Geant4 - a simulation toolkit -

Geant4Geant4- a simulation toolkit -- a simulation toolkit -

Makoto Asai (SLAC Computing Services)Makoto Asai (SLAC Computing Services)

On behalf of the Geant4 CollaborationOn behalf of the Geant4 Collaboration

December 1December 1stst, 2003 , 2003

ACAT03 @ KEKACAT03 @ KEK

http://www-unix.oit.umass.edu/~blaylock/hepex/sm-text-logo.gif

Geant4 : a simulation toolkit - M.Asai (SLAC) - Dec 01, 2003 @ACAT03Geant4 : a simulation toolkit - M.Asai (SLAC) - Dec 01, 2003 @ACAT03 22

ContentsContents General introduction and brief historyGeneral introduction and brief history

Geant4 kernelGeant4 kernel

GeometryGeometry

PhysicsPhysics

Highlights of the new developmentsHighlights of the new developments

Highlights of user applications Highlights of user applications

User support processesUser support processes

SummarySummary

General introduction General introduction and brief historyand brief history


What is Geant4?What is Geant4? Geant4 is an object-oriented toolkit for simulation of Geant4 is an object-oriented toolkit for simulation of

elementary particles passing through and interacting with elementary particles passing through and interacting with

matter. It includes a complete range of functionality including matter. It includes a complete range of functionality including

tracking, geometry, physics models and hits. tracking, geometry, physics models and hits.

Geant4's application area includes high energy and nuclear Geant4's application area includes high energy and nuclear

physics experiments, accelerator and shielding studies, space physics experiments, accelerator and shielding studies, space

engineering, medical physics and several other fields. engineering, medical physics and several other fields.

Geant4 is the successor of GEANT3, the world-standard toolkit Geant4 is the successor of GEANT3, the world-standard toolkit

for HEP detector simulation. Geant4 is one of the first for HEP detector simulation. Geant4 is one of the first

successful attempt to re-design a major package of HEP successful attempt to re-design a major package of HEP

software for the next generation of experiments using an software for the next generation of experiments using an

Object-Oriented environment. Object-Oriented environment.


Flexibility of Geant4Flexibility of Geant4 In order to meet wide variety of requirements from various In order to meet wide variety of requirements from various

application fields, a large degree of functionality and flexibility application fields, a large degree of functionality and flexibility

are provided. are provided.

Geant4 has many types of geometrical descriptions to describe Geant4 has many types of geometrical descriptions to describe

most complicated and realistic geometries most complicated and realistic geometries

CSG, BREP, BooleanCSG, BREP, Boolean

XML interfaceXML interface

The physics processes offered cover a comprehensive range The physics processes offered cover a comprehensive range

including electromagnetic, hadronic and optical processes for a including electromagnetic, hadronic and optical processes for a

large set of long-lived particles in materials and elements, over large set of long-lived particles in materials and elements, over

a wide energy range. The applicable energy range begins, in a wide energy range. The applicable energy range begins, in

some cases, from 100 eV and extends up to the TeV energy some cases, from 100 eV and extends up to the TeV energy

range. range.


Physics in Geant4Physics in Geant4 It is rather unrealistic to develop a uniform physics model to It is rather unrealistic to develop a uniform physics model to

cover wide variety of particles and/or wide energy range.cover wide variety of particles and/or wide energy range. Much wider coverage of physics comes from mixture of theory-Much wider coverage of physics comes from mixture of theory-

driven, parameterized, and empirical formulae. Thanks to driven, parameterized, and empirical formulae. Thanks to polymorphism mechanism, both cross-sections and models polymorphism mechanism, both cross-sections and models (final state generation) can be combined in arbitrary manners (final state generation) can be combined in arbitrary manners into one particular process.into one particular process. Standard EM processesStandard EM processes Low energy EM processesLow energy EM processes Hadronic processesHadronic processes Photon/lepton-hadron processesPhoton/lepton-hadron processes Optical photon processesOptical photon processes Decay processesDecay processes Shower parameterizationShower parameterization Event biasing technique Event biasing technique


Geant4 – Its history and futureGeant4 – Its history and future Dec ’94 - Project startDec ’94 - Project start

Apr ’97 - First alpha release Apr ’97 - First alpha release

Jul ’98 - First beta release Jul ’98 - First beta release

Dec ’98 - Geant4 0.0 (first public) releaseDec ’98 - Geant4 0.0 (first public) release

Jul ’99 - Geant4 0.1 releaseJul ’99 - Geant4 0.1 release

……

Jun ’03 - Geant4 5.2 releaseJun ’03 - Geant4 5.2 release

Dec 12Dec 12thth, ’03 - Geant4 6.0 release (planned), ’03 - Geant4 6.0 release (planned)

We currently provide two to three public releases and We currently provide two to three public releases and

bimonthly beta releases in between public releases every bimonthly beta releases in between public releases every

year.year.


Geant4 Geant4 CollaborationCollaboration

Collaborators also from non-member institutions, including

Budker Inst. of PhysicsIHEP Protvino

MEPHI Moscow Pittsburg University

Helsinki Inst. Ph.

PPARCUniv. Barcelona

HARP

Lebedev

Geant4 kernelGeant4 kernel


Geant4 kernelGeant4 kernel Geant4 consists of 17 categories.Geant4 consists of 17 categories.

Independently developed and Independently developed and

maintained by WG(s) responsible maintained by WG(s) responsible

to each category.to each category.

Interfaces between categories Interfaces between categories

(e.g. top level design) are (e.g. top level design) are

maintained by the global maintained by the global

architecture WG.architecture WG.

