Geant4 status and results

1
Geant4 status and results

• John Apostolakis, CERN
• for Geant4 collaboration

2
Highlights

• Confrontation with data
• many results
• Status
• Overview of Geant4
• Developments since last CHEP
• New members
• new alternative physics models
• Plans

3
Confrontation with data

• Many comparisons made, and results published
• A lot of comparisons are ongoing, starting
• within the collaboration (eg in experiment
  groups)
• in other experiments, groups in other fields
• diverse uses (eg outer-space, medical, ..)
• often small groups

4
Electromagnetic processes

• All processes at least at level of Geant-3
• New process Transition radiation
• Multiple Scattering new model
• no path length restriction
• added lateral displacement
• measured effect on result
• Energy Loss two approaches
• two approaches differential and integral
• several alternatives PAI model (thin), Super
  E-loss
• Integration of cross section over Energy
• DE/E not constrained for e/e-
• hadronic resonances can be seen (future)

5
Shower profile

• 1 GeV electron
• in H2O
• G4,
• Data
• G3
• Very good agreement seen with the data

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Geant4 5 GeV electron in PbWO4 Geant3 --1
rad. len
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Sampling calorimeter

• Sampling calorimeter
• visible energy
• tests
• all EM processes for e-, e and photon
• Data from Sicapo Col. NIM A332 (85-90) 1993

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Changing cuts

• Results very stable with variation of cuts
• even track length
• Also see shower profiles for different cuts (next
  slide)
• between 10mm and 50 microns

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Multiple scattering

• Examples of comparisons
• 15.7 MeV e-
• on 19 mg/cm2 gold foil (8 um) figure
• 6.56 MeV proton
• on 93 microns Si
• 70 GeV/c proto

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Standard EM results summary

• Shower profiles in agreement with data
• Visible energy in calorimeters very good
• Great stability with changing cuts.
• Multiple scattering deviations agree
• With thanks to
• M. Maire, L. Urban, S. Giani

15
Low energy EM processes

• Photons, electrons down to 250 eV
• Xsec from evaluations
• with thanks to J. Stepanek
• CERN/ ESA
• A. Forti
• M.G. Pia
• P. Nieminen

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Low energy EM processes

• Protons, ions, antiprotons
• Ziegler or ICRU
• parameterisations
• M.G. Pia
• V. Ivanchenko
• G. Mancinelli
• S. Chauvie

17
Cuts production user

• Coherent production cuts
• validity range of models fully exploited
• kernel can enforce consistent production cuts
• yet processes can ask to override when they need
  to.
• treatment of boundary effects (Figures)
• Cuts in range rather than Energy
• Geant3 used cuts in Energy - inefficient
• significant gain in results quality vs CPU usage
• User can cut in Energy, track length, TOF ..

18
Hadronic processes

• Flexible approach
• variety models
• parameterised, data-driven and theoretical
• See subsequent talks
• Hadronic shower model framework (J.P. Wellisch)
• An intra-nuclear transport model (M.G. Pia)
• Pre- and equilibrium decays (V.Lara)

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Hadronic physics processes

• Inelastic and coherent elastic scattering
• Capture of neutral, strongly interacting
  particles by nuclei, and neutron-induced fission
• Processes at rest for long-living, stopping
  particles
• New parameterisations
• total cross-section p/n-N (0/14MeV to 20GeV),
• differential cross-section p-p (0.1MeV to 3GeV)
• Neutron transport (ENDF/B-VI)
• High Energy extensions
• using techniques from heavy ion generators, and
• cascade pre-equilibrium evaporation
• Many other small improvements

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High Energy K,pi on Al, Au
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Photon evaporation
MeV
MeV
Photon energy, discrete levels
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Parameterization/Fast Simulation

• Fast Simulation Manager
• Framework for parameterization
• Takes over from detailed simulation
• can return to detailed simulation (eg cracks)
• Can trigger on particle, volume, ..
• Parallel geometrical description
• BaBar developed Bogus based on this.

