1. Maria Grazia Pia, INFN Genova Overview of the Object Oriented Simulation Toolkit Maria Grazia Pia INFN Genova, Italy Maria.Grazia.Pia@cern.ch on behalf of the Geant4 Collaboration Budker Inst. of Physics IHEP Protvino MEPHI Moscow Pittsburg University Budker Inst. of Physics IHEP Protvino MEPHI Moscow Pittsburg University

2. Maria Grazia Pia, INFN Genova The role of simulation l design l design of the experimental set-up physics output l evaluation and definition of the potential physics output of the project risks l evaluation of potential risks to the project performance l assessment of the performance of the experiment reconstruction analysis software l development, test and optimisation of reconstruction and physics analysis software physics results l contribution to the calculation and validation of physics results  The scope of Geant4 encompasses the simulation of the passage of particles through matter l there are other kinds of simulation components, such as physics event generators, detector/electronics response generators, etc. l often the simulation of a complex experiment consists of several of these components interfaced to one another Simulation plays a fundamental role in various domains and phases of an experimental physics project

3. Maria Grazia Pia, INFN Genova EGS4, EGS5, EGSnrc MCNP, MCNPX, A3MCNP, MCNP-DSP, MCNP4B Penelope Geant3, Geant4 Tripoli-3, Tripoli-3 A, Tripoli-4 Peregrine MVP, MVP-BURN MARS MCU MORSE TRAX MONK MCBEND VMC++ LAHET RTS&T-2000 NMTC HERMES FLUKA EA-MC DPM SCALE GEM MF3D...and I probably forgot some more Many codes not publicly distributed A lot of business around MC The zoo Monte Carlo codes presented at the MC200 Conference, Lisbon, October 2000

4. Maria Grazia Pia, INFN Genova Integrated suites vs specialised codes Pro: the specific issue is treated in great detail sometimes the package is based on a wealth of specific experimental data simple code, usually relatively easy to install and use Contra: a typical experiment covers many domains, not just one domains are often inter-connected Pro: the same environment provides all the functionality Contra: it is more difficult to ensure detailed coverage of all the components at the same high quality level monolithic: take all or nothing limited or no options for alternative models usually complex to install and use difficult maintenance and evolution Specialised packages cover a specific simulation domain Integrated packages cover all/many simulation domains

5. Maria Grazia Pia, INFN Genova The Toolkit approach A toolkit is a set of compatible components l each component is specialised for a specific functionality l each component can be refined independently to a great detail l components can be integrated at any degree of complexity l components can work together to handle inter-connected domains l it is easy to provide (and use) alternative components l the simulation application can be customised by the user according to his/her needs l maintenance and evolution - both of the components and of the user application - is greatly facilitated...but what is the price to pay? l the user is invested of a greater responsibility l he/she must critically evaluate and decide what he/she needs and wants to use

6. Maria Grazia Pia, INFN Genova Geant 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 The Geant approach

7. Maria Grazia Pia, INFN Genova  Geant4 is a simulation Toolkit designed for a variety of applications  It has been developed and is maintained by an international collaboration of > 100 scientists RD44 Collaboration Geant4 Collaboration  The code is publicly distributed from the WWW, together with ample documentation  1st production release: end 1998 2 new releases/year since then  It provides a complete set of tools for all the typical domains of simulation geometry and materials tracking detector response run, event and track management PDG-compliant particle management visualisation user interface persistency physics processes  It is also complemented by specific modules for space science applications

8. Maria Grazia Pia, INFN Genova Geant4 Collaboration n Atlas, BaBar, CMS, HARP, LHCB n CERN, JNL,KEK, SLAC, TRIUMF n Barcelona Univ., ESA, Frankfurt Univ.,Helsinki Univ. IGD, IN2P3, Karolinska Inst., Lebedev, TERA n COMMON (Serpukov, Novosibirsk, Pittsburg etc.) ] 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

9. Maria Grazia Pia, INFN Genova Software Engineering plays a fundamental role in Geant4 User 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 Domain decomposition has led to a hierarchical structure of sub-domains linked by a uni- directional flow of dependencies Geant4 architecture

10. Maria Grazia Pia, INFN Genova Standards Units Geant4 is independent from the system of units all numerical quantities expressed with their units explicitly user not constrained to use any specific system of units Geant4 adopts 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)?