Geant4 KernelGeant4 Kernel

Handles run, event, track, step, Handles run, event, track, step,

hit, trajectory.hit, trajectory.

Provides frameworks of Provides frameworks of

geometrical representation and geometrical representation and

physics processes.physics processes.

Geant4

ReadoutVisuali zation

Persis tency

Run

Event

Inter faces

Tracking

Digits + Hits

Processes

Track

Geometry Particle

Graphic _reps

Material

Intercoms

Global


Tracking and processesTracking and processes Geant4 tracking is general. Geant4 tracking is general.

It is independent to It is independent to

the particle type the particle type

the physics processes involving to a particlethe physics processes involving to a particle

It gives the chance to all processes It gives the chance to all processes

To contribute to determining the step lengthTo contribute to determining the step length

To contribute any possible changes in physical To contribute any possible changes in physical

quantities of the trackquantities of the track

To generate secondary particlesTo generate secondary particles

To suggest changes in the state of the trackTo suggest changes in the state of the track

e.g. to suspend, postpone or kill it.e.g. to suspend, postpone or kill it.


Processes in Geant4Processes in Geant4 In Geant4, particle transportation is a process as well, by which In Geant4, particle transportation is a process as well, by which

a particle interacts with geometrical volume boundaries and a particle interacts with geometrical volume boundaries and

field of any kind.field of any kind.

Because of this, for example, shower parameterization Because of this, for example, shower parameterization

process can take over from the ordinary transportation process can take over from the ordinary transportation

without modifying the transportation process.without modifying the transportation process.

Each particle has its own list of applicable processes. At each Each particle has its own list of applicable processes. At each

step, all processes listed are invoked to get proposed physical step, all processes listed are invoked to get proposed physical

interaction lengths.interaction lengths.

The process which requires the shortest interaction length (in The process which requires the shortest interaction length (in

space-time) limits the step. space-time) limits the step.


CutsCuts in Geant4 in Geant4 A Cut in Geant4 is a A Cut in Geant4 is a production thresholdproduction threshold..

Only for physics processes that have infrared divergenceOnly for physics processes that have infrared divergence Not tracking cut, which does not exist in Geant4Not tracking cut, which does not exist in Geant4

Energy threshold must be determined at which discreteEnergy threshold must be determined at which discrete energy energy loss is replaced by continuous lossloss is replaced by continuous loss Old way: Old way:

Track primary particle until cut-off energy is reached,Track primary particle until cut-off energy is reached, calculate continuous loss and dump it at that point,calculate continuous loss and dump it at that point, stop stop tracking primarytracking primary

Create secondaries only above cut-off energy, or add to Create secondaries only above cut-off energy, or add to continuous loss of primary for less energetic secondariescontinuous loss of primary for less energetic secondaries

Geant4 way: Geant4 way: Specify range (which is converted toSpecify range (which is converted to energy for each energy for each

material) at which continuous loss begins, trackmaterial) at which continuous loss begins, track primary primary particle one more step to make it down to zero rangeparticle one more step to make it down to zero range

Create secondaries only above specified range, or add to Create secondaries only above specified range, or add to continuous loss of primary for less energetic secondariescontinuous loss of primary for less energetic secondaries


Energy cut vs. range cutEnergy cut vs. range cut 500 MeV/c proton in liq.Ar (4mm) / Pb (4mm) sampling calorimeter500 MeV/c proton in liq.Ar (4mm) / Pb (4mm) sampling calorimeter

liq.Ar

Pb liq.Ar

Pb

Geant3 (energy cut)Geant3 (energy cut) Ecut = 450 keVEcut = 450 keV

Geant4 (range cut)Geant4 (range cut) Rcut = 1.5 mmRcut = 1.5 mm Corresponds to Corresponds to

Ecut in liq.Ar = 450 keV, Ecut in liq.Ar = 450 keV, Ecut in Pb = 2 MeVEcut in Pb = 2 MeV

GeometryGeometry


VolumeVolume Three conceptual layers Three conceptual layers

G4VSolid -- G4VSolid -- shape, sizeshape, size G4LogicalVolume -- G4LogicalVolume -- daughter physical volumes, daughter physical volumes,

material, sensitivity, user limits, etc.material, sensitivity, user limits, etc. G4VPhysicalVolume -- G4VPhysicalVolume -- position, rotationposition, rotation

Hierarchal three layers of geometry description allows maximum Hierarchal three layers of geometry description allows maximum reuse of information to minimize the use of memory space.reuse of information to minimize the use of memory space.

G4Box

G4Tubs

G4VSolid G4VPhysicalVolume

G4Material

G4VSensitiveDetector

G4PVPlacement

G4PVParameterised

G4VisAttributes

G4LogicalVolume


SolidSolid Geant4 geometry module supports variety of Geant4 geometry module supports variety of

representations of shapes.representations of shapes. CSG (Constructed Solid Geometry) solidsCSG (Constructed Solid Geometry) solids

G4Box, G4Tubs, G4Cons, G4Trd, …G4Box, G4Tubs, G4Cons, G4Trd, … Analogous to simple GEANT3 CSG Analogous to simple GEANT3 CSG

solidssolids Specific solids (CSG like)Specific solids (CSG like)

G4Polycone, G4Polyhedra, G4Hype, …G4Polycone, G4Polyhedra, G4Hype, … BREP (Boundary REPresented) solidsBREP (Boundary REPresented) solids

G4BREPSolidPolycone, G4BREPSolidPolycone, G4BSplineSurface, …G4BSplineSurface, …

Any order surfaceAny order surface Boolean solidsBoolean solids

G4UnionSolid, G4SubtractionSolid, …G4UnionSolid, G4SubtractionSolid, …


Physical volumePhysical volume G4PVPlacement 1 Placement = One VolumeG4PVPlacement 1 Placement = One Volume

A volume instance positioned once in its mother volumeA volume instance positioned once in its mother volume G4PVParameterised 1 Parameterized = Many VolumesG4PVParameterised 1 Parameterized = Many Volumes

Parameterized by the copy numberParameterized by the copy number Shape, size, material, position and rotation can be Shape, size, material, position and rotation can be

parameterized, by implementing a concrete class of parameterized, by implementing a concrete class of G4VPVParameterisationG4VPVParameterisation..

