1. Maria Grazia Pia 1 Overview of the Maria Grazia Pia INFN Genova, Italy and CERN/IT Maria.Grazia.Pia@cern.ch Object Oriented Simulation Toolkit

2. Maria Grazia Pia 2 Once upon a time there was a X- ray telescope... Courtesy of NASA/CXC/SAO

3. Maria Grazia Pia 3 Chandra X-ray Observatory Status Update September 14, 1999 MSFC/CXC CHANDRA CONTINUES TO TAKE SHARPEST IMAGES EVER; TEAM STUDIES INSTRUMENT DETECTOR CONCERN Normally every complex space facility encounters a few problems during its checkout period; even though Chandra’s has gone very smoothly, the science and engineering team is working a concern with a portion of one science instrument. The team is investigating a reduction in the energy resolution of one of two sets of X-ray detectors in the Advanced Charge-coupled Device Imaging Spectrometer (ACIS) science instrument. A series of diagnostic activities to characterize the degradation, identify possible causes, and test potential remedial procedures is underway. The degradation appeared in the front-side illuminated Charge-Coupled Device (CCD) chips of the ACIS. The instrument’s back-side illuminated chips have shown no reduction in capability and continue to perform flawlessly. An excerpt of a press release Courtesy of NASA/CXC/SAO

4. Maria Grazia Pia 4 l Radiation belt electrons? l Scattered in the mirror shells? l Effectiveness of Magnetic “brooms” l Electron damage mechanism? - NIEL? l Other particles? Protons, cosmics l Path to CCD? Wall penetration? What can affect CCD’s on X-ray astronomy missions? éProposal: set the problem up in Geant4 as a case-study.

5. Maria Grazia Pia 5 XMM

6. Maria Grazia Pia 6 ESA Space Environment & Effects Analysis Section EPIC RGS Q1Q1 Q1Q1 Q2Q2

7. Maria Grazia Pia 7 ESA Space Environment & Effects Analysis Section CCD displacement damage: front vs. back-illuminated. 30  m 2  m 30  m 2  m 30  m Si  ~1.5 MeV p+ Active layer Passive layer “Electron deflector” EPIC RGS Low-E (~100 keV to few MeV), low- angle (~0°-5°) proton scattering: Obscure problem; not much analysed

8. Maria Grazia Pia 8 How well can Geant4 simulate low energy protons? Courtesy of R. Gotta, Thesis

9. Maria Grazia Pia 9 What happened next? XMM was launched on 10 December 1999 from Kourou EPIC image of the two flaring Castor components and the brighter YY Gem Courtesy of

10. Maria Grazia Pia 10 3Main features of the Geant4 toolkit n the kernel n geometry n physics n other tools Outline 3What is Geant? 3Status of Geant3 and motivations for Geant4 3The Geant4 R&D phase: RD44 3The Geant4 Collaboration 3The role of software engineering and OO technology 3Performance 3A selection of Geant4 applications 3Conclusions

11. Maria Grazia Pia 11 The role of Geant ]Geant is a simulation tool, that provides a general infrastructure for l the description of geometry and materials l particle transport and interaction with matter l the description of detector response l visualisation of geometries, tracks and hits ]The user develops the specific code for l the primary event generator l the geometrical description of the set-up l the digitisation of the detector response

12. Maria Grazia Pia 12 The past: Geant3 ]Geant 3 l has been used by most major HEP experiments l Frozen since March 1994 (Geant3.21) l ~200K lines of code l equivalent of ~50 man-years, along 15 years l used also in nuclear physics experiments, medical physics, radiation background studies, space applications etc. ]The result is a complex system l because its problem domain is complex l because it requires flexibility for a variety of applications l because its management and maintenance are complex ]It is not self-sufficient l hadronic physics is not native, it is handled through the interface to external packages

13. Maria Grazia Pia 13 New simulation requirements ]Very high statistics to be simulated l robustness and reliability for large scale production ]Exchange of CAD detector descriptions ]Transparent physics for validation of physics results ]Physics extensions to high energies l LHC, cosmic ray experiments... ]Physics extensions to low energies l space applications, medical physics, X-ray analysis, astrophysics, nuclear and atomic physics... ]Reliable hadronic physics l not only for calorimetry, but also for PID applications (CP violation experiments)...etc. User requirements formally collected and coded according to PSS05 standard èGeant4 User Requirements Document

