes G4Able construct set sensitivity set visual attributes

15. AIHENP’99 Crete, 12-16 April 99 Véronique LEFEBURE CERN EP/CMC 15 CMS Geometry in G EANT 4 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

16. AIHENP’99 Crete, 12-16 April 99 Véronique LEFEBURE CERN EP/CMC 16 CMS Materials G EANT 4: –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)

17. AIHENP’99 Crete, 12-16 April 99 Véronique LEFEBURE CERN EP/CMC 17 CMS Rotation Matrices G EANT 4: –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)

18. AIHENP’99 Crete, 12-16 April 99 Véronique LEFEBURE CERN EP/CMC 18 CMS Magnetic Field Map G4Field G4MagneticField G4UniformMagneticFieldG4CMSMagneticField CMSMagneticField G4FieldManager 11.. n

19. AIHENP’99 Crete, 12-16 April 99 Véronique LEFEBURE CERN EP/CMC 19 Magnetic Field in CMS

20. AIHENP’99 Crete, 12-16 April 99 Véronique LEFEBURE CERN EP/CMC 20 Muon Physics with G EANT 4 Comparisons between G EANT 3.21and G EANT 4.0.0 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 G EANT 3, process missing, correction factors missing G EANT 4 uses more up-to-date cross-section values –Results going to be compared with experimental data

21. AIHENP’99 Crete, 12-16 April 99 Véronique LEFEBURE CERN EP/CMC 21 Muon mult. scattering Transverse displacement after 100 cm iron G EANT 3.21 : G EANT 4.0.0 : 10 GeV muons 100 GeV muons mm

22. AIHENP’99 Crete, 12-16 April 99 Véronique LEFEBURE CERN EP/CMC 22 Muon energy loss Energy loss in 100cm iron G EANT 3.21 : G EANT 4.0.0 : 10 GeV muons 100 GeV muons MeV

23. AIHENP’99 Crete, 12-16 April 99 Véronique LEFEBURE CERN EP/CMC 23 HCAL (H2 1996) Test-Beam Setup 123456789101112131415161718192021222324252627 1 Layer 1 : 2 cm Copper 2 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 152 cm Copper + 189 mm Plastic 64 cm x 64 cm

24. AIHENP’99 Crete, 12-16 April 99 Véronique LEFEBURE CERN EP/CMC 24 G4 Hadronic showers

25. AIHENP’99 Crete, 12-16 April 99 Véronique LEFEBURE CERN EP/CMC 25 50 GeV pion shower

26. AIHENP’99 Crete, 12-16 April 99 Véronique LEFEBURE CERN EP/CMC 26 Summary CMS has close to 2 year experience with alpha, beta and first public releases of G EANT 4 G EANT 4 will be used for full CMS simulation (OSCAR project) further validation tests of the physics processes simulated by G EANT 4 will be performed using test-beam data