Reduction of memory consumption Reduction of memory consumption G4PVReplica 1 Replica = Many VolumesG4PVReplica 1 Replica = Many Volumes

Slicing a volume into smaller pieces (if it has a symmetry)Slicing a volume into smaller pieces (if it has a symmetry) G4ReflectionFactory 1 Placement = a set of VolumesG4ReflectionFactory 1 Placement = a set of Volumes

Generating a pair of placements of a volume and its reflected Generating a pair of placements of a volume and its reflected volumevolume

Useful typically for end-cap calorimeterUseful typically for end-cap calorimeter G4AssemblyVolume 1 Placement = a set of PlacementsG4AssemblyVolume 1 Placement = a set of Placements

Position a group of volumesPosition a group of volumes


Smart voxelizationSmart voxelization In case of Geant 3.21, the user had to carefully implement his/her In case of Geant 3.21, the user had to carefully implement his/her

geometry to maximize the performance of geometrical navigation.geometry to maximize the performance of geometrical navigation. While in Geant4, user’s geometry is automatically optimized to most While in Geant4, user’s geometry is automatically optimized to most

suitable to the navigation. - "Voxelization"suitable to the navigation. - "Voxelization" For each mother volume, one-dimensional virtual division is performed.For each mother volume, one-dimensional virtual division is performed. Subdivisions (slices) containing same volumes are gathered into one.Subdivisions (slices) containing same volumes are gathered into one. Additional division again using second and/or third Cartesian axes, if Additional division again using second and/or third Cartesian axes, if

needed.needed. "Smart voxels""Smart voxels" are computed at initialisation time are computed at initialisation time

When the detector geometry is When the detector geometry is closedclosed Does not require large memory or computing resourcesDoes not require large memory or computing resources At tracking time, searching is done in a hierarchy of virtual divisionsAt tracking time, searching is done in a hierarchy of virtual divisions


Geometry checking toolsGeometry checking tools An An overlappingoverlapping volume is a contained volume is a contained

volume which actually protrudes from its volume which actually protrudes from its mother volumemother volume Volumes are also often positioned in Volumes are also often positioned in

a same volume with the intent of not a same volume with the intent of not provoking intersections between provoking intersections between themselves. When volumes in a themselves. When volumes in a common mother actually intersect common mother actually intersect themselves are defined as themselves are defined as overlappingoverlapping

Geant4 does not allow for malformed Geant4 does not allow for malformed geometriesgeometries

The problem of detecting overlaps The problem of detecting overlaps between volumes is bounded by the between volumes is bounded by the complexity of the solid models complexity of the solid models descriptiondescription

Utilities are provided for detecting wrong Utilities are provided for detecting wrong positioningpositioning Graphical toolsGraphical tools Kernel run-time commandsKernel run-time commands

PhysicsPhysics


Physics processes in Geant4Physics processes in Geant4 Each process can act at any of three space-time intervalsEach process can act at any of three space-time intervals

In time - At rest (e.g. decay at rest)In time - At rest (e.g. decay at rest) Continuously along a step (e.g. Cherenkov radiation)Continuously along a step (e.g. Cherenkov radiation) At a point - at the end of the step (e.g. decay in flight)At a point - at the end of the step (e.g. decay in flight)

““Along step actions” are applied cumulatively, while others are Along step actions” are applied cumulatively, while others are selectively applied.selectively applied.

A process can have more than one types of action according to its A process can have more than one types of action according to its nature.nature. For example, Ionization process has Along and End step For example, Ionization process has Along and End step

actionsactions Tracking handles each type of action in turn. Tracking handles each type of action in turn.

It loops over all processes with such a type of action.It loops over all processes with such a type of action. The motivation for creating these categories of actions is to keep The motivation for creating these categories of actions is to keep

the tracking independent of the physics processes.the tracking independent of the physics processes. All seven combinations of actions are possible.All seven combinations of actions are possible.

The traditional Continuous, Continuous-Discrete, Discrete and The traditional Continuous, Continuous-Discrete, Discrete and AtRest are found in these cases.AtRest are found in these cases.

The ordering of processes is important in some cases.The ordering of processes is important in some cases. e.g. Multiple scattering affects the step length.e.g. Multiple scattering affects the step length.


Electromagnetic processesElectromagnetic processes Gammas : Gammas :

Gamma-conversion, Compton scattering, Photo-electric Gamma-conversion, Compton scattering, Photo-electric effecteffect

Leptons (e, Leptons (e, ), charged hadrons, ions :), charged hadrons, ions : Energy loss (Ionisation, Bremstrahlung) or PAI model Energy loss (Ionisation, Bremstrahlung) or PAI model

energy loss, Multiple scattering, Transition radiation, energy loss, Multiple scattering, Transition radiation, Synchrotron radiation, Synchrotron radiation,

Optical photons : Optical photons : Cerenkov, Rayleigh, Reflection, Refraction, Absorption, Cerenkov, Rayleigh, Reflection, Refraction, Absorption,

ScintillationScintillation High energy High energy Alternative implementation Alternative implementation

Standard EM package ignores the binding energy of Standard EM package ignores the binding energy of electron to an atom, while Low Energy EM package takes it electron to an atom, while Low Energy EM package takes it into account.into account.

‘‘Standard’ for applications that do not need to go below 1 Standard’ for applications that do not need to go below 1 KeVKeV

‘‘Low Energy’: down to 250eV (e+/Low Energy’: down to 250eV (e+/), O(0.1), O(0.1m) for hadronsm) for hadrons


Multiple Multiple scatterinscatterin

gg

Angle (deg)

Examples of Examples of comparisons:comparisons:

15.7 MeV e- 15.7 MeV e-

on gold foil on gold foil

Modelling & Modelling & comparisons:comparisons:

L. UrbanL. Urban


Hadronic and Photolepton-Hadronic and Photolepton-hadron processeshadron processes

Each hadronic process may have one or more cross section Each hadronic process may have one or more cross section

data sets, and final state production models associated with it. data sets, and final state production models associated with it.

Each one has its own energy range of applicability.Each one has its own energy range of applicability.

The term “data set” is meant in a broad sense to be an The term “data set” is meant in a broad sense to be an

object that encapsulates methods and data for object that encapsulates methods and data for

calculating total cross sections.calculating total cross sections.

The term “model” is meant in a broad sense to be an The term “model” is meant in a broad sense to be an

object that encapsulates methods and data for object that encapsulates methods and data for

calculating final state products.calculating final state products.


Parameterization and data driven Parameterization and data driven modelsmodels

Parameterization models on the flyParameterization models on the fly high energy inelastic (Aachen, CERN)high energy inelastic (Aachen, CERN) low energy inelastic, elastic, fission, capture (TRIUMF, UBC, CERN, low energy inelastic, elastic, fission, capture (TRIUMF, UBC, CERN,

SLAC)SLAC) Parameterization models for stopping particlesParameterization models for stopping particles

base line (TRIUMF, CHAOS)base line (TRIUMF, CHAOS) mu- (TRIUMF, FIDUNA)mu- (TRIUMF, FIDUNA) pi- (INFN, CERN, TRIUMF) pi- (INFN, CERN, TRIUMF) K- (Crystal Barrel, TRIUMF)K- (Crystal Barrel, TRIUMF) anti-protons (JLAB, CERN)anti-protons (JLAB, CERN) Electromagnetic transitions of the exotic atom prior to capture; Electromagnetic transitions of the exotic atom prior to capture;

effects of atomic binding. (Novosibirsk, ESA)effects of atomic binding. (Novosibirsk, ESA) Data driven modelsData driven models

Low energy neutron transport (neutron_hp),Low energy neutron transport (neutron_hp), Radioactive decay (DERA, ESA)Radioactive decay (DERA, ESA) photon evaporation (INFN)photon evaporation (INFN) elastic scattering (TRIUMF, U.Alberta, CERN)elastic scattering (TRIUMF, U.Alberta, CERN) internal conversion (ESA) internal conversion (ESA) etc..etc..


Theory driven modelsTheory driven models Ultra-high energy modelsUltra-high energy models

Parton transport model (U.Frankfurt, in discussion)Parton transport model (U.Frankfurt, in discussion) High energy modelsHigh energy models

‘‘Fritjof’ type string model (CERN)Fritjof’ type string model (CERN) Quark gluon String model (CERN)Quark gluon String model (CERN) Pythia(7) interface (Lund, CERN)Pythia(7) interface (Lund, CERN)

Intra-nuclear transport models (or replacements)Intra-nuclear transport models (or replacements) Hadronic cascade+pre-equilibrium model (HIP, CERN)Hadronic cascade+pre-equilibrium model (HIP, CERN) Binary and Bertini cascade models (HIP, CERN, Novosibirsk, Binary and Bertini cascade models (HIP, CERN, Novosibirsk,

SLAC)SLAC) QMD type models (CERN, Inst.Th.Phys. Frankfurt)QMD type models (CERN, Inst.Th.Phys. Frankfurt) Chiral invariant phase-space decay model (JLAB, CERN, ITEP)Chiral invariant phase-space decay model (JLAB, CERN, ITEP) Partial Mars rewrite (Kyoto, Uvic, in collaboration with FNAL)Partial Mars rewrite (Kyoto, Uvic, in collaboration with FNAL)

De-excitationDe-excitation Evaporation, fission, multi-fragmentation, fermi-break-up (CMS)Evaporation, fission, multi-fragmentation, fermi-break-up (CMS)


Hadronic Model InventoryHadronic Model Inventory

1 MeV 10 MeV 100 MeV 1 GeV 10 GeV 100 GeV 1 TeV

LEP

HEP ( up to 20 TeV)

Photon EvapMultifragmentFermi breakup

Fission

Evaporation

Pre-compound Bertini cascade

Binary cascade

QG String (up to 100 TeV)

MARS

FTF String (up to 20 TeV)

High precision neutron

At rest Absorption

K, anti-p Photo-nuclear, electro-nuclear

CHIPS (gamma)

CHIPS

LE pp, pn

Rad. decay


VerificationVerification The verification effort of the geant4 hadronic working group is The verification effort of the geant4 hadronic working group is

grouped into several sections:grouped into several sections: Inclusive cross-sectionsInclusive cross-sections Thin target comparisonsThin target comparisons Verification of model componentsVerification of model components Code comparisons (least effective)Code comparisons (least effective) Complete application testsComplete application tests Robustness.Robustness.

