Geant4 status and applications John Apostolakis, CERN for Geant4 collaboration.
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Transcript of Geant4 status and applications John Apostolakis, CERN for Geant4 collaboration.
Geant4 status and applications
John Apostolakis, CERNfor Geant4 collaboration
212th December 2001
Contents
Geant4’s kernelEM Physics processes
Comparisons with dataHadronic framework, models
Utilization of Geant4
Status and plans
Geant4 4.0 to be released Friday 14th
312th December 2001
GEANT 4
Detector simulation tool-kit for HEP offers alternatives, allows for tailoring
Software Engineering and OO technology provide the method for building, maintaining it.
Requirements from: LHC heavy ions, CP violation, cosmic rays medical and space science applications
World-wide collaboration
412th December 2001
Geant4 Collaboration
Collaborators also from non-member institutions, including
Budker Inst. of PhysicsIHEP Protvino
MEPHI Moscow Pittsburg University
512th December 2001
Geant4 Capabilities
Powerful structure and kernel tracking, stacks, geometry, hits, …
Extensive & transparent physics models electromagnetic, hadronic, …
Framework for fast simulationAdditional capabilities/interfaces
persistency, visualization, ...
612th December 2001
Geant4 kernelCreates & manages runs, events, tracks
a run is configuration of geometry, physics & event generator.
Allows particles to be prioritized easily at no cost 3 default stacks, postponement.
Tracking is general (unique) physics lists can be tailored for different use cases
Enables the creation of user-defined hits able to handle pile-up.
Versatile volumes and navigator for Geometry
712th December 2001
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
Geant4 geometry: what it doesGeant4 geometry: what it does
812th December 2001
Propagating in a field
Charged particles follow paths that approximate their curved trajectories in an electromagnetic field.
It is possible to tailor the accuracy of the splitting of the curve
into linear segments, the accuracy of each intersection of a
volume boundary,trading accuracy against performance.
These can be set to different values for a single volume or for a hierarchy.
912th December 2001
Electromagnetic processes
Initial goal (RD44) was to create EM physics at least at equivalent to Geant-3
New concepts were pursued:Distinction between production
threshold and tracking cutExpressing production cuts in terms of
range instead of energyCreating an effective range from the
distance to the nearest boundary
1012th December 2001
Electromagnetic processes
Processes new to Geant4Multiple Scattering: new model
includes lateral displacement no path length restriction
New process: Transition radiation from physics models
Photo-Absorption Ionisation model Alternative energy loss
Referred to as PAI model
1112th December 2001
Electromagnetic physics
Gammas: Gamma-conversion, Compton scattering, Photo-electric effect
Leptons(e, ), charged hadrons, ions Energy loss (Ionisation, Bremstrahlung) or PAI model energy loss,
Multiple scattering, Transition radiation, Synchrotron radiation,
Photons: Cerenkov, Rayleigh, Reflection, Refraction, Absorption,
Scintillation
High energy muons and lepton-hadron interactions
Alternative implementation (“low energy”) for applications that need to go below 1 KeV Down to 250eV (e+/), O(0.1) m for hadrons
1212th December 2001
Shower profile
1 GeV electron in H2O
G4, DataG3
Good agreement seen with the data
1412th December 2001
Cuts, in kernel & user hook
No tracking cut particles are tracked down to zero energy, range
Coherent “production cuts” for secondaries 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 EnergyGeant3 used cuts in Energy - inefficientsignificant gain in results quality vs CPU usage
User can cut in Energy, track length, TOF ..
1512th December 2001
GEANT4 5cm Pb, CO2, Pb, CO2
Cut: 2mm
Pb 2.5 MeV
CO2 55keV
GEANT3
1612th December 2001
Changing cutsResults much
more stable in variation of cuts even track length
Also see shower profiles for different cuts (next slide) between 10mm
and 50 microns
1712th December 2001
PbWO4
5 GeV e-
1812th December 2001
Secondaries produced only if they could escape
Lead CO2 Lead CO2
Range < safetySecondaries
CANNOT leave Pb:
NOT produced
Range > safety
Secondaries could leave Pb: produced
1912th December 2001
Sampling calorimeter
Sampling calorimeter visible energy
tests all EM
processes for e-, e+ and photon
Data from Sicapo Col. NIM A332 (85-90) 1993
2012th December 2001
Alternatives for Energy Loss
‘Standard’ differentialExtended down to 1 KeVCreates more secondaries near volume borders
Photo-absoption Ionisation model increased precision suited for gases/thin absorbers
Utilised in ATLAS TRT detector
‘Low-energy’ down to 250 eV with shell effects, …
Integral Energy Loss processes Current implementation withdrawn for now
(maintenance/uses)
2112th December 2001
Multiple scattering model
A new model for multiple scattering based on the Lewis theory is implemented since public release in 1998.
It randomizes momentum direction and displacement of a track. Step length, time of flight, and energy loss along
the step are affected, and
It does not constrain the step length.
2212th December 2001
Multiple scattering
Examples of comparisons: 15.7 MeV e-
on gold foil
(figure this page)
Thanks to L. Urban
Angle (deg)
2312th December 2001
Multiple Scattering: One new development
Included in Geant4 4.0Thanks to L.Urban
2412th December 2001
Low energy EM processes
Photons, electrons down to 250 eV Xsec from EADL
libr. Thanks to
M.G. Pia,P. Nieminen, ..
Hadron EM interactions
See 5-001 for an overview of Geant4 Low Energy EM Physics
Photon transmission through 1 mm Pb, showing shell effects
E(KeV)
2512th December 2001
Comparison projects
Established join projects for comparing Geant4 with experiment or test-beam data. Results of EM comparisons: 2000-2001.
Collaboration with experiments ATLAS (projects with data of test beams of 4
calorimeters) BaBar (with experiment data for tracker, drift chamber)
Following slides are taken from the presentations of the experiments at conferences & workshops For latest example: see presentation of D. Barberis at LC workshop,
CERN 15 Nov 2001.
2612th December 2001
2712th December 2001
Thanks to R. Manzini, P. Loch, Atlas FCAL
2912th December 2001
Atlas FCal1 electron Energy resolution
Thanks to Rachid Manzini& Peter Loch& Atlas FCAL
3012th December 2001
A 50 GeV e- in the Atlas EM barrel calorimeter
3112th December 2001
Liquid Argon EM Calorimetry muons in LAr EM Barrel
Thanks to G. Parrour, K. KordasAtlas LAr
3212th December 2001
Liquid Argon EM Calorimetry
electrons
in LAr EM Barrel
Thanks to Gaston Parrour, Kostas Kordas,
Atlas LAr
Linearity of response: - within 0.5%
3312th December 2001
Liquid Argon EM Calorimetry
• Geant4 describes better than Geant3 energy deposits as measured with muon test beam data – agreement G4-test beam is within 1%
• Geant4 (as well as Geant3) describes well the linearity of electron response
• Geant4 predicts larger energy resolution for electrons that Geant3. Direct comparison with test beam data still in progress
3412th December 2001
Liq Argon Hadronic Calorimetry
pion shower in LArHadronic End Cap
electron energy resolution in LAr Hadronic End Cap
3512th December 2001
Liquid Argon Hadronic Calorimetrypion energy resolution inLAr Hadronic End Cap
• Electrons:
•Geant4 predicts less visible energy in LAr than Geant3 (~3%) and more energy in absorber (~0.1%). Total energy is the same
•energy resolution well reproduced by Geant3: Geant4 gives too good resolution
• Pions:
•first results of simulation with Geant4 look reasonable
•more detailed comparisons with test beam data in progress
•open questions being discussed with Geant4 people
3612th December 2001
Tile Calorimeter: electrons
Visible energy vs impact position for 20 GeV and 100 GeV electrons
Electron energy resolution
• Electron energy resolution somewhat too good: sampling term 16% instead of 24% (was the same for Geant-3)
• Visible energy vs impact point has the correct shape but amplitude of variations and energy dependence do not match test beam data
=0.35 in Tilecal module 0
3712th December 2001
Observations on the comparisons
Geant4 results are more stable than Geant3Many results of Geant4 versus data
reasonable agreement seen in many observables, issues/differences exist that need to be resolved.
Invaluable feedback obtained, with improvements developed and planned.
The good spirit of the collaboration has allowed us to resolve many issues (THANKS).
3812th December 2001
Hadronic processes
Five level implementation framework allows models to be used in combination at
different levelsSolving the mix and match problem in the framework
Variety of models and cross-sections for each energy regime, particle type, material alternatives with different strengths and
computing resource requirementsComponents can be assembled in an
optimized way for each use case. A simple example is illustrated in figure (next
page)
3912th December 2001
Assembling processes
Illustrative example of assembling models into an inelastic process for set of particles Uses levels 1 &
2 of framework
Ene
rgy
Element
Pre-compoundmodel
CHIPS
QGSM Parame-terized
particle
4012th December 2001
Hadronic processesEach hadronic process may have one or more
cross section data sets and final state production models
associated with it. Each one has its own applicability.
We define “data set” and “model” broadly A “data set” is an object that encapsulates
methods and data for calculating total cross sections.
A “model” is an object that encapsulates methods and data for calculating final states.
4112th December 2001
Hadronic processes at rest
At Rest processes pion absorption kaon absorption neutron capture antiproton annihilation antineutron annihilation mu capture
At Rest processes may generate secondaries after some time interval.
4212th December 2001
Hadronic processes in flightFour types of processes
Elastic scattering Inelastic scattering Fission Capture
Examples Parameterization driven models originally based
on GHEISHA with many improvements Data driven models based on ENDF/B-VI Theory driven models for inelastic scattering
4312th December 2001
Modeling approaches
1. Data driven approachNeutrons
from numerous evaluated data librariesdown to thermal energies, up to 20 MeV
Isotope production (see next slide) Induced Fission & Capture (H.Fesefeldt)
used above 20 MeV
Photon-evaporation, radioactive decay, etc.2. Parameterized models
Gheisha + fixes + new parameterizations (H.F, TRIUMF)
4412th December 2001
Modeling approaches (cont.)
3. Theoretical models, from low E to high E Pre-Compound Model + Evaporation Phase Cascades, CHIPS and QMD models String models
Excitation, fragmentation, hadronisation models
Interface to event generator(s)In future
4512th December 2001
Pre-Compound Model & Evaporation Phase
Traditional pre-equilibrium model as good as existing ones
Evaporation: Weisskopf-Ewing model Fermi breakup model Model for fission Multi-fragmentation model (Bondorf) Photon Evaporation only missing Internal Conversion
(suppressed by more than 10^4, funding expected) Future: 2nd Pre-Compound, from HETC re-eng. (in
2002)
4612th December 2001
Cascade energy range
Parameterized Chiral Invariant Phase Space
decay,“CHIPS” 1st implementation now (Jefferson Lab.) collaboration milestone 2001 (in release)
Bertini cascade (from HETC) collaboration milestone for 2001 (missed)
Kinetic model (INFN, Frankfurt): future
Further future: Relativistic QMD (Frankfurt), rewrite of INUCL code (Helsinki)
4712th December 2001
String models
FTF string model, derived from Fritiof but no Rutherford scattering
Quark Gluon String model (~ Dual Parton) for proton, neutron, K+/K- induced reaction
string decay as in JETSETfollowing Kaidalov’s formulationusing FTF algorithm for energy transfer in case of
single diffraction (~6% cases)future: K0, , anti-nucleon induced reactions
4812th December 2001
Future additions
Quark molecular dynamics model (Frankfurt)
Nucleus-Nucleus via QMD (Frankfurt) for light nuclei using pre-compound and
cascades ablation/abration model
Parton cascade (ansatz of K. Geiger) ‘Re-use’ of Pythia7
for hadron-nuclear & hadron-hadron interactions
4912th December 2001
Some of the Improved Hadronic Physics 1999-2001Neutron & proton induced isotope production
models up to 100 MeV (J.P. Wellisch)
Multi-fragmentation and pre-compound redesign & refinement (V. Lara)
Additional string model (J.P.Wellisch)
for proton, neutron, K+/K- induced reactionsSpecial cross-section classes for neutron, proton,
and ion induced reactions (D. Axen, M. Laidlaw, J.P.W.)
Retuning of High Energy Models (H. Fesefeldt) | (JPW)
Doppler broadening of neutron X-section on the fly
5012th December 2001
Isotope Production
Isotopes produced by neutrons on Lead 208
Small dots: evaluated data
Circles with error bars: Geant4 latest model included
since Geant4 1.0
J.P.Wellisch
5112th December 2001
CHIPS
New physics model/event generatorFrom ~100 MeV to ~10 GeVApplications to date:
Pbar annihilation at rest Pi capture Gamma-nucleus interactions Intranuclear transport
after high energy interaction
Schedule for release end 2001
5212th December 2001
Pion capture on 12 C nucleus
5312th December 2001
Example gamma nuclear reactions
Thanks to M. Kossov, J.P. Wellisch, P.V. Degtaryenko
For more on Hadronic Physics in Geant4, see the presentation in Track 5 by J.P. Wellisch, 5-004
“Hadronic Shower Models in Geant4: Validation strategy and Results”
5412th December 2001
Atlas Tile Calorimeter: pions First Results of First Results of
parameterised models in GEANT4 similar to GHEISHA in GEANT3parameterised models in GEANT4 similar to GHEISHA in GEANT3
E(GeV)
Thanks to Atlas TileCal
5512th December 2001
Parameterization/Fast SimulationFast 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
User must create his/her own (for now)This parameterisation scheme utilised
For fast simulation of TR, PAI
5612th December 2001
Visualization
Much 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 Editors for geometry, EM
physics code generation
5712th December 2001
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
5812th December 2001
Courtesy of A. Pfeiffer, CERN
Example: AIDA & Analysis Tools
Similar approach:Similar approach:• graphics• (G)UI• persistency • etc.
Interface to external tools
No dependence
Minimize coupling of components
Java Analysis Studio
Lizard
Through abstract interfaces
AIDA
5912th December 2001
Variance reduction Geant4 has one event biasing option for the transportation of “low energy”
neutrons. The formulae are derived from MARS95.
Producing small number of secondaries weighted to represent a large number of particles.• This option is now available for neutrons of E < 5 GeV.
It is possible to use other methods now, but in user code.
New general purpose built-in methods are being created: Importance biasing: splitting/roulette. Leading particle ‘filters’ X section enhancement
Prototype implementations and applications are simple to create, given the flexibility of the toolkit ‘Friendly-user’ use will be available soon – contact us We intend to release them in 2002 – exact time to be determined.
6012th December 2001
Use of Geant4
Three years from the first Geant4 public release, major experiments has already started to use Geant4 intensively: BaBar: Full migration from G3 based simulator HARP: Running today with G4 as only simulation Atlas : G4 validation for all detector test beams 2000/1 CMS : Simulation of full detector based on G4 in 2001
Usage of Geant4 has expanded to fields other than HEP. Accelerator applications (T9 Harp, Muon fact.) Space and medical applications
6112th December 2001
BaBar full simulator ‘BOGUS’
BaBar Object-oriented Geant4-based Unified SimulatorOver 100 million events generated (by mid-Nov.)
Robust - Crash rate less than 1 per million events No significant memory leaks Performance as good as BBSIM (Geant3)
Comparisons with experimental data and BBSIM, were undertaken, using the full reconstruction chain.
Decision was taken to move to Geant4 and to utilize it exclusively for 2001 data. Full production with BOGUS is ongoing: plans to simulate
200 million events in 2001, 500 million by early 2002.
6212th December 2001
6312th December 2001
6412th December 2001
Transition Radiation Trackersupport and alignment plate
straws
radiator matrix
carbon fiber shell
zoom of module end plate
Thanks to Atlas TRT
6512th December 2001
TRT: Energy Loss in Straws
300 GeV muons
20 GeV pions
20 GeV electrons
Energy loss measured in ATLAS test beam compared to Geant-3 and to Geant-4 simulations (PAI model) including effects of detector and electronics (K.A.Assamagan):
• spectra match reasonably for different particles and energies
• some more checks needed for electrons
Thanks to Atlas TRT
6612th December 2001
ESA Space Environment & Effects Analysis Section
X-Ray Surveys of Asteroids and Moons
Induced X-ray line emission:indicator of target composition(~100 m surface layer)
Cosmic rays,jovian electrons
Geant3.21
ITS3.0, EGS4
Geant4
C, N, O line emissions included
Solar X-rays, e, p
Courtesy SOHO EIT
6712th December 2001
0 10 20 30 40 500,0
0,2
0,4
0,6
0,8
1,0
1,2 Simulazione Nucletron Misure
Dose %
Distanza lungo Z (mm)Distance along Z (mm)
SimulationNucletronData
-60
-55
-50
-45
-40
-35
-30
-25
-20
-15
-10
-5
0-40 -30 -20 -10 0 10 20 30 40
Distanza trasversale (mm)
80% 60% 40% 20% 10%
Pro
fon
dità
(m
m)
Transverse distance (mm)
De
pth
(m
m)
Experimental validationLeipzig applicators
Courtesy F. Foppiano, M. Tropeano
BrachytherapyBrachytherapy at the Natl. Inst. for Cancer Research (IST-Genova)
Superficial brachytherapy
6812th December 2001
PerformanceGeometry navigation
Geant4 automatically optimizes the user’s geometrical description. And it provides faster navigation than optimized Geant3 descriptions.
