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Geant4 Electromagnetic Physics Progress

This document outlines the actions carried out by Geant4 Electromagnetic (EM) groups from January 2008 to January 2009, including low-energy group reorganization, software infrastructure update, and documentation update. The Standard EM group and recent activities are also discussed, along with plans for 2009 and beyond. The document includes responses to review recommendations and concludes with remarks on the outlook for 2010-2012.

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Geant4 Electromagnetic Physics Progress

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  1. Geant4 Electromagnetic Physics Progress S.Incerti and V.Ivanchenko for Geant4 electromagnetic groups 20 January 2008 20 January 2009

  2. Outline • Actions carried out by Geant4 EM groups to address 2007 review recommendations • Low-energy group reorganization • Software infrastructure update • Documentation update • Standard EM group • Recent activity • Plan for 2009 and beyond • Responses to review recommendations #1-#5 • Conclusion remarks 20 January 2009

  3. Low-energy group reorganization • S.Incerti was elected as a working group coordinator in spring 2008 • Low-energy working group have been reorganized with main goals: • To increase manpower and efficiency of the group • To enable more active participation of experts in low-energy EM projects • To extend capability of the sub-package • Details see in the talk of S.Incerti 20 January 2009

  4. Software infrastructure update • To provide the most effective usage of Standard and Low-energy EM models a number of improvements have been already introduced in EM software infrastructure • Common interfaces were updated in view of potential combination of standard and low-energy models • Physics Lists configuration • Low-energy group started migration to common model based interface in 2008 • It is planned to complete in first part of 2009 20 January 2009

  5. Documentation update • The electromagnetic web pages have been completely reorganized: • EM Home page easily accessible from G4 web http://geant4.web.cern.ch/geant4/collaboration/EMindex.shtml • EM TWiki pages have been created (C.Zacharatou) https://twiki.cern.ch/twiki/bin/view/Geant4/ElectromagneticPhysics • Pages are maintained by common efforts of both EM groups 20 January 2009

  6. Electromagnetic (Standard) working group 20 January 2009

  7. Electromagnetic (Standard) working group • Exist since beginning of Geant4 • Leader for many years - Michel Maire • Web: http://geant4.web.cern.ch/geant4/collaboration/working_groups/electromagnetic/index.shtml • Main focused on LHC • Scope of application much wider • Other HEP experiments • Space studies • Medical applications • Instrumental applications 20 January 2009

  8. New physics provided with g4 9.2 • Relativistic bremsstrahlung model for E > 1 GeV • Updated density effect • Hadron induced bremsstrahlung and e+e- pair production processes/models • ICRU’73 data are included and are used for ion ionisation • Multiple scattering (MSC) is specialized per particle type: • Optimization CPU versus precision per particle type • G4eMultipleScatteringprocess with MSC model tuned to e- data (L.Urban) • G4MuMultipleScacttering process for muons and hadrons • Updated positron annihilation to hadrons (rare high energy process) • added ω(782) and φ(1020) contributions • G4Cerenkov process updated • G4Scintillation process includes Birks law 20 January 2009

  9. New options and infrastructure components provided with g4 9.2 • Spline option for physics tables • Option3 Standard Physics builder • Optimized for medical and space applications • New utility classes: • G4EmSaturation – Birks effect (used in G4Scintillation) • NIEL and gamma interactions • G4ElectronIonPair – helper class to sample of ionisation clusters at charged particle step using ICRU’31 approach • G4EmProcessSubType – enumerator of EM processes • G4EmConfigurator – helper class to configure EM models per energy range and G4Region 20 January 2009

  10. Plan for 2009 • Detailed plan is available in the web http://geant4.web.cern.ch/geant4/collaboration/working_groups/electromagnetic/plan2009.txt • Selected millstones for 2009 • Infrastructure upgrade: • Common Standard/Low-energy Physics Lists • “ApplyCuts” options per region (kill secondaries below threshold) • General ion charge exchange process • Cut per recoil • Extend testing suites • Add common validation with LE group • Review of bremsstrahlung and photon processes • Comparison Standard/Livermore/Penelope models • Validation versus data • Further development of ionisation models • Review on ionisation potentials • Introduce new ICRU’73 model to reference Physics Lists • Further development of single and multiple scattering models 20 January 2009

  11. Outlook beyond – plan for 2010-2012 • Complete review of EM cross sections and stopping powers • Theory overview • Comparison of various databases data • Evaluated data and original publications • Introduce the most precise cross sections in both Standard and Low-energy models • Complete single and multiple scattering model review • Optimize configuration of models per particle type and use-case • Extend upper applicability limits by including ultra-relativistic models • Radiative corrections, LPM effect • X-ray production models and optical models development • Polarization model development • Providing Physics Lists components per use-case 20 January 2009