A few examples of each are given in the following slides.A few examples of each are given in the following slides.


Proton reaction Proton reaction total total

cross-section: cross-section:

J.P.Wellisch


Pion production examples, QGS:Pion production examples, QGS:Rapidity distributions and invariant Rapidity distributions and invariant

cross-section predictions in quark gluon string cross-section predictions in quark gluon string modelmodel

100 GeV pi+ on Gold

400GeV protons on Lithium


Forward peaks in proton Forward peaks in proton induced neutron induced neutron

productionproduction

Beryllium

Aluminum

Iron

Lead

256 MeV dataNeutrons at 7.5deg.


Production from 730 MeV p Production from 730 MeV p (Bertini Model)(Bertini Model)


Low energy neutron capture:Low energy neutron capture:gammas from 14 MeV capture on gammas from 14 MeV capture on

UraniumUranium


Nuclear interactions with Geant4 Nuclear interactions with Geant4 versus experimentversus experiment

Phantom and experimental results from H.Paganetti, B.Gottschalk, Medical physics Vol. 30, No.7, 2003

10-9 p

C/i

ncid

ent p

roto

n

Channel


Atlas HEC (e/Atlas HEC (e/ ratio) ratio)


CMS ECAL + HCAL testbeamCMS ECAL + HCAL testbeam GEANT3 - GEANT4 comparison GEANT3 - GEANT4 comparison

100 GeV pi+ ECAL+HCAL


"Educated guess" physics lists"Educated guess" physics lists In Geant4, the physics lists serve the same purpose as the In Geant4, the physics lists serve the same purpose as the

"packages" (GHEISHA, FLUKA, GCALOR) in geant3."packages" (GHEISHA, FLUKA, GCALOR) in geant3. Conceptually, the two are identical.Conceptually, the two are identical. Both ways provide the physics and its modeling to an application.Both ways provide the physics and its modeling to an application. Each "package" is built of a complete and consistent set of Each "package" is built of a complete and consistent set of

modelsmodels In Geant4, the number of "packages" is quite large. Each option In Geant4, the number of "packages" is quite large. Each option

comes with trade-offs in descriptive power and performance.comes with trade-offs in descriptive power and performance. It simply became clear that writing a good physics list is not trivial, in It simply became clear that writing a good physics list is not trivial, in

particular when hadronic physics is involved.particular when hadronic physics is involved. It is nice to be able to exploit the full power in the flexibility and It is nice to be able to exploit the full power in the flexibility and

variety of hadronic physics modeling in geant4, but being forced variety of hadronic physics modeling in geant4, but being forced to do so is not what we want.to do so is not what we want.

It is also nice to have the physics transparently in front of the It is also nice to have the physics transparently in front of the user and to exploit it in the best possible way, but being forced to user and to exploit it in the best possible way, but being forced to understand everything is (very understandably) not what people understand everything is (very understandably) not what people want, either.want, either.

We have systematically accumulated experience with various We have systematically accumulated experience with various combinations of cross-section and models over the past years. Today combinations of cross-section and models over the past years. Today we provide a set of physics lists institutionalizing this knowledge.we provide a set of physics lists institutionalizing this knowledge. "Educated guess" physics lists"Educated guess" physics lists


Use-case driven packagesUse-case driven packages LCG simulation project.LCG simulation project. HEP calorimetry. HEP calorimetry. HEP trackers. HEP trackers. 'Average' collider detector 'Average' collider detector Low energy dosimetric Low energy dosimetric

applications with neutrons applications with neutrons low energy nucleon low energy nucleon

penetration shielding penetration shielding linear collider neutron fluxeslinear collider neutron fluxes high energy penetration high energy penetration

shieldingshielding medical and other life-saving medical and other life-saving

neutron applicationsneutron applications low energy dosimetric low energy dosimetric

applications applications

high energy production high energy production targetstargets

e.g. 400GeV protons on C or e.g. 400GeV protons on C or BeBe

medium energy production medium energy production targetstargets

e.g. 15-50 GeV p on light e.g. 15-50 GeV p on light targetstargets

LHC neutron fluxes LHC neutron fluxes low background experimentslow background experiments Air shower applications (still Air shower applications (still

working on this)working on this)

Each package has several Each package has several physics lists suitable to the physics lists suitable to the use-caseuse-case


DecayDecay A decay table is associated to the definition of each particle type.A decay table is associated to the definition of each particle type.

A track can have a decay channel. If it has, it exactly decays A track can have a decay channel. If it has, it exactly decays

through this channel without randomizing by the decay ratio.through this channel without randomizing by the decay ratio.

This allows the user to import decay chains generated by This allows the user to import decay chains generated by

physics generators such as Pythia, and rely on Geant4 physics generators such as Pythia, and rely on Geant4

tracking for such unstable particles.tracking for such unstable particles.

Primary particle list

B0

K0L…

B0 G4Track

K0L…

“pre-defined”decay channel


Optical processesOptical processes Geant4 has a particle named “Optical Photon”, which is Geant4 has a particle named “Optical Photon”, which is

distinguished from gamma. It interacts by optical processes.distinguished from gamma. It interacts by optical processes. Geant4 is an ideal framework for modeling the optics of Geant4 is an ideal framework for modeling the optics of

scintillation and Cerenkov detectors and their associated light scintillation and Cerenkov detectors and their associated light

guides. This is founded in the toolkit's unique capability of guides. This is founded in the toolkit's unique capability of

commencing the simulation with the propagation of a charged commencing the simulation with the propagation of a charged

particle and completing it with the detection of the ensuing particle and completing it with the detection of the ensuing

optical photons on photo sensitive areas, all within the same optical photons on photo sensitive areas, all within the same

event loop. event loop. This functionality is now employed world-wide in experimental This functionality is now employed world-wide in experimental

simulations as diverse as ALICE, ANTARES, AMANDA, Borexino, simulations as diverse as ALICE, ANTARES, AMANDA, Borexino,

Icarus, LHCb, HARP, KOPIO, the Pierre Auger Observatory, and Icarus, LHCb, HARP, KOPIO, the Pierre Auger Observatory, and

the GATE (Imaging in Nuclear Medicine) Collaboration. the GATE (Imaging in Nuclear Medicine) Collaboration.


