Electromagnetic physics validation

1. Electromagnetic physicsvalidation Katsuya Amako,Susanna Guatelli, Vladimir Ivanchenko, Michel Maire, Barbara Mascialino, Koichi Murakami, Sandra Parlati, Andreas Pfeiffer, Maria Grazia Pia, Takashi Sasaki, Lazslo Urban Geant4 Workshop Catania, October 4th-9th 2004

2. The project • The project is based on a geographically spread collaboration: INFN Genova INFN Gran Sasso Standard Group KEK THANKS TO KOICHI MURAKAMI, TAKASHI SASAKI, KATSUYA AMAKO FOR THE VERY FRUITFUL COLLABORATION! Preliminary results were presented at last Geant4 Workshop and at IEEE-NSS in Portland. Now the project has reached a mature state.

3. Aim of the project • Project for the validation of all Geant4 electromagnetic models against established references • The project s made-up by two parts: GOODNESS-OF-FIT TESTING PHYSICAL TEST Goodness-of-Fit statistical toolkit Chi-squared stability study test50 Quantitative statistical comparisons allow: - an evaluation of Geant4 physics goodness - how the specific models behave in the same experimental condition POSSIBILITY OF CHOOSING THE MOST APPROPRIATE MODEL

4. First phase: validation against the NIST database Photon Attenuation Coefficient Photon Cross Sections(attenuation coefficients with only one process activated) Electrons CSDA range and Stopping Power (no multiple scattering, no energy fluctuations) Protons CSDA range and Stopping Power (no multiple scattering, no energy fluctuations) Alpha particles CSDA range and Stopping Power (no multiple scattering, no energy fluctuations) Elements: Be, Al, Si, Fe, Ge, Ag, Cs, Au, Pb, U Energy range: 1 keV – 100 GeV Testing activity has been automatised (thanks to SandraParlati and Koichi Murakami)

5. Photons: attenuation coefficient χ2/ν stability study Be Z dependency?

6. Photon attenuation coefficient: statistical results NIST – XCOM LowE Livermore NIST – XCOM LowE Penelope NIST – XCOM Standard

7. Photons: photoelectric cross section χ2/ν stability study Be Cs Z dependency?

8. Photon photoelectric cross section: statistical results NIST – XCOM LowE Livermore NIST – XCOM LowE Penelope NIST – XCOM Standard

9. Photons: Compton cross section The 1keV deviation effect is evident in both LowE Penelope and Standard packages As an example, let us consider Ag:

10. Photon Compton cross section: statistical results NIST – XCOM LowE Livermore NIST – XCOM LowE Penelope NIST – XCOM Standard

11. Compton cross sections χ2/ν stability study (without the E=1 keV point) Ge χ2/ν stability study Si Pb Au

12. Photons: pair production cross section χ2/ν stability study Be (not compatible with the NIST) Beryllium deviations χ2/ν stability study

13. Photon pair production cross section: statistical results NIST – XCOM LowE Livermore NIST – XCOM LowE Penelope NIST – XCOM Standard Removing the 1 keV point

14. Photons: Rayleigh cross section χ2/ν stability study Si Al Au Ge U Pb Fe χ2/ν stability study deviations

15. Photon Rayleigh cross section: statistical results NIST – XCOM LowE Livermore NIST – XCOM LowE Penelope Test results are not consistent

16. Critical discussion of this result • The disagreement between NIST reference data and data coming from the recent library EPDL97 (provided by Lawrence Livermore National Laboratory) within the range of energies between 1 keV and 1 MeV has been already underlined and discussed in a recent paper by Zaidi*. • In his paper Zaidi concluded that EPDL97 is the most up-dated, complete and consistent data library available at the moment. For these features, it should be considered as a standard. * Zaidi H., 2000, Comparative evaluation of photon cross section libraries for materials of interest in PET Monte Carlo simulation IEEE Transaction on Nuclear Science 47 2722-35

17. Electrons: stopping power χ2/ν stability study The three models are equivalent Strange effect (as a function of Z) NIST – ESTAR LowE Livermore BEST FIT χ2/ν = -0.032 + 0.0074 Z R2=0.995 p<0.0001 BEST FIT NIST – ESTAR LowE Penelope χ2/ν = -0.032 + 0.0074 Z R2=0.995 p<0.0001 BEST FIT NIST – ESTAR Standard χ2/ν = -0.046 + 0.0073 Z R2=0.989 p<0.0001

18. Electrons stopping power: statistical results NIST – ESTAR LowE Livermore NIST – ESTAR LowE Penelope NIST – ESTAR Standard

19. Electrons: CSDA range χ2/ν stability study Ag (to be explained) The three models are equivalent

20. Electrons CSDA range: statistical results NIST – ESTAR LowE Livermore NIST – ESTAR LowE Penelope NIST – ESTAR Standard

21. Protons and alpha particles • LowE Ziegler 85 • LowE Ziegler 2000 • ICRU • Standard At low energies: free electron gas model At middle energies (~ MeV): parametrisations At high energies: Bethe Bloch NIST database Statistical comparison cannot lead to a real physics validation, but we can only compare two different models (NIST – Ziegler)

22. Protons: stopping power χ2/ν stability study LowE ICRU Standard LowE Ziegler 85 lOWe Ziegler 2000 NIST - PSTAR

23. Protons stopping power: statistical results NIST – PSTAR LowE Ziegler2000 NIST – PSTAR Standard NIST – PSTAR LowE ICRU49 NIST – PSTAR LowE Ziegler85

24. Protons: CSDA range χ2/ν stability study LowE ICRU Standard LowE Ziegler 85 LowE Ziegler 2000 NIST - PSTAR

25. Protons CSDA range: statistical results NIST – PSTAR LowE Ziegler2000 NIST – PSTAR Standard NIST – PSTAR LowE ICRU49 NIST – PSTAR LowE Ziegler85

26. Alpha particles: stopping powerWORK IN PROGRESS LowE ICