Maria Grazia Pia, CERN/IT and INFN Genova Electromagnetic Physics Maria Grazia Pia CERN/IT and INFN Genova S. Chauvie, V. Grichine, P. Gumplinger, V. Ivanchenko, R. Kokoulin, S. Magni, M. Maire, P. Nieminen, M.G. Pia, A. Rybin, L. Urban on behalf of the Geant4 Collaboration Budker Inst. of Physics IHEP Protvino MEPHI Moscow Pittsburg University MC2000 Conference MC2000 Conference, Lisbon, October

Maria Grazia Pia, CERN/IT and INFN Genova Borexino at Gran Sasso Laboratory Highlights Budker Inst. of Physics IHEP Protvino MEPHI Moscow Pittsburg University Gamma-ray Large Area Space Telescope ATLAS at LHC, CERN CMS at LHC, CERN BaBar at SLAC XMM X-ray telescope A wide domain of applications with a large user community in many fields HEP, astrophysics, nuclear physics, space sciences, medical physics, radiation studies etc. A rigorous approach to software engineering Courtesy of L3 Courtesy of the Italian Nat. Inst. for Cancer Research E (MeV) Photon attenuation An extensive set of physics processes and models over a wide energy range High energy  Low energy photons GLAST

Maria Grazia Pia, CERN/IT and 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 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

Maria Grazia Pia, CERN/IT and 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 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

Maria Grazia Pia, CERN/IT and 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

Maria Grazia Pia, CERN/IT and 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

Maria Grazia Pia, CERN/IT and INFN Genova OO design Alternative models, obeying the same abstract interface, are provided for the same physics interaction Class diagram of electromagnetic physics

Maria Grazia Pia, CERN/IT and INFN Genova Standard electromagnetic processes  Photons l Compton scattering  conversion l photoelectric effect  Electrons and positrons l Bremsstrahlung l ionisation n continuous energy loss from Bremsstrahlung and ionisation  ray production l positron annihilation l synchrotron radiation  Charged hadrons Shower profile, 1 GeV e - in water J&H Crannel - Phys. Rev August69 1 keV up to O(100 TeV)

Maria Grazia Pia, CERN/IT and INFN Genova Features of Standard e.m. processes  Multiple scattering l new model l computes mean free path length and lateral displacement  New energy loss algorithm optimises the generation of  rays near boundaries  Variety of models  Variety of models for ionisation and energy loss l including the PhotoAbsorption Interaction model  Differential and Integral approach l for ionisation, Bremsstrahlung, positron annihilation, energy loss and multiple scattering Multiple scattering 6.56 MeV proton, 92.6 mm Si J.Vincour and P.Bem Nucl.Instr.Meth (1978) 399

Maria Grazia Pia, CERN/IT and INFN Genova PAI model Ionisation energy loss distribution produced by pions, PAI model 3 GeV/c  in 1.5 cm Ar+CH4 5 GeV/c  in 20.5  m Si Photo Absorption Ionisation Model Ionisation energy loss produced by charged particles in thin layers of absorbers

Maria Grazia Pia, CERN/IT and INFN Genova Low energy extensions: e -,  ] Based on EPDL97, EEDL and EADL evaluated data libraries l cross sections l sampling of the final state ] Photoelectric effect ] Compton scattering ] Rayleigh scattering   conversion ] Bremsstrahlung ] Ionisation ] Fluorescence 250 eV up to 100 GeV Photon transmission on 1  m Al

Maria Grazia Pia, CERN/IT and INFN Genova Photon attenuation coefficient Comparison with NIST data Standard Standard electromagnetic package Low Energy and Low Energy extensions Fe water

Maria Grazia Pia, CERN/IT and INFN Genova Low energy extensions: hadrons and ions ] E > 2 MeV  Bethe-Bloch ] 1 keV < E < 2 MeV  parameterisations l Ziegler 1977, 1985 l ICRU 1993 l corrections due to chemical formulae of materials l nuclear stopping power ] E < 1 keV  free electron gas model ] Barkas effect taken into account down to 50 keV l quantum harmonic oscillator model Various models, depending on the energy range and charge

Maria Grazia Pia, CERN/IT and 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

Maria Grazia Pia, CERN/IT and 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

Maria Grazia Pia, CERN/IT and INFN Genova Openness to evolution From the Minutes of LCB (LHCC Computing Board) meeting on 21 October, 1997: Geant4 physics keeps evolving with attention to UR facilitated by the OO technology Lower energy extensions, new models for polarisation, new models for material dependence etc. “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.”