Optical processesOptical processes Optical photons are generated if one or more of following Optical photons are generated if one or more of following

processes are activated.processes are activated. Cerenkov radiation, Cerenkov radiation, Transition radiation, Transition radiation, ScintillationScintillation

Optical processes built in Geant4Optical processes built in Geant4 Absorption, Absorption, Rayleigh scatteringRayleigh scattering Boundary Processes (reflection, refraction)Boundary Processes (reflection, refraction)

Optical properties, e.g. dielectric coefficient and surface Optical properties, e.g. dielectric coefficient and surface

smoothness, can be set to a volume.smoothness, can be set to a volume.


Shower parameterization Shower parameterization frameworkframework

Geant4 includes a built-in framework for shower Geant4 includes a built-in framework for shower

parameterization scheme. Currently, the user has to concrete parameterization scheme. Currently, the user has to concrete

his/her own parameterization assigned to a logical volume, his/her own parameterization assigned to a logical volume,

which is then called as an “envelop”.which is then called as an “envelop”. Regardless of the existence of granular daughter geometry, Regardless of the existence of granular daughter geometry,

a particle comes into the envelop can be fully treated by a particle comes into the envelop can be fully treated by

the shower parameterization process. the shower parameterization process. The user still have a dynamic choice to take his/her The user still have a dynamic choice to take his/her

parameterization or to follow the ordinary tracking in the parameterization or to follow the ordinary tracking in the

granular geometry.granular geometry. The shower parameterization process can directly contact The shower parameterization process can directly contact

to a sensitive detector associating to the volume to to a sensitive detector associating to the volume to

produce more than one distributed hits.produce more than one distributed hits.

Highlights ofHighlights ofnew developmentsnew developments


Event biasing in Geant4Event biasing in Geant4 Event biasing (variance reduction) technique is one of the most Event biasing (variance reduction) technique is one of the most

important requirements, which Geant4 collaboration is aware important requirements, which Geant4 collaboration is aware

of.of. This feature could be utilized by many application fields such as This feature could be utilized by many application fields such as

Radiation shieldingRadiation shielding DosimetryDosimetry

Since Geant4 is a toolkit and also all source code is open, the Since Geant4 is a toolkit and also all source code is open, the

user can do whatever he/she wants.user can do whatever he/she wants. CMS, ESA, Alice, and some other experiments have already CMS, ESA, Alice, and some other experiments have already

had their own implementations of event biasing options.had their own implementations of event biasing options. It’s much better and convenient for the user if Geant4 itself It’s much better and convenient for the user if Geant4 itself

provides most commonly used event biasing techniques.provides most commonly used event biasing techniques.


Current features in Geant4Current features in Geant4 Partial MARS migration Partial MARS migration

n, p, pi, K (< 5 GeV)n, p, pi, K (< 5 GeV) Since Geant4 0.0Since Geant4 0.0

General particle source moduleGeneral particle source module Primary particle biasingPrimary particle biasing Since Geant4 3.0Since Geant4 3.0

Radioactive decay moduleRadioactive decay module Physics process biasing in terms of decay products and Physics process biasing in terms of decay products and

momentum distributionmomentum distribution Since Geant4 3.0Since Geant4 3.0

Cross-section biasing (partial) for hadronic physics Cross-section biasing (partial) for hadronic physics Since Geant4 3.0Since Geant4 3.0

Leading particle biasingLeading particle biasing Since Geant4 4.0Since Geant4 4.0

Geometry based biasingGeometry based biasing Weight associating with real volume or artificial volumeWeight associating with real volume or artificial volume Since Geant4 5.0Since Geant4 5.0


Geometrical importance Geometrical importance biasingbiasing

Define importance for each Define importance for each geometrical regiongeometrical region

Duplicate a track with half (or Duplicate a track with half (or relative) weight if it goes relative) weight if it goes toward more important region.toward more important region.

Russian-roulette in another Russian-roulette in another direction.direction.

Scoring particle flux with Scoring particle flux with weightsweights At the surface of volumesAt the surface of volumes

I = 1.0 I = 2.0

W=1.0W=0.5W=0.5

P = 0.5


Cuts per RegionCuts per Region Geant4 has had a unique and uniform production threshold (‘cut’) Geant4 has had a unique and uniform production threshold (‘cut’)

expressed in length (range of secondary).expressed in length (range of secondary). For all volumesFor all volumes One cut in range for each particleOne cut in range for each particle

By default is the same cut for all particlesBy default is the same cut for all particles.. Consistency of the physics simulatedConsistency of the physics simulated

A volume with dense material will not dominate the A volume with dense material will not dominate the simulation time at the expense of sensitive volumes with simulation time at the expense of sensitive volumes with light material.light material.

Yet appropriate length scales can vary greatly between different Yet appropriate length scales can vary greatly between different areas of a large detectorareas of a large detector E.g. a vertex detector (5 E.g. a vertex detector (5 m) and a muon detector (2.5 cm).m) and a muon detector (2.5 cm). Having a unique (low) cut can create a performance penalty.Having a unique (low) cut can create a performance penalty.