EM Physics computing performance goals For the same physics performance, we seek speed at
the level of Geant3 or better. Keeping physics performance constant, optimise the
speed that maintains the performance.In two current speed benchmarks (thin silicon &
simplified sampling calorimeter) these goals are achieved.
6912th December 2001
PerformanceIn experimental setups
Atlas EM Barrel: comparable performance Atlas FCAL: Geant4 is 3x faster than Geant3 BaBar: comparable performance.
Our goal is that Geant4 is at least as fast as Geant3 in almost every case when its power and features are well exploited. And, where required, ‘new’ techniques including
shower parameterisation can be used to obtain large speedups (in acceptable trade-off with accuracy)
7012th December 2001
The next release of Geant4
The next release of Geant4 is 4.0, a major release on December 14th has been scheduled to include New theoretical hadronic models
CHIPS for gamma-Nucleus, capture and intranuclear transportCascade+Pre-compound re-engineered from HETC (not ready)
Ability to reduce initialisation timeBy saving/retrieving physics processes’ table
A field can now be set to any volume or volume treeOverriding a potential global ‘default’ field
• Note that, for now, all fields must be addressed in global coordinates
Ability to set different Cuts for different regionsIn a first implementation (for urgent clients)
7112th December 2001
Next release New UI option: ‘GAG’ as plug-in version for JAS
enabling user to control the execution of Geant4, while taking histograms
In Visualization Completion of the ‘new’ visualization commands. The first release of the XML ==> DAWN file converter
Analysis - Example utilising new AIDA interfaces, version 2.2 That includes support for tuple, cloud of points & plotter.
In addition all current fixes, and numerous improvements in functionality and physics modelling are also included.
7212th December 2001
Domain decomposition
hierarchical structure of
sub-domains
Geant4 architecture
Uni-directional flow of
dependencies
Software Engineeringplays a fundamental role in
Geant4User Requirements
• formally collected• systematically updated• PSS-05 standard
Software Process• spiral iterative approach• regular assessments and improvements• monitored following the ISO 15504 model
Quality Assurance• commercial tools• code inspections• automatic checks of coding guidelines• testing procedures at unit and integration level• dedicated testing team
Object Oriented methods• OOAD• use of CASE tools
• essential for distributed parallel development• contribute to the transparency of physics
Use of Standards • de jure and de facto
7312th December 2001
Some future plans/ directions
To facilitate the specialization of those parts of physics lists that vary between use cases.
To create and distribute “educated guess” physics lists corresponding to the major use cases of Geant4 involving hadronic physics, As an aid and starting point for users.
To enable the use of different models for EM physics (eg Ionisation) in one application likely through the use of ‘models’ etc
7412th December 2001
Summary
Geant4 is in production use today in running HEP experiments (BaBar, HARP)
Results of comparing Geant4 versus data are growing month by month, have provided important ‘yardsticks’.
Geant4 has demonstrated important strengths: stability of results, flexibility, transparency.
Refinements & development are ongoing.
http://cern.ch/geant4/
7512th December 2001
THE END
Note that it was not possible to give appropriate credit here to all those who have contributed to
the Geant4 toolkit, the accompanying tools, the topics presented, all the applications featured.Or to express the appreciation toUsers, especially the donors of feedback
THANKS TO ALL