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Other processes

• Decay
• Optical processes
• Reflection, refraction, absorption
• Transportation
• interrogates geometry, field motion
• Low energy extensions,
• down to 250 eV for e-/g, proton, ions,
  anti-protons
• from ESA/CERN joint project

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Particles in geant4 1.0

• Ordinary particles
• have a corresponding class type (singleton)
• Nuclei are created dynamically
• Too many to create static objects
• Checking of properties of particles with PDG data
• www-pdg.lbl.gov/computer_read.html
• Mass, Width, Charge, Encoding

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Migration to STL

• Moved from RW Tools.h to STL
• by implementing RW containers used in STL
• STL versions supported
• Objectspace, g native
• Geant4 1.0 works only with STL
• retaining our RW interface
• Plans for full migration (deleting RW)
• under development (long timescale)

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Migration to ISO C

• Need to adapt to moving
• compilers, advanced users, STL
• New I/O library headers std namespace
• Deprecation of C-style headers
• ltmath.hgt, ltstdio.hgt, ltstdlib.hgt, ltstring.hgt,
  lttime.hgt
• Moved from Objectspace to native STL for ISO
• Code migrated, released to Geant4 collaboration
• (G. Cosmo, G.Garcia, G. Folger,
  )

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Geometry developments in 18 months

• Boolean solids (V.Grichine
  J.A.)
• new solids from Union, Intersection, Subtraction
• of two solids a transformation (optional)
• Revised g3tog4 (I.Hrivnacova, P. Arce
• fixed extended divisions, ( W.
  Lockman)
• Field
• tracking of spin (P.Gumplinger)
• ability to track in Electric field

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g3tog4

• Revised greatly in latest release
• able to create geometry of large experiment
  (eg L3)
• works with STL
• Auxiliary package to Geant4
• meant to facilitate utilisation of legacy setups
• in small scale (not full Geant 3.21 complexity)
• not as long term solution for experiments

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EM processes energy cut-offs
Geant3.21 10 keV EGS4, ITS3.0
1 keV Geant4 standard models -
Photoelectric effect 10 keV - Compton
effect 10 keV - Bremsstrahlung 1 keV -
Ionisation (d-rays) 1 keV - Multiple
scattering 1 keV Geant4 low-energy models 250
eV
ESA Space Environment Effects Analysis Section
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X-Ray Surveys of Asteroids and Moons
Cosmic rays, jovian electrons
Solar X-rays, e, p
Geant3.21
ITS3.0, EGS4
Courtesy SOHO EIT
Geant4
Induced X-ray line emission indicator of target
composition (100 mm surface layer)
C, N, O line emissions included
ESA Space Environment Effects Analysis Section
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New GEANT4 Collaboration

• Started Dec 98 with signing of MoU
• Labs, experiments, university groups
• contribute people (experts), money
• represented on management board
• Technical board
• Composed of
• Representatives of experiments (larger fraction)
• Other geant4 developers (coordinators)

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Geant4 in 1999

• January 1999 to April
• issued patches for urgent fixes
• Consolidation release 4.0.1
• released in July 1999
• it contains
• fixes, minor improvements
• a few models (low energy EM, string model)
• the ability to use STL instead of Rogue Wave

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Geant4 latest release

• The latest release was made on schedule
• on December 7th, 1999
• with additional physics models
• isotope production
• multi-fragmentation redesign/refinement
• with fixes, improvements and new functionality
• improved Super Energy Loss
• basic layer for support of ISO C compilers

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Support, Maintenance

• Support
• Welcome all problem reports
• via Web
• But new requirements support for members
• full service through their TSB representative.
• Others get best effort basis
• Each experiment/institute provides
• expertise or resources corresponding to what it
  requires from the collaboration

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Geant4 Context

• Geant4 project collaboration
• was developed by RD44 project
• RD44 ended with first production release
• version 4.0.0 in December 98
• New Geant4 collaboration
• for production service, maintenance and to
  continue to develop Geant4
• is made of experiments, laboratories institutes