  12. Resources available • 15 members of the working group Geant4 members • 4 associates – model developers • Total manpower 2008 – 6 FTE (highest value) • Estimated manpower 2009 – 5.5 FTE • Experts of underlying theories (in particular QED) – 5 (1.9 FTE) • Model developers – 5 (2.75 FTE) • Only validation so far – 5 (0.85 FTE) • Major support of group members by HEP institutions: • CERN, DESY Zeuthen, KEK, LAPP IN2P3, Lebedev Physics Institute, TRIUMF • We need: • Keep expertise in theory and modeling • Extend expertise for new physics models • Increase validation efforts • Collaboration with other Geant4 groups (Low-energy, Geometry ….) 20 January 2009

  13. Responses to review recommendations 20 January 2009

  14. Recommendation 1 • We recommend setting up an easily accessible central repository with detailed referencestodata comparisons and validation papers for the models, e.g. a web page linked from the EM home page • Geant4 response: • Central repository – main EM TWiki pagehttps://twiki.cern.ch/twiki/bin/view/Geant4/EMValidation • Includes link to the TWiki EM publication page • Links to all available publications of Geant4 concerning EM physics • Links to user publications • Includes links to different validation sub-pages • Most important validation results • EM tests, validation and verification • Web pages are maintained by common efforts of both EM groups 20 January 2009

  15. Recommendation 2 • We recommend rapid integration of the ICRU 73 heavy ion stopping power model • Geant4 response: • During 2008 ICRU’73 data were converted to C++ code and included in G4 material sub-package • Data can be used in concrete models and for validation • The new model for simulation of ion ionisation fully based on ICRU’73 data have been developed by A. Lechner and released with g4 9.2. • Validation is in progress. • Complete validation and usage in referenced Physics Lists will be provided in 2009 20 January 2009

  16. A.Lechner, V.Ivanchenko, (Poster at IEEE NSS 2008) • New model was compared with existing G4 model • Validations have been done for stopping powers and Bragg peak simulation • New model show good robustness • The difference between SRIM, MSTAR, ICRU’73 models was confirmed 20 January 2009

  17. Recommendation 3 • We recommend providing guidance on the tradeoffs between physics accuracy and computing speed. For example, collect and publish via the web results from users in various domains regarding computing speed vs range cut, and provide a Wiki-like forum where users can document their experience; etc • Geant4 response: • Corresponding documentation is provided and is progressively updated with EM web pageshttps://twiki.cern.ch/twiki/bin/view/Geant4/EMValidation • With g4 9.2 different EM Physics Lists are provided variants of EM physics configurations • Reference Physics Lists • Extended and advance examples.  • The trade off is discussed in Geant4 publications, conference presentations, tutorials, HyperNews Forum, and user publications • Permanent efforts • Is a part of the 2009 - 2012 Geant4 working plan 20 January 2009

  18. LHCb type sampling calorimeter: example of tradeoff accuracy versus CPU Optimal working point Accuracy of visible energy depends on cut EMV Physics List underestimates visible energy 20 January 2009

  19. Recommendation 4 • We recommend providing guidance on the choice between the two EM models for specific particle species, energies, etc • Geant4 response: • Corresponding documentation is provided and is progressively updated in Geant4 web https://twiki.cern.ch/twiki/bin/view/Geant4/Geant4PerformanceTips • Common interface for both sub-packages allows more effective way of combining and validation of different EM models • 2008: start the migration to the common model-type interface for EM • 2009 working plan: • Comparisons of Standard, Livermore and Penelope models • Documentation of possible choice 20 January 2009

  20. Example: Gamma conversion • Standard and low-energy models are nearly identical • Compton scattering and photo-electric effects are not identical (see talk of S.Incerti) • As a result of validation and comparison several choices of EM physics will be provided Escape test 20 January 2009

  21. Recommendation 5 • We recommend integrating the two EM models into a single package, similar to what exists in hadronic models. This will allow a user to choose one model in one energy range and the other model in a different energy range in order to optimize physics and computing performance for his application • Geant4 response: • Ongoing convergence of the EM physics • Existing model interface was agreed (and revised slightly) • Different models of the same process may be configured per particle type, per energy range and geometry region • Unification of four EM models (Standard, Livermore, Penelope and DNA) • Low-energy photon processes were migrated to the new interface for g4 9.2 • New ion ionization model was created using common interface • Plans for 2009 and beyond: • Remaining processes/models (Livermore, Penelope, DNA) migration • Validation of migrated processes 20 January 2009

  22. Conclusion remarks • The recommendations #1-#5 are in a good part implemented • There is a plan for 2009 and beyond for completion • The speed of implementation depends on available manpower • Some further details concerning implementations of the recommendations are in next talks 20 January 2009

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