14. Maria Grazia Pia 14 What is Geant4? OO toolkit for the simulation of next generation HEP detectors...of the current generation too...not only of HEP detectors èalready used also in nuclear physics, medical physics, space applications, radiation background studies etc. ]It is also an experiment of distributed software production and management, as a large international collaboration with the participation of various experiments, labs and institutes ]It is also an experiment of application of rigorous software engineering and Object Oriented technologies to the HEP environment

15. Maria Grazia Pia 15 ]Milestones: end 1995 l OO methodology, problem domain analysis, full OOAD l tracking prototype, performance evaluation ]Milestones: spring 1997  -release with the same functionality as Geant 3.21 l persistency (hits), ODBMS l transparency of physics models ]Milestone: July 1998 public  -release ]Milestone: end 1998 l production release: Geant4.0, end of the R&D phase èAll milestones have been met by RD44 ]Reconfiguration at the end of the R&D phase l International Geant4 Collaboration sincel 1/1/1999 l Management of the production phase l Continuing R&D also in the production phase Approved as R&D end 1994 (RD44) > 100 physicits and software engineers ~ 40 institutes, international collaboration responded to DRCC/LCB

16. Maria Grazia Pia 16 Geant4 Collaboration n Atlas, BaBar, CMS, HARP, LHCB n CERN, JNL,KEK, SLAC, TRIUMF n ESA, Frankfurt Univ., IGD, IN2P3, Karolinska Inst., Lebedev, TERA n COMMON (Serpukov, Novosibirsk, Pittsburg etc.) n other memberships currently being discussed ]Collaboration Board l manages resources and responsibilities ]Technical Steering Board l manages scientific and technical matters ]Working Groups l do maintenance, development, QA, etc. Members of National Institutes, Laboratories and Experiments participating in Geant4 Collaboration acquire the right to the Production Service and User Support For others: free code and user support on best effort basis Budker Inst. of Physics IHEP Protvino MEPHI Moscow Pittsburg University New organization for the production phase, MoU based ë Distribution, development and User Support

17. Maria Grazia Pia 17 Software Engineering ]Software process l based on Booch methodology l spiral type, with cycles of design- implementation iterations l OOAD l Development l Evolution l Maintenance in a worldwide collaboration! Software Engineering plays a fundamental role in Geant4 v Software process v User requirements v OOAD v Quality Assurance ]User Requirements l Collected initially and systematically updated l Coded according to ESA PSS-05 standard

18. Maria Grazia Pia 18 OO technologies èOpen to evolution l extensibility, implementation of new models and algorithms without interfering with existing software l the user can extend the toolkit with his/her model and data OO design fundamental for distributed parallel approach l every part can be developed, refined, maintained independently l Problem domain decomposition and OOAD result into a unidirectional dependency of class categories ]Transparency l decoupling from implementation ]Flexibility l alternative models and implementations ]Interface to external software, without dependencies l databases for persistency l visualisation libraries l tools for UI l etc.

19. Maria Grazia Pia 19 Geant4 architecture exploits advanced Software Engineering techniques and Object Oriented technology to achieve transparency of physics implementation.

20. Maria Grazia Pia 20 Quality Assurance ]Extensive use of Quality Assurance systems l fundamental for a toolkit of wide public use ]Commercial tools l Insure++, Logiscope etc. ]C++ coding guidelines l scripts to verify their applications automatically ]Code inspections l within working groups and across groups ]Testing l Unit testing n in most cases down to class level granularity l Integration testing n sets of logically connected classes l Test-bench for each category n eg.: test-suite of 375 tests for hadronic physics parameterised models l System testing n exercising all Geant4 functionalities in realistic set-ups l Physics testing n comparisons with experimental data l Performance Benchmarks

21. Maria Grazia Pia 21 Standards Units l Geant4 is independent from the system of units l all numerical quantities expressed with their units explicitly l user not constrained to use any specific system of units Based on standards, ISO and de facto ] OpenGL e VRML for graphics ] CVS for code management ] C ++ as programming language ] STEP engineering and CAD systems ] ODMG RD45 Have you heard of the “incident” with NASA’s Mars Climate Orbiter ($125 million)?