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New members, groups

• The Geant4 collaboration has expanded, recently
  welcoming
• Jefferson Laboratory
• contributing CHIPS model
• Institute for Theoretical Physics of the
  University of Frankfurt
• contributing diverse cascade models
• IN2P3 taking over from Ecole Polytechnique

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Geant4 Capabilities

• Very powerful Geant4 kernel
• tracking, stacks, geometry, hits, ..
• Extensive transparent physics models
• electromagnetic, hadronic, (next talks)
• Additional capabilities/interfaces
• persistency, visualization, ...
• Surpasses Geant-3
• in nearly every respect

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Summary

• Productive year since 1st production release
• Many results of Geant4 versus data
• very good agreement seen
• even more comparisons are being made
• Geant4 has
• much power, flexibility and extensibility
• everything you could do in Geant-3 and interfaced
  packages

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Geant4 prerequisites

• Platforms
• HP, SUN, DEC
• native compilers.
• Linux g
• NT Visual C 6
• Class Libraries
• CLHEP 1.4
• In Geant4 1.0 must use STL
• ObjectSpace, g
• no longer support
• Rogue Wave Tools.h

• Visualization
• OpenGL, X, OpenInv
• DAWN, opacs
• Persistency
• Can run transient
• To store use a
• HepDB interface
• on top of ODMG std.

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THE END
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• G. Cosmo for BaBar

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Future developments

• Outlines of developments
• discussed at the Geant4 workshop (Sept 1999)

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Particles and Tracks Plans

• Isotope
• Agreements on
• Ion Name
• Arguments of GetIon method etc.
• G4VIsotopeTable
• a table of isotopes is necessary to implement
  Radioactive Decay
• Basic design

44
Geometry and Transportation

• Issues discussed in Parallel sessions
• Adding local fields
• Collected requirements, analysed consequences
• Global field and (optional) local field to
  override it.
• Persistency of detector description
• will add boolean solids in next release
• study material persistency create plan
• Geant3 to Geant4 detector conversion
• Reflecting a volume hierarchy a factory

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Geometry In progress

• STEP file reading
• enable association with materials
• BREP testing and code improvements
• Field further performance improvement
• geometrical optimisation with use of safety
• Deeper testing of CSG solids
• More consistency checks, regression tests

46
BREPS/ STEP Short/medium term plans

• Check correct reading of STEP description
  parameters and construction
• fix current deficiencies
• Add capability to write BREP geometry description
  to STEP file
• Enable association of material with solid (needed
  for creation of logical volumes)
• Visualization of BREPS
• Performance studies

47
Persistency Plans

• HepODBMS 0.3.0.1 / Objectivity 5.1
• HepVArray --gt ooVArray, Objectivity STL
• Support RD45 prototype "Espresso"
• Further documentation and examples
• More Geometry types
• Boolean, BREP, Parameterized Volume
• Consider persistency of materials

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Persistency Summary

• Persistency defines how Geant4 objects should
  interact with user's domain
• Current implementation is simplified
• Keep in sync with developments, eg in Geometry
• Could facilitate some operations of the users
• automated installation scripts, friendly
  documents, Espresso,
• Asking for more, clear requirements from users ..

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End of developments summary

• End of developmentsproto-section

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Geant4 kernel run/event

• Includes categories for run, event, track
• One computing process can have many runs

• Run
• each run has a fixed geometry event-generator
• can do many runs in one job / process

• Event
• Manages track creation
• Stacks for inactive tracks
• 3 default stacks
• very powerful
• no cost!

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Geant4 kernel tracking .

• Tracking is general
• same for all particle types
• different list of processes for each particle
• It messages
• sensitive detectors and user actions
• So anyone can add their physics model
• simply, without restrictions or problems

52
Geant4 kernel other

• Hits digitization
• Experiment specific hits
• Handles event pileup
• using new readout category
• Materials
• isotopes, elements,
• compounds, ...

