EM physics progress 20 January 2009 1

Geant4 Electromagnetic Physics Progress

S.Incerti and V.Ivanchenko for Geant4 electromagnetic groups

20 January 2008

EM physics progress 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

EM physics progress 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

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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

EM physics progress 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

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Electromagnetic (Standard) working group

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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

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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 G4eMultipleScattering process 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

EM physics progress 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

EM physics progress 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

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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

EM physics progress 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 ….)

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Responses to review recommendations

EM physics progress 20 January 2009 14

Recommendation 1 We recommend setting up an easily accessible central repository

with detailed references to data 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 page

https://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

EM physics progress 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

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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

EM physics progress 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 pages https://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

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LHCb type sampling calorimeter: example of tradeoff accuracy versus CPU

Accuracy of visible energy depends on cut

EMV Physics List underestimates visible energy

Optimal working point

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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

EM physics progress 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

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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

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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