22. Maria Grazia Pia 22 What is needed to run Geant4 ]Platforms l DEC, HP, IMB-AIX, SUN, (SGI): native compilers, g++ l Linux: g++ l Windows-NT: Visual C++ ]Commercial software l ObjectStore STL (optional) ]Free software l CVS l gmake, g++ l CLHEP ]Graphics l OpenGL, X11, OpenInventor, DAWN, VRML... l OPACS, GAG, MOMO... ]Persistence l it is possible to run in transient mode l in persistent mode use a HepDB interface, ODMG standard

23. Maria Grazia Pia 23 The Geant4 kit ]Code l ~1M lines of code, ~2000 classes (continuously growing) l publicly available from the web ]Documentation l 6 manuals l publicly available from the web ]Examples l distributed with the code l navigation between documentation and examples code

24. Maria Grazia Pia 24 The kernel ]Run and event l the Run Manager can handle multiple events n possibility to handle the pile-up l multiple runs in the same job n with different geometries, materials etc. l powerful stacking mechanism n three levels by default: handle trigger studies, loopers etc. ]Tracking l decoupled from physics: all processes handled through the same abstract interface l tracking is independent from particle type l it is possible to add new physics processes without affecting the tracking Geant4 has only production thresholds, no tracking cuts l all particles are tracked down to zero range l energy, TOF... cuts can be defined by the user

25. Maria Grazia Pia 25 Geometry Multiple representations ]CGS (Constructed Solid Geometries) l simple solids ]STEP extensions l polyhedra,, spheres, cylinders, cones, toroids, etc. ]BREPS (Boundary REPresented Solids) l volumes defined by boundary surfaces l include solids defined by NURBS (Non-Uniform Rational B-Splines) ]External tool for g3tog4 geometry conversion ]CAD exchange l interface through ISO STEP (Standard for the Exchange of Product Model Data) ]Fields l of variable non-uniformity and differentiability l use of various integrators, beyond Runge-Kutta l time of flight correction along particle transport Role: detailed detector description and efficient navigation

26. Maria Grazia Pia 26 Things one can do with Geant4 geometry One can do operations with solids These figures were visualised with Geant4 Ray Tracing tool...and one can describe complex geometries, like Atlas silicon detectors

27. Maria Grazia Pia 27 Borexino at Gran Sasso Lab. BaBar at SLAC Chandra (NASA) XMM-Newton (ESA) ATLAS at LHC, CERN GLAST (NASA) CMS at LHC, CERN A selection of geometry applications

28. Maria Grazia Pia 28 Processes Processes describe how particles interact with material or with a volume itself ]Three basic types l At rest process (e.g. decay at rest) l Continuous process (e.g. ionization) l Discrete process (e.g. decay in flight) ]Transportation is a process l interacting with volume boundary ]A process which requires the shortest interaction length limits the step

29. Maria Grazia Pia 29 Physics From the Minutes of LCB (LHCC Computing Board) meeting on 21 October, 1997: “It was noted that experiments have requirements for independent, alternative physics models. In Geant4 these models, differently from the concept of packages, allow the user to understand how the results are produced, and hence improve the physics validation. Geant4 is developed with a modular architecture and is the ideal framework where existing components are integrated and new models continue to be developed.”

30. Maria Grazia Pia 30 The approach to physics ]Ample variety of independent, alternative physics models available in Geant4 ]No more black boxes of packages Users are directly exposed to the physics they use in their simulation ]This approach is fundamental for the validation of the experiments’ physics results

31. Maria Grazia Pia 31 Transparency of Geant4 physics ]No “hard coded” numbers ]Explicit use of units throughout the code ]Separation between the calculation of cross sections and the generation of the final state ]Calculation of cross-sections independent from the way they are accessed (data files, analytical formulae etc.) ]Distinction between processes and models ]Cuts in range (rather than in energy, as usual) l consistent treatment of interactions near boundaries between materials ]Modular design, at a fine granularity, to expose the physics l physics independent from tracking ]Public distribution of the code, from one reference repository worldwide

32. Maria Grazia Pia 32 Physics: general features ]Abstract interface to physics processes l tracking independent from processes ]Distinction between processes and models l often multiple models for the same process ]Data encapsulation and polymorfism l Transparent access to cross sections, from files, interpolation from tables, analytical formulae etc. l Distinction between the calculation of cross sections and their use l Calculation of the final state independent from tracking ]Uniform treatment of electromagnetic and hadronic physics ]Open system Users can easily create and use their own models

33. Maria Grazia Pia 33 Data libraries ]Systematic collection and evaluation of experimental data from many sources worldwide ]Databases GENDF/B, JENDL, FENDL, CENDL, ENSDF,JEF, BROND, EFF, MENDL, IRDF, SAID, EPDL, EEDL, EADL, SANDIA, ICRU etc. ]Collaborating distribution centres G NEA, LLNL, BNL, KEK, IAEA, IHEP, TRIUMF, FNAL, Helsinki, Durham, Japan etc. ]The use of evaluated data is important for the validation of physics results of the experiments

34. Maria Grazia Pia 34 Electromagnetic physics  Comparable to Geant3 and EGS already in the  -release ]Substantial further extensions ]Multiple alternatives for various processes ]High energy extensions models for  up to PeV l fundamental for LHC experiments, cosmic ray experiments etc. ]Low energy extensions e,  down to 250 eV (EGS, ITS etc. to 1 keV, Geant3 to 10 keV)) l low energy hadrons and ions models based on Ziegler and ICRU data and parametrisations l models for antiprotons (positrons in progress) l fundamental for space and medical applications, neutrino experiments, antimatter spectroscopy etc.

35. Maria Grazia Pia 35 E.M. processes in Geant4 3 multiple scattering 3 energy loss 3 Bremsstrahlung 3 ionisation 3 annihilation 3 photoelectric effect 3 Compton scattering 3 pair production 3 synchrotron radiation 3 transition radiation 3 Cherenkov 3 Rayleigh effect 3 rifraction 3 reflection 3 absorption 3 scintillation 3 fluorescence 3 Auger (in progress)

36. Maria Grazia Pia 36 Selection of e.m. physics results BackscatteringMultiple scattering

37. Maria Grazia Pia 37 Low energy e.m. extensions e,  down to 250 eV (positrons in progress) (EGS, ITS to 1 keV, Geant3 to 10 keV) Fundamental for space and medical applications, neutrino experiments, antimatter spectroscopy etc. Low energy hadrons and ions models based on Ziegler and ICRU data and parameterisations Barkas effect: models for antiprotons

38. Maria Grazia Pia 38 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 Solar X-rays, e, p Courtesy SOHO EIT C, N, O line emissions included Low energy e.m. extensions

39. Maria Grazia Pia 39 Photon attenuation coefficient in water 1.000.000 photons generated, 120 sec on an Intel PC 300 MHz Brachytherapy at IST Genova, Italian National Institute for Cancer Research Low energy e.m. extensions Courtesy of IST

40. Maria Grazia Pia 40 High energy e.m. extensions High energy  Courtesy of L3 Models for muons extended up to the PeV scale

41. Maria Grazia Pia 41 Examples of application of Geant4 e.m. physics Courtesy of CMS Sampling calorimeter

42. Maria Grazia Pia 42 Hadronic physics ]Completely different approach w.r.t. the past l transparent l native no longer interface to external packages l clear separation between data and their use in algorithms ]Cross section data sets l transparent and interchangeable ]Final state calculation l models by particle, energy, material

43. Maria Grazia Pia 43 Completeness of Geant4 hadronic physics ]Ample variety of models l the most complete hadronic simulation kit on the market l alternative and complementary models l it is possible to mix-and-match, with fine granularity l data-driven, parameterised and theoretical models êConsequences for the users l no more confined to the black box of one package l the user has control on the physics used in the simulation, which contributes to the validation of physics results

44. Maria Grazia Pia 44 Hadronic physics Parameterised and data-driven models (1) Based on experimental data ]Some models originally from GHEISHA l completely reengineered into OO design l refined physics parameterisations ]New parameterisations l pp, elastic differential cross section l nN, total cross section l pN, total cross section l np, elastic differential cross section  N, total cross section  N, coherent elastic scattering p elastic scattering on Hydrogen

45. Maria Grazia Pia 45 Hadronic physics Parameterised and data-driven models (2) Other models are completely new, such as stopping particles (  -, K - ) l neutron transport l isotope production Neutrons Courtesy of CMS nuclear deexcitation absorption Stopping  MeV Energy All databases existing worldwide used in neutron transport Brond, CENDL, EFF, ENDFB, JEF, JENDL, MENDL etc.

46. Maria Grazia Pia 46 Hadronic physics Theoretical models ]They fall into different parts l the evaporation phase l the low energy range, pre-equilibrium, O(100 MeV), l the intermediate energy range, O(100 MeV) to O(5 GeV), intra-nuclear transport l the high energy range, hadronic generator régime ] Geant4 provides complementary theoretical models to cover all the various parts ] Geant4 provides alternative models within the same part ] All this is made possible by the powerful Object Oriented design of Geant4 hadronic physics ] Easy evolution: new models can be easily added, existing models can be extended

47. Maria Grazia Pia 47 A sample from theory-driven models

48. Maria Grazia Pia 48 An example of user application 123456789101112131415161718192021222324252627 152 cm Copper + 189 mm Plastic CMS HCAL (H2 1996) Test-Beam Setup Courtesy of CMS Collaboration

49. Maria Grazia Pia 49 Event biasing ]Geant4 provides facilities for event biasing ]The effect consists in producing a small number of secondaries, which are artificially recognized as a huge number of particles by their statistical weights ]Event biasing can be used, for instance, for the transportation of slow neutrons or in the radioactive decay simulation

50. Maria Grazia Pia 50 Other components ]Materials l elements, isotopes, compounds, chemical formulae ]Particles l all PDG data l and more, for specific Geant4 use, like ions ]Hits & Digi l to describe detector response ]Persistency l possibility to run in transient or persistent mode l no dependence on any specific persistency model l persistency handled through abstract interfaces to ODBMS ]Visualisation l Various drivers l OpenGL, OpenInventor, X11, Postscript, DAWN, OPACS, VRML ]User Interfaces l Command-line, Tcl/Tk, Tcl/Java, batch+macros, OPACS, GAG, MOMO l automatic code generation for geometry and materials ]Interface to Event Generators l through ASCII file for generators supporting /HEPEVT/ l abstract interface to Lund++

51. Maria Grazia Pia 51 Sector Shielding Analysis Tool CAD tool front-end Delayed radioactivity General purpose source particle module INTEGRAL and other science missions Instrument design purposes Dose calculations Particle source and spectrum Geological surveys of asteroids Modules for space applications Low-energy e.m. extensions

52. Maria Grazia Pia 52 Fast simulation ]Geant4 allows to perform full simulation and fast simulation in the same environment ]Geant4 parameterisation produces a direct detector response, from the knowledge of particle and volume properties l hits, digis, reconstructed-like objects (tracks, clusters etc.) ]Great flexibility l activate fast /full simulation by detector example: full simulation for inner detectors, fast simulation per calorimeters l activate fast /full simulation by geometry region example: fast simulation in central areas and full simulation near cracks l activate fast /full simulation by particle type  example: in e.m. calorimeter e/  parameterisation and full simulation of hadrons l parallel geometries in fast/full simulation example: inner and outer tracking detectors distinct in full simulation, but handled together in fast simulation

53. Maria Grazia Pia 53 Example of integrated Fast/Full Simulation application B aBar O bject-oriented G eant4-based U nified S imulation (BOGUS) l Integrated framework for Fast and Full simulation l Fast simulation available for public use since February 1999 l Integrated in BaBar environment n primary generators, reconstruction, OODB persistency n parameters for materials and geometry shared with reconstruction applications Courtesy of G. Cosmo

54. Maria Grazia Pia 54 Performance ]Various Geant4 - Geant3.21 comparisons l realistic detector configurations l results and plots in l Geant4 Web Gallery (from Geant4 homepage) l RD44 Status Report, 1995 ]Benchmark in liquid Argon/Pb calorimeter l at comparable physics performance Geant4 is faster than (fully optimised) Geant3.21 by n a factor >3 using exactly the same cuts n a factor >10 optimising Geant4 cuts, while keeping the same physics performance l at comparable speed Geant4 physics performance is greatly superior to Geant3.21 ]Benchmark in thin silicon layer l at comparable physics performance Geant4 is 25% faster than Geant3.21 (single volume, single material)

55. Maria Grazia Pia 55 Geant4 features relevant for medical applications ]The transparency of physics ]Advanced functionalities in every domain: geometry, physics, visualisation etc. ]Extensibility in any domain to satisfy new user requirements l thanks to OO technology l open design: new physics, new features can be easily added, without any perturbation to the existing code ]Adopts standards wherever available (de jure or de facto) ]Use of evaluated data libraries ]Quality Assurance based on sound software engineering ]Subject to independent validation by a large user community worldwide ]User support organization by a large international Collaboration of experts

56. Maria Grazia Pia 56 Bragg peak, Magic cube data and Geant4 Experimental data: Bragg peak of a 270 MeV/u carbon ion beam Geant4 and experimental data, PSI test with proton beam distance(cm) Courtesy of INFN Torino