Requests from ATLAS, BABAR, CMS, LHCb, …, to allow several cutsRequests from ATLAS, BABAR, CMS, LHCb, …, to allow several cuts Enabling the tuning of production thresholds at the level of a Enabling the tuning of production thresholds at the level of a

sub-detector, i.e. sub-detector, i.e. regionregion.. Cuts are applied only for gamma, electron and positron.Cuts are applied only for gamma, electron and positron.

‘‘Full release’ in Geant4 5.1 (end April, 2003)Full release’ in Geant4 5.1 (end April, 2003) Comparable run-time performance compared to global cuts.Comparable run-time performance compared to global cuts.


RegionRegion Introducing the concept of Introducing the concept of

region.region. Set of geometry volumes, Set of geometry volumes,

typically of a sub-system;typically of a sub-system; Or any group of volumes;Or any group of volumes;

A cut in range is associated to a A cut in range is associated to a

region;region; a different range cut for each a different range cut for each

particle is allowed in a region.particle is allowed in a region. Typical UsesTypical Uses

barrel + end-caps of the barrel + end-caps of the

calorimeter can be a region;calorimeter can be a region; ““Deep” areas of support Deep” areas of support

structures can be a region.structures can be a region.

Region B

RegionB

DefaultRegion Region B

Region B

Region A

CC

Highlights ofHighlights ofUsers ApplicationsUsers Applications


Geant4 in HEPGeant4 in HEP

ATLAS (CERN-LHC)ATLAS (CERN-LHC)

22 x 22 x 44 m22 x 22 x 44 m33

15,000 ton15,000 ton 　　　　　　　　

4 million channels4 million channels

40 MHz readout40 MHz readout



View of CMS muon system

Sliced view of CMS barrel detectors

View of 180 Higgs event simulated in CMS Tracker detector

CMS


A Typical event in the Testbeam

Red lines: Charged particleGreen lines : Optical Photons.

LHCb


Geant4 for beam Geant4 for beam transportationtransportation




Gamma ray astronomy from 15 keV to 10 MeV Launched 17 October 2002 Length 5 m, diameter 3.7 m, mass 4 tons

INTEGRALINTEGRAL


INTEGRAL in the ESA/ESTEC test center

INTEGRAL Geant4 model byINTEGRAL Geant4 model byUniversity of University of SouthamptonSouthampton


Space Environments Space Environments and Effects Sectionand Effects Section

International Space Station (ISS)International Space Station (ISS)


Space Radiation: Solar Events Space Radiation: Solar Events of October-November 2003!of October-November 2003!

The effects of space radiation on spacecraftand on astronauts can be simulated with Geant4

Images by the ESA/NASA SOHO spacecraft


ESA Space Environment & Effects Analysis Section

DESIREDESIRE (Dose Estimation by Simulation of the (Dose Estimation by Simulation of the ISS Radiation Environment)ISS Radiation Environment)

KTH Stockholm, ESTEC, EAC, NASA JohnsonKTH Stockholm, ESTEC, EAC, NASA Johnson Prediction of the ambient energetic particle Prediction of the ambient energetic particle

environment (environment (SPENVISSPENVIS & additional models) & additional models) Construction of COLUMBUS geometry in Construction of COLUMBUS geometry in

Geant4Geant4 Radiation transport, including secondary Radiation transport, including secondary

particle production, through the geometryparticle production, through the geometry Calculation of astronaut radiation dosesCalculation of astronaut radiation doses



User SupportUser Support


User SupportUser Support Geant4 Collaboration offers extensive user supports.Geant4 Collaboration offers extensive user supports.

DocumentsDocuments

ExamplesExamples

Users workshopsUsers workshops

Tutorial coursesTutorial courses

HyperNews and mailing listHyperNews and mailing list

Bug reporting system Bug reporting system

Requirements tracking systemRequirements tracking system

Daily “private” communicationsDaily “private” communications

New implementation - Technical ForumNew implementation - Technical Forum


Documents for usersDocuments for users One introduction and Five user manualsOne introduction and Five user manuals

http://wwwasd.web.cern.ch/wwwasd/geant4/http://wwwasd.web.cern.ch/wwwasd/geant4/G4UsersDocuments/ Overview/html/index.htmlG4UsersDocuments/ Overview/html/index.html

Installation guideInstallation guide User's guide for application developersUser's guide for application developers

For a user who develops a simulation application using For a user who develops a simulation application using Geant4 Geant4

User's guide for toolkit developersUser's guide for toolkit developers For a user who develops a module which alternates or For a user who develops a module which alternates or

enhances some of geant4 functionalities enhances some of geant4 functionalities Physics reference manualPhysics reference manual

Detailed description of each physics process with Detailed description of each physics process with information of referencesinformation of references

Software reference manualSoftware reference manual LXR source code browser maintained by TRIUMF and KEK.LXR source code browser maintained by TRIUMF and KEK. Materials of past tutorials / presentations, HyperNews and Web Materials of past tutorials / presentations, HyperNews and Web

pages maintained by developers also available via Geant4 pages maintained by developers also available via Geant4 official Web page.official Web page.

"Geant4 general paper" - NIM A 506."Geant4 general paper" - NIM A 506.


ExamplesExamples Along the code releases, Geant4 provides examples which help Along the code releases, Geant4 provides examples which help

user's understanding of functionalities of Geant4 and are user's understanding of functionalities of Geant4 and are

reusable as "skeletons" of user's application.reusable as "skeletons" of user's application.