• Particles
• properties from PDG
• Intercoms
• communicate
• between categories,
• from UI to kernel
• Geometry
• hierarchy or flat
• performant

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Geant4 geometry what it does

• Describes a Detector
• Hierarchy of volumes
• Many volumes repeat
• Volume sub-tree
• Up to millions of volumes for LHC era
• Import detectors from CAD systems

• Navigates in Detector
• Locates a point
• Computes a step
• Linear intersection
• Field propagation

54
Object Persistency Hits other

• To store hits, use object persistency
• Abstract interface
• ODBMS solution via RD45 (Objectivity)
• Tracker-type and calorimeter-type hits
• Saw minimal performance storage overhead
• Minimal modifications
• G4 kernel untouched
• Also store
• Trajectories, Runs,
• Events, Geometry

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EM Processes recent developments

• Several comparisons presented
• with data (and Geant3 simulation)
• standard EM processes
• showed
• good agreement with data (and G3.21 almost
  always)
• better agreement (than G3.21) in Fe/W calorimeter
• Super Energy Loss
• only simulate escaping particles ( use high
  cuts)

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Hadronic physics

• The goal A hadronic shower simulation tool-kit
  suitable for LHC experiments.
• Tunable code in the test-beam region
• Detailed neutron tracking at low energies
• Safe extrapolation beyond test-beam region
• Possibility to use variance reduction techniques
• Easy customizability and extendibility of the
  underlying physics modeling

57
Hadronics the Plan

• Re-use the experience encapsulated in at least
  one widely used package
• OO design to maximize extendibility and to enable
  distributed development
• Use of ENDF/B-VI data libraries for low energy
  neutron transport
• Use Pythia-7 and techniques developed for heavy
  ion generators for high energy interactions.
• Build in variance reduction by design.

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Hadronics implementation

• Distinguish process and model
• Separate model designs
• for parameterized, data and theory driven
• Data driven models Low energy neutron
• Based on evaluated data
• ENDF, Jef, JENDL, CENDL, ENSDF, etc..
• Parameterization driven models, e.g.
• High E inelastic
• Stopping particles p-, K-

59
Hadronic physics processes

• Inelastic and coherent elastic scattering
• Capture of neutral, strongly interacting
  particles by nuclei, and neutron-induced fission
• Processes at rest for long-living, stopping
  particles
• New parameterisations
• total cross-section p/n-N (0/14MeV to 20GeV),
• differential cross-section p-p (0.1MeV to 3GeV)
• Neutron transport (ENDF/B-VI)
• High Energy extensions
• using techniques from heavy ion generators, and
• cascade pre-equilibrium evaporation
• Many other small improvements

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GEANT4 Physics Processes Design

• Make transparent how physics results are
  produced.
• exploiting Object-Oriented Technology
• The way cross sections are calculated
• via formulas, data files, etc. and using
  different
• data-sets (with applicability by particle,
  energy, material)
• is clearly exposed via OO design and
  separated from the way they are accessed and used
  in the algorithms.
• The way the final state is computed
• is separated from the tracking and
• is split into alternative or complementary
  models, according to
• the energy range, the particle type, the
  material.
• Multiple implementations of physics processes and
  models are available.

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Units, data libraries

• No numbers are hard-coded in formulas and
  algorithms. Instead variables and constants are
  used.
• An extensive set of units is defined in GEANT4
  and all the numerical quantities are expressed
  through units explicitly. Users are free to
  choose any units.
• Data libraries and evaluations
• ENDF/B, JENDL, FENDL, CENDL, ENSDF,JEF, BROND,
  EFF
• MENDL, IRDF, SAID, EPDL, EEDL, EADL, SANDIA,
  .....
• Distribution centers
• NEA (also for HERMES-KFA), LLNL, BNL, KEK,
• IAEA, IHEP, Helsinki, TRIUMF, FNAL (for
  MARS)........

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Electro-Magnetic physics

• Gammas
• Gamma-conversion, Compton scattering,
  Photo-electric effect
• Leptons(e, mu) charged particles(hadrons,
  ions)
• Ionisation, Bremstrahlung, Energy loss, Multiple
  scattering, transition radiation, Synchrotron
  radiation, PAI model energy loss
• Photons
• Cerenkov, Rayleigh, Reflection, Refraction,
  Absorption, Scintillation
• High energy muons and lepton-hadron interactions
• Implementation of physics to 1 KeV
• in development version

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Secondaries Produced or Not

• Lead, CO2, Lead, CO2

• Range lt safety
• Secondaries will not leave Pb not produced
• Range gt safety
• Secondaries
• leave Pb produced

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Induced fission U235, 10 MeV neutrons
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Capture by U238 of neutrons
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Isotope Production

• Isotopes produced by neutrons on Lead 208

• Small dots evaluated data
• Circles with error bars Geant
• latest model
• is in currrent release Geant4 1.0

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Visualization

• The most-used functionality is implemented
• Several drivers
• OpenGL, VRML, Open Inventor, Opacs, DAWN renderer
  (G4)
• Also choice of User Interfaces
• Terminal (text) or
• GUI Momo (G4), OPACS

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Examples and Documentation

• Six examples
• simple detectors
• different experiment types
• demonstrate essential capabilities
• Documentation
• Getting started installation guide
• User guide for application toolkit developer
• Software physics reference manuals
• G4 URL http//wwwinfo.cern.ch/asd/geant/geant4.ht
  ml

70
Applications for Geant4 Low-Energy EM Extension

• Mineralogical surveys of asteroids and moons by
  induced X-ray emission
• Analysis of background effects in X- and g-ray
  astrophysical observatories
• Neutrino experiments
• Medical applications Hadron treatment
  (secondaries)
• DNA and cellular studies

ESA Space Environment Effects Analysis Section
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Standard Radiation Environment Monitor (SREM)
Aluminium
Tantalum
Silicon (detectors)
e-
Trade-off- Performance- Cost- Mass-
Volume
e-
(p)
D1
D2
Optimised Al-Ta Sandwich structure.
Simulation outcome modularity (D3)
- Electrons gt 0.5 MeV- Protons gt 10 MeV- Heavy
ions qualitatively
Geant4 CAD-tool interface
ESA Space Environment Effects Analysis Section
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Radioactive Decay Processes and Data

• Objectives
• Allow simulation by GEANT4 of
• Nuclear radioactive decay, i.e. ?, ?-, ?,
  electron capture (EC), and isomeric transition
  (IT) or long-lived meta-stable states, the
  latter through the existing photo-evaporation
  code
• Neutron decay (?- emission).
• Simulation to be applicable to
• nuclei at rest or in motion
• nuclei specified explicitly as primary particles
  or the product of nuclear interactions

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Radioactive decay Functionality

• All nuclear/neutron decay products to be
  submitted back to the tracking process, including
• daughter nucleus (tracking interactions and
  radioactive decay through multiple generations)
• ?-rays from prompt de-excitation
• ? anti-?
• details of the atomic excitation state (EM atomic
  relaxation model)
• Need to control the scope of the simulation
• range of nuclei for which process is applicable
• volumes for which process is applicable

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Radioactive decay Current Status

• Note on theory behind of variance reduction
• G4Ion and G4IonTable modified to permit adequate
  description of nuclear and atomic state (Hisaya
  Kurashige)
• Analogue Monte Carlo decay mostly implemented,
  with all decay modes possible
• G4RadioactiveDecayMessenger allows restriction of
  range of radionuclei
• Radioactivity database for the moment contains
  just a few example nuclei (for the purposes of
  testing)

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Experiences with Geant4

• Production release in use
• used, got feedback
• from 5 experiments
• first results confirm some of G4s strengths
• in EM physics, geometry, hadronic physics
• First EM physics benchmarks
• Geant4 gives better physics _at_ same speed
• Geant4 gives better speed for same physics