57. Maria Grazia Pia 57 Brachyterapy at Nat. Inst. Cancer Research, Genova ]The source holder is a standard endobronchial treatment catheter, the chamber is a 0.6 cc Capintec chamber connected to a Capintec 192 electrometer ]The IST group follows the direction of Basic Dosimetry on Radiotherapy with Brachytherapy Source of the Italian Association of Biomedical Physics (AIFB) The custom calibration plexiglas jig, used for in air measurements. Courtesy of S. Agostinelli, R. Corvo, F. Foppiano, S. Garelli, G. Sanguineti, M. Tropeano Source anisotropy Geant4 simulation

58. Maria Grazia Pia 58 CT interface and treatment planning Two possible approaches: ]CT interface + Geant4 “full simulation” ]CT interface + Geant4 “fast simulation” (physics processes parameterised through an analytical treatment) ]Geant-based tools for l inverse planning l technique of active dose delivery ]Software interface for Geant4 that reads input data in DICOM3 format under development at Medical Dept., University of Piemonte Orientale and INFN Torino Courtesy of V. Rolando, Univ. Piemonte Orientale

59. Maria Grazia Pia 59 Geant4 for scatter compensation in Megavoltage 3D CT ]Use GEANT4 to obtain digitally reconstructed radiographs (DRRs), including full scatter simulation This represents a great improvement over approaches based on ray- casting Courtesy of IST Genova

60. Maria Grazia Pia 60 In vivo dosimetry for mammography ]TLD characterization for mammography screening l simulation of dose deposition and glow curve ]Mammography simulation l Goal: minimize dose on patient l Comparison between experimental data TLD in vivo dosimetry and Geant4 simulation êActivity at Medical Physics Dept., Umberto I Hospital of Ordine Mauriziano, Torino l in progress

61. Maria Grazia Pia 61 Risk factors ]Performance and adequacy of C++ and OO technologies for HEP simulation were considered risk factors at the beginning of the project êclearly demonstrated that Geant4 satisfies the requirements for use in HEP simulation ]Now? Maturity of the HEP community l to appreciate the need of a new simulation environment l to work in a simulation environment based on advanced software engineering l to invest in learning new technologies

62. Maria Grazia Pia 62 An ambitious project ]Multi-disciplinary Collaboration of n astrophysicists and space scientists n particle physicists n medical physicists n biologists n physicians ]Other applications (not only in space domain) What if the geometry to describe with Geant4 were DNA and the process were mutagenesis? l INFN (Genova, Torino, Cosenza) l ESA l CERN l Istituto Nazionale per la Ricerca sul Cancro Karolinska Institute l PSI l Università del Piemonte Orientale l Università di Pisa First phase of the project: User Requirements Study of radiation damage at the cellular and DNA level in the space radiation environment -sponsored project, in collaboration with

63. Maria Grazia Pia 63 Conclusions ]The software challenge l first successful attempt to redesign a major package of HEP software adopting an Object Oriented environment and a rigorous approach to advanced software engineering ]The functionality challenge l a variety of requirements from many application domains (HEP, space, medical etc.) ]The physics challenge l transparency l extended coverage of physics processes across a wide energy range, with alternative models ]The performance challenge l mandatory for large scale HEP experiments and for other complex applications ]The distributed software development l OOAD has provided the framework for distributed parallel development ]The management challenge l a well defined, and continuously improving, software process has allowed to achieve the goals ]The user support challenge l the user community is distributed worldwide, operating in a variety of domains Geant4 has successfully coped with a variety of challenges Geant4 represents a successful experience for the future generation of experiments

64. Maria Grazia Pia 64 Documentation ]User Documentation l Introduction to Geant4 l Installation Guide l Geant4 User’s Guide - For Application Developers n for those wishing to use Geant4 l Geant4 User’s Guide - For Toolkit Developers n for those wishing to extend Geant4 functionality l Software Reference Manual n documentation of the public interface of all Geant4 classes l Physics Reference Manual n extended documentation on Geant4 physics ]Examples l a set of Novice, Extended and Advanced examples illustrating the main functionalities of Geant4 in realistic set-ups ]The Gallery l a web collection of performance and physics evaluations http://wwwinfo.cern.ch/asd/geant4/reports/gallery/ ]Publication and Results web page http://wwwinfo.cern.ch/asd/geant4/reports/reports.html ] Italian Geant4 web site http:www.ge.infn.it/geant4/ http://wwwinfo.cern.ch/asd/geant4/geant4.html