Three levels of examplesThree levels of examples

Novice examples : Novice examples :

Demonstrate most basic featuresDemonstrate most basic features

Extended examples : Extended examples :

Highlight some functionalities / use-cases in detailHighlight some functionalities / use-cases in detail

Some examples require external package(s)Some examples require external package(s)

Advanced examples :Advanced examples :

Most realistic applicationsMost realistic applications

User's contributionsUser's contributions


Geant4 users workshopGeant4 users workshop Users workshops were held or are going to be held hosted by Users workshops were held or are going to be held hosted by

several institutes for various user communities.several institutes for various user communities.

KEK - Dec.2000, Jul.2001, Mar.2002, Jul.2002, Mar.2003, KEK - Dec.2000, Jul.2001, Mar.2002, Jul.2002, Mar.2003,

Jul.2003Jul.2003

SLAC - Feb.2002SLAC - Feb.2002

Spain (supported by INFN) - Jul.2002Spain (supported by INFN) - Jul.2002

CERN - Nov.2002CERN - Nov.2002

ESA/NASA - Jan.2003, May.2004ESA/NASA - Jan.2003, May.2004

dedicated to space-related usersdedicated to space-related users

Helsinki - Oct.2003Helsinki - Oct.2003

Local workshops of one or two days were held or are Local workshops of one or two days were held or are

planned at several places.planned at several places.


Geant4 tutorials / lecturesGeant4 tutorials / lectures In addition to the users workshops, many tutorial courses and In addition to the users workshops, many tutorial courses and

lectures with some discussion time slots were held for various lectures with some discussion time slots were held for various user communities.user communities. CERN School of ComputingCERN School of Computing Italian National School for HEP/Nuclear PhysicistsItalian National School for HEP/Nuclear Physicists MC2000, MCNEG workshop, MC2000, MCNEG workshop, IEEE NSS/MIC IEEE NSS/MIC KEK, SLAC, DESY, FNAL, INFN, Frascati, Karolinska, KEK, SLAC, DESY, FNAL, INFN, Frascati, Karolinska,

GranSasso, etc.GranSasso, etc. ATLAS, CMS, LHCbATLAS, CMS, LHCb Tutorials/lectures at universitiesTutorials/lectures at universities

U.K. - ImperialU.K. - Imperial Italy - Genoa, Bologna, Udine, Roma, TriesteItaly - Genoa, Bologna, Udine, Roma, Trieste

Near future tutorial coursesNear future tutorial courses KEK (Dec. 8KEK (Dec. 8thth-11-11thth, 2003) , 2003) Vanderbilt Univ. TN. USA (Jan. 11Vanderbilt Univ. TN. USA (Jan. 11thth-13-13thth, 2004), 2004) SLAC (Mar. 8SLAC (Mar. 8thth-10-10thth, 2004), 2004)


HyperNewsHyperNews HyperNews system was set up in April 2001 HyperNews system was set up in April 2001


HyperNewsHyperNews 19 categories 19 categories Not only “user-Not only “user-

developer”, but also developer”, but also

“user-user” “user-user”

information exchanges information exchanges

are quite intensive.are quite intensive.


HyperNews is quite activeHyperNews is quite active


Technical ForumTechnical Forum In the Technical Forum, the Geant4 Collaboration, its user In the Technical Forum, the Geant4 Collaboration, its user

community and resource providers discuss:community and resource providers discuss: major user and developer requirements, user and developer major user and developer requirements, user and developer

priorities, software implementation issues, prioritized plans, priorities, software implementation issues, prioritized plans, physics validation issues, user support issuesphysics validation issues, user support issues

The Technical Forum is open to all interested parties The Technical Forum is open to all interested parties To be held at least 4 times per year (in at least two locales)To be held at least 4 times per year (in at least two locales)

The purpose of the forum is to:The purpose of the forum is to: Achieve, as much as possible, a mutual understanding of the Achieve, as much as possible, a mutual understanding of the

needs and plans of users and developers. needs and plans of users and developers. Provide the Geant4 Collaboration with the clearest possible Provide the Geant4 Collaboration with the clearest possible

understanding of the needs of its users.understanding of the needs of its users. Promote the exchange of information about physics Promote the exchange of information about physics

validation performed by Geant4 Collaborators and Geant4 validation performed by Geant4 Collaborators and Geant4 users.users.

Promote the exchange of information about user support Promote the exchange of information about user support provided by Geant4 Collaborators and Geant4 user provided by Geant4 Collaborators and Geant4 user communities.communities.

Next Technical Forum meeting @ CERN on February 5Next Technical Forum meeting @ CERN on February 5thth, 2004., 2004.


SummarySummary Geant4 is a worldwide collaboration providing a tool for Geant4 is a worldwide collaboration providing a tool for

simulation of particles interacting with matter.simulation of particles interacting with matter. Geant4’s object-oriented modular structure allows a large Geant4’s object-oriented modular structure allows a large

degree of functionality and flexibility.degree of functionality and flexibility. Geant4 can handle most complicated and realistic geometries.Geant4 can handle most complicated and realistic geometries. Geant4 provides sets of alternative physics models so that Geant4 provides sets of alternative physics models so that

users can choose appropriate models.users can choose appropriate models. Geant4 is being used by not only high energy and nuclear Geant4 is being used by not only high energy and nuclear

physics but also accelerator physics, astrophysics, space physics but also accelerator physics, astrophysics, space science and medical and other applications.science and medical and other applications.

Geant4 Collaboration offers extensive user supports.Geant4 Collaboration offers extensive user supports.

http://cern.ch/geant4/http://cern.ch/geant4/