Simulation capabilities and application results

1. Budker Inst. of Physics IHEP Protvino MEPHI Moscow Pittsburg University Simulation capabilities and application results http://cern.ch/geant4/geant4.html Maria Grazia Pia INFN Genova on behalf of the Geant4 Collaboration EPS-HEP 2001 Conference Budapest, 12-18 July 2001

2. ATLAS BaBar highlights An extensive set of physics processes and models over a wide energy range 192Ir UKDM, Boulby Mine High energy m Low energy photons aparticle in a cell GLAST Budker Inst. of Physics IHEP Protvino MEPHI Moscow Pittsburg University Courtesy of L3 Photon attenuation Courtesy of the Italian Nat. Inst. for Cancer Research E (MeV) A rigorous approach to software engineering

3. Geant4 is a simulation Toolkit designed for a variety of applications It adopts rigorous software engineering methodologies and is based on OO technology It has been developed and is maintained by an international collaboration of > 100 scientists RD44 Collaboration (1994-98) 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 run, event and track management geometry and materials tracking detector response PDG-compliant particle management user interface visualisation persistency physics processes A wide domain of applications with a large user community in many fields HEP, astrophysics, nuclear physics, space sciences, medical physics, radiation studies etc.

4. Geant4 architecture Domain decomposition hierarchical structure of sub-domains Uni-directional flow of dependencies Use of Standards • de jure and de facto Software Engineering plays a fundamental role in Geant4 • formally collected • systematically updated • PSS-05 standard User Requirements Software Process • spiral iterative approach • regular assessments and improvements • monitored following the ISO 15504 model • OOAD • use of CASE tools Object Oriented methods • essential for distributed parallel development • contribute to the transparency of physics • commercial tools • code inspections • automatic checks of coding guidelines • testing procedures at unit and integration level • dedicated testing team Quality Assurance

5. Chandra ATLAS XMM-Newton BaBar Borexino CMS Geometry Role: detailed detector description and efficient navigation Multiple representations (Same abstract interface) • CSG (Constructed Solid Geometries) • - simple solids • STEP extensions • - polyhedra,, spheres, cylinders, cones, toroids, etc. • BREPS(Boundary REPresented Solids) • - volumes defined by boundary surfaces • - include solids defined by NURBS(Non-Uniform Rational B-Splines) CAD exchange: ISO STEP interface Fields: of variable non-uniformity and differentiability External tool for g3tog4 geometry conversion

6. Guidelines for 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.” with attention to UR Geant4 physics keeps evolving facilitated by the OO technology

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

8. Multiple scattering Bremsstrahlung Ionisation Annihilation Photoelectric effect Compton scattering Rayleigh effect g conversion e+e- pair production Synchrotron radiation Transition radiation Cherenkov Refraction Reflection Absorption Scintillation Fluorescence Auger(in progress) High energy extensions needed for LHC experiments, cosmic ray experiments… Low energy extensions fundamental for space and medical applications, n experiments, antimatter spectroscopy etc. Alternative models for the same process energy loss Electromagnetic physics • electrons and positrons • g, X-ray and optical photons • muons • charged hadrons • ions Comparable to Geant3 already in the 1st a release (1997) Further extensions (facilitated by the OO technology) All obeying to the same abstract Process interfacetransparent to tracking

9. Geant4 Geant3 data Standard e.m. processes 1 keV up to O(100 TeV) Multiple scattering 6.56 MeV proton , 92.6 mm Si • Multiple scattering • new model (by L. Urbán) • computes mean free path length and lateral displacement • New energy loss algorithm • optimises the generation of d rays near boundaries • Variety of models for ionisation and energy loss • including the PhotoAbsorption Interaction model • Differential and Integral approach • for ionisation, Bremsstrahlung, positron annihilation, energy loss and multiple scattering J.Vincour and P.Bem Nucl.Instr.Meth. 148. (1978) 399

10. shell effects Low energy e.m. extensions Fundamental for neutrino/dark matter experiments, space and medical applications, antimatter spectroscopy etc. Bragg peak e, down to 250 eV (EGS4, ITS to 1 keV, Geant3 to 10 keV) Hadron and ionmodels based on Ziegler and ICRU data and parameterisations Based on EPDL97, EEDL and EADL evaluated data libraries Barkas effect (charge dependence) models for negative hadrons Photon attenuation ions protons antiprotons

11. Photon entering a light concentrator CTF-Borexino Optical photons Muons • 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) • 1 keV up to 1000 PeV scale • simulation of ultra-high energy and cosmic ray physics • High energy extensions based on theoretical models

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

13. Other models are completely new, such as: Stopping p absorption Neutrons Courtesy of CMS nuclear deexcitation MeV Energy Parameterised and data-driven hadronic models (2) stopping particles: - , K- (relevant for m/p PID detectors) Isotope production neutrons • Allworldwideexisting databases used in neutron transport • Brond, CENDL, EFF, ENDFB, JEF, JENDL, MENDL etc.

14. Discrete transitions from ENSDF data Geant4 Giant Dipole Resonance Theoretical model for continuum Theory-driven models Complementary and alternative models Evaporation phase Low energy range,pre-equilibrium,O(100 MeV) Intermediate energy range, O(100 MeV) to O(5GeV),intra-nuclear transport High energy range, hadronic generator régime

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

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

17. AIDA Courtesy of A. Pfeiffer, CERN Lizard Java Analysis Studio Interface to external tools Through abstract interfaces No dependence  Minimize coupling of components Example: AIDA & Analysis Tools • Similar approach: • graphics • (G)UI • persistency • etc.

18. BaBar Courtesy of D. Wright for the BaBar Collaboration Preliminary

19. Example of integrated Fast/Full Simulation application • BaBar Object-oriented Geant4-based Unified Simulation (BOGUS) • Integrated framework for Fast and Full simulation • Fast simulation available for public use since February 1999 • Integrated in BaBar environment • primary generators, reconstruction, OODB persistency • parameters for materials and geometry shared with reconstruction applications Exploits Geant4 parameterisation (new feature) Courtesy of G. Cosmo for the BaBar Collaboration

20. ATLAS 300 GeV muons 20 GeV pions TRT: Energy loss measured in ATLAS test beam compared to Geant3 and Geant4 simulations (PAI model) Preliminary Liquid Ar calorimeter Fcal energy resolution Muon detector Courtesy of D. Barberis for ATLAS Collaboration

21. HARP with GEANT4 Courtesy of P. Arce for the HARP Collaboration

22. Preliminary T9 beam line Sophisticated geometry Very non-uniform strong magnetic field Primary target as a particle source Crucial to have a precise absolute knowledge of the particle rate incident onto HARP target Beam profile and composition at the HARP target Impossible to separate experimentally p from m in the beam with the accuracy required Courtesy of P. Arce for the HARP Collaboration

23. GLAST GLAST (g-ray telescope) Preliminary Courtesy of F. Longo and R. Giannitrapani, GLAST

24. Cosmic rays, jovian electrons unique simulation capabilities: Courtesy SOHO EIT Solar X-rays, e, p Courtesy of R. Nartallo, ESA X-ray telescope Courtesy of S. Magni, Borexino XMM ZEPLIN III Dark Matter, Boulby mine Courtesy of A. Howard, UKDM Other astroparticle applications Solar system explorations • low E physics • fluorescence • radioactivity • neutrons • space modules • etc..

25. 192Ir Courtesy LIP & Portuguese Oncological Institute data Histogram: Geant4 Commercial treatment planning system anisotropy Technology transfer • Medical applications of Geant4: • radiotherapy • PET • dosimetry • etc. Brachytherapy Treatment planning Courtesy National Inst. for Cancer Research, Genova Isodoses

26. Conclusions • Geant4 is a simulation Toolkit, providing advanced tools for all the domains of detector simulation • Geant4 is characterized by a rigorous approach to software engineering • Thanks to the OO technology, Geant4 is open to extension and evolution • An abundant set of physics processes is available, often with a variety of complementary and alternative physics models • Its areas of application span diverse fields: HEP and nuclear physics, astrophysics and space sciences, medical physics, radiation studies etc.