Maria Grazia Pia, CERN/IT and INFN Genova User support ] User Support is a key feature of Geant4 ] Users (experiments, laboratories, institutes) are members of the collaboration itself ] User Requirements ] User Requirements are formally collected and regularly updated documentation ] Extensive documentation available from the web (5 manuals) Training Programme ] A Geant4 Training Programme in preparation ] User Support through a web interface for code-related problem reports ] User Support through human interface for consultancy, investigation of anomalous results etc. distributed model ] A distributed model of User Support l a large number of experts performs the support on the domain of their competence The close relationship with user communities and their feedback is very valuable to Geant4

Maria Grazia Pia, CERN/IT and INFN Genova Geant4 electromagnetic physics Working Groups u M. Maire (LAPP) u P. Nieminen (ESA) u M.G. Pia (INFN Genova) u S. Agostinelli - (IST Genova) u P. Andreo (Karolinska Inst.) u D. Belkic (Karolinska Inst.) u A. Brahme (Karolinska Inst.) u A. Carlsson (Karolinska Inst.) u G. Cabras (INFN Udine) u S. Chauvie (INFN Torino) u G. Depaola (Univ. Cordova) u R. Cirami (INFN Trieste) u E. Daly (ESA) u A. De Angelis (INFN Udine) u G. Fedel (INFN Trieste) u J.M. Fernandez Varea (Univ. Barcelona) u S. Garelli (IST Genova) u R. Giannitrapani (INFN Udine) u V. Grichine (LPI Moscow) u I. Gudowska (Karolinska Inst.) u P. Gumplinger (TRIUMF) u V. Ivanchenko (Budker Institute ) u R. Kokouline (MEPhI, Moscow) u E. Lamanna (INFN Cosenza) u S. Larsson (Karolinska Inst.) u R. Lewensohn (Karolinska Inst.) u B.K. Lind (Karolinska Inst.) u J. Lof (Karolinska Inst.) u F. Longo (INFN Trieste) u B. De Lotto (INFN Udine) u F. Marchetto (INFN Torino) u E. Milotti (INFN Udine) u R. Nartallo (ESA) u G. Nicco (Univ. Torino) u B. Nilsson (Karolinska Inst.) u V. Rolando (Univ. Piemonte Orient.) u A. Rybin (IHEP Protvino) u G. Santin (INFN Trieste) u U. Skoglund (Karolinska Inst.) u A. Solano (INFN Torino) u R. Svensson (Karolinska Inst.) u N. Tilly (Karolinska Inst.) u L. Urban (KFKI Budapest) Standard e.m. Physics Low Energy Low Energy e.m. Physics

Maria Grazia Pia, CERN/IT and INFN Genova Conclusions ] Geant4 is a simulation Toolkit, providing advanced tools for all the domains of detector simulation ] Its areas of application span diverse fields: HEP and nuclear physics, astrophysics and space sciences, medical physics, radiation studies etc. ] Geant4 is characterized by a rigorous approach to software engineering ] Geant4 electromagnetic physics covers a wide energy range of interactions of electrons and positrons, photons, muons, charged hadrons and ions ] An abundant set of electromagnetic physics processes is available, often with a variety of complementary and alternative physics models ] Low and high energy extensions have opened new domains of applications ] Thanks to the OO technology, Geant4 is open to extension and evolution

Maria Grazia Pia, CERN/IT and INFN Genova Related presentations at this conference ] V. GrichineFast Simulation of X-ray Transition Radiation in the Geant4 Toolkit ] P. NieminenSpace applications of the Geant4 Toolkit ] P. Arce et al.Multiple scattering in Geant4 ] S. ChauvieMedical applications of the Geant4 Toolkit