11. Maria Grazia Pia, INFN Genova Data libraries ] Systematic collection and evaluation of experimental data from many sources worldwide  Databases l ENDF/B, JENDL, FENDL, CENDL, ENSDF,JEF, BROND, EFF, MENDL, IRDF, SAID, EPDL, EEDL, EADL, SANDIA, ICRU etc.  Collaborating distribution centres l 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

12. Maria Grazia Pia, INFN Genova 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

13. Maria Grazia Pia, INFN Genova The kernel Run and event l the RunManager can handle multiple events èpossibility to handle the pile-up l multiple runs in the same job èwith different geometries, materials etc. l powerful stacking mechanism èthree 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

14. Maria Grazia Pia, INFN Genova Geometry Multiple representations CSG (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) 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 External tool for g3tog4 geometry conversion

15. Maria Grazia Pia, INFN Genova 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

16. Maria Grazia Pia, INFN Genova 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

17. Maria Grazia Pia, INFN Genova 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.”

18. Maria Grazia Pia, INFN Genova Features of Geant4 Physics  OOD allows to implement or modify any physics process without changing other parts of the software  open to extension and evolution  Tracking  Tracking is independent from the physics processes final state  The generation of the final state is independent from the access and use of cross sections  Transparent access via virtual functions to cross sections (formulae, data sets etc.) models underlying physics processes electromagnetic hadronic  An abundant set of electromagnetic and hadronic physics processes physics models  a variety of complementary and alternative physics models for most processes evaluated databases  Use of public evaluated databases production thresholds  No tracking cuts, only production thresholds range thresholds for producing secondaries are expressed in range, universal for all media converted into energy for each particle and material The transparency of the physics implementation contributes to the validation of experimental physics results

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

20. Maria Grazia Pia, INFN Genova 3 multiple scattering 3 Bremsstrahlung 3 ionisation 3 annihilation 3 photoelectric effect 3 Compton scattering 3 Rayleigh effect   conversion 3 e + e - pair production 3 synchrotron radiation 3 transition radiation 3 Cherenkov 3 refraction 3 reflection 3 absorption 3 scintillation 3 fluorescence 3 Auger (in progress) Electromagnetic physics Comparable to Geant3 already in the 1st  release (1997)  High energy extensions l fundamental for LHC experiments, cosmic ray experiments etc.  Low energy extensions l fundamental for space and medical applications, neutrino experiments, antimatter spectroscopy etc.  Alternative models for the same physics process energy loss It handles electrons and positrons , X-ray and optical photons muons charged hadrons ions

21. Maria Grazia Pia, INFN Genova PAI model Ionisation energy loss distribution produced by pions, PAI model 3 GeV/c  in 1.5 cm Ar+CH45 GeV/c  in 20.5  m Si Photo Absorption Ionisation Model Ionisation energy loss produced by charged particles in thin layers of absorbers

22. Maria Grazia Pia, INFN Genova Muon processes ] Validity range 1 keV up to 10 PeV scale  simulation of ultra-high energy and cosmic ray physics ] High energy extensions based on theoretical models ] Bremsstrahlung  Ionisation and  ray production ] e + e - Pair production

23. Maria Grazia Pia, INFN Genova Processes for optical photons  Optical photon  its wavelength is much greater than the typical atomic spacing  Production of optical photons in HEP detectors is mainly due to Cherenkov effect and scintillation  Processes in Geant4 in-flight absorption Rayleigh scattering medium-boundary interactions (reflection, refraction) Track of a photon entering a light concentrator CTF-Borexino

24. Maria Grazia Pia, INFN Genova Hadronic physics Relevant features l theory-driven, parameterisation-driven, data-driven models l complementary and alternative models Cross section data sets l transparent and interchangeable Final state calculation l models by particle, energy, material

25. Maria Grazia Pia, INFN Genova 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

26. Maria Grazia Pia, INFN Genova 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.

27. Maria Grazia Pia, INFN Genova 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

28. Maria Grazia Pia, INFN Genova A sample from theory-driven models

29. Maria Grazia Pia, INFN Genova 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++

30. Maria Grazia Pia, INFN Genova 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 Modules for space applications Low-energy e.m. extensions

31. Maria Grazia Pia, INFN Genova 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

32. Maria Grazia Pia, INFN Genova 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)

33. Maria Grazia Pia, INFN Genova Documentation User Documentation l Introduction to Geant4 l Installation Guide l Application Developer Guide l Toolkit Developer Guide l Software Reference Manual l Physics Reference Manual 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://cern.ch/geant4/reports/gallery/ Publication and Results web page http://cern.ch/geant4/reports/reports.html Low Energy e.m. Physics http:www.ge.infn.it/geant4/lowE http://cern.ch/geant4/geant4.html Seminars and Training courses available

34. Maria Grazia Pia, INFN Genova 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

35. Maria Grazia Pia, INFN Genova Geant4 review ] Next week at CERN ] External review to evaluate Geant4 activity in 1999-2000 ] Chairman: U. Mortensen (ESA) ] Part 1 l Presentation of the activity of Geant4 Collaboration in 1999-2000 (functionalities, user support etc.) ] Part 2 l Results of applications from user groups (mainly comparisons with data) l Feedback on user support ] Not a channel to present user requirements l User requirements should be conveyed through the normal User Support path (TSB Representatives) l TSB Representatives attending this Round Table: l V. Ivanchenko (Novosibirsk, Common), P. Nieminen (ESA), M.G. Pia (INFN), P. Truscott (DERA)