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Electromagnetic Physics

Budker Inst. of Physics IHEP Protvino MEPHI Moscow Pittsburg University. 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

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Electromagnetic Physics

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  1. Budker Inst. of Physics IHEP Protvino MEPHI Moscow Pittsburg University 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 http://www.cerninfo.cern.ch/asd/geant4/geant4.html MC2000 Conference, Lisbon, 20-23 October 2000

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

  3. 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

  4. Use of Standards • de jure and de facto Geant4 architecture Software Engineering plays a fundamental role in Geant4 • formally collected • systematically updated • PSS-05 standard User Requirements Domain decomposition has led to a hierarchical structure of sub-domains linked by a uni-directional flow of dependencies Software Process • spiral iterative approach • regular assessments and improvements • monitored following the ISO 15504 model • OOAD • use of CASE tools ObjectOriented 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 QualityAssurance

  5. 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 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 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 Features of Geant4 Physics The transparency of the physics implementation contributes to the validation of experimental physics results

  6. 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) Comparable to Geant3 already in the 1st a release (1997) High energy extensions fundamental for LHC experiments, cosmic ray experiments etc. Low energy extensions fundamental for space and medical applications, neutrino experiments, antimatter spectroscopy etc. Alternative models for the same physics process Electromagnetic physics • It handles • electrons and positrons • g, X-ray and optical photons • muons • charged hadrons • ions energy loss

  7. OO design Class diagram of electromagnetic physics Alternative models, obeying the same abstract interface, are provided for the same physics interaction

  8. Standard electromagnetic processes 1 keV up to O(100 TeV) • Photons • Compton scattering • g conversion • photoelectric effect • Electrons and positrons • Bremsstrahlung • ionisation • continuous energy loss from Bremsstrahlung and ionisation • d ray production • positron annihilation • synchrotron radiation • Charged hadrons Shower profile, 1 GeV e- in water J&H Crannel - Phys. Rev. 184-2 August69

  9. Features of Standard e.m. processes Multiple scattering 6.56 MeV proton , 92.6 mm Si • Multiple scattering • new model • 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. Photo Absorption Ionisation Model Ionisation energy loss produced by charged particles in thin layers of absorbers 3 GeV/c p in 1.5 cm Ar+CH4 5 GeV/c p in 20.5 mm Si Ionisation energy loss distribution produced by pions, PAI model

  11. Low energy extensions: e-, g 250 eV up to 100 GeV • Based on EPDL97, EEDL and EADL evaluated data libraries • cross sections • sampling of the final state • Photoelectric effect • Compton scattering • Rayleigh scattering • g conversion • Bremsstrahlung • Ionisation • Fluorescence Photon transmission on 1 mm Al http://www.ge.infn.it/geant4/lowE

  12. water water Photon attenuation coefficient Comparison with NIST data Standard electromagnetic package and Low Energy extensions Fe

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

  14. 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 d ray production • e+e- Pair production

  15. 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

  16. Openness to evolution 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 Lower energy extensions, new models for polarisation, new models for material dependence etc.

  17. User support • User Support is a key feature of Geant4 • Users (experiments, laboratories, institutes) are members of the collaboration itself • User Requirements are formally collected and regularly updated • Extensive documentation available from the web (5 manuals) • 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. • A distributed model of User Support • 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

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

  19. 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

  20. Related presentationsat this conference • V. Grichine Fast Simulation of X-ray Transition Radiation in the Geant4 Toolkit • P. Nieminen Space applications of the Geant4 Toolkit • P. Arce et al. Multiple scattering in Geant4 • S. Chauvie Medical applications of the Geant4 Toolkit http://www.cerninfo.cern.ch/asd/geant4/geant4.html http://www.ge.infn.it/geant4/lowE http://www.ge.infn.it/geant4/dna

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