Geant4 in production: status and developments

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Geant4 in production status and developments

• John Apostolakis (CERN)
• Makoto Asai (SLAC)
• for the Geant4 collaboration

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1. Geant4s in HEP, production

• HEP Experiments in large scale production
• BaBar (2001)
• CMS (2003)
• ATLAS (2004)
• LHCb (2004)
• Used in many existing experiments
• KamLAND, Borexino, HARP,
• Used to study future experiments
• ILC, NA48/3 (PA326),

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Geant4s widespread use

• Imaging, radiotherapy, dosimetry
• PET and SPECT imaging (GATE),
• brachytherapy, hadrontherapy,
• Space satelites and planetary missions
• XMM, INTEGRAL, Bepe Colombo, LISA,
• Radiation assessment, dosimetry
• LHCb, Electronics (TCAD),

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2. Geant4 improvements

• Improved stability of EM energy deposition,
  resolution
• From revision of electron transport (Multiple
  scattering)
• Enables better accuracy at higher cuts - with
  less CPU
• Extensions to geometry modeler
• Ability to revise many particle properties
• Refinements, improvements in hadronics
• Physics Lists

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Summary

• Improvements in multiple scattering process
• Addressing issues with electron transport
• Speedups for initialisation/navigation
• Option to only re-optimise parts that change with
  run
• New voxelisation options being studied for
  regular geometries
• Overlap checks at geometry construction
• Revised implementation of particles
• Impacting advanced users, customizing
• Refinements in hadronic physics

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FLUKA and the Virtual Monte Carlo

• Andreas Morsch
• For the ALICE Offline Group
• CERN, Geneva, Switzerland

Computing in High Energy and Nuclear
Physics 13-17 February 2006, T.I.F.R., Mumbai,
India
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Integration of FLUKA into detector simulation
frame-work

• Advantages
• Full detector simulation and radiation studies
  using the same detailed geometry
• Re-use of code for detector response simulation
  as already developed for Geant3
• Integration has been achieved using the
• Virtual Monte Interface3 and
• The Root geometry modeler TGeo4

3http//root.cern.ch/root/vmc/VirtualMC.html 4http
//root.cern.ch
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Virtual MC Concept

• Transport MC transparent to the user application
• Base class TVirtualMC

User Code
VMC
TGeo
Input
GEANT3 VMC
GEANT3
Particles Hits
GEANT4
GEANT4 VMC
FLUKA
FLUKA VMC
Output
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Virtual Monte Carlo (VMC)
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Validation

• Validation of geometry navigation via TGeo
• Standard benchmark tests provided by FLUKA
  authors
• Technical validation of the VMC implementation
• Comparison with G3 results
• Physics validation
• Comparison with test-beam data

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Electron transport in thin layers

• 1000 electrons at 1 MeV, EM cascades
• Same final random number after simulations with
  FLUKA native and TFluka
• The same for all 3 tested examples

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FLUKA/G3 Comparison

• Good agreement where it is expected
• Photons in electromagnetic shower

FLUKA VMC G3 VMC
log10(E/GeV)
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Comparison with test-beam data ongoing
Silicon Pixel Detector
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Conclusions

• FLUKA VMC implementation completed
• Testing well advanced
• TGeo/FLUKA validation completed
• Good agreement with G3 and Testbeam
• FLUKA VMC will be used in the next ALICE Physics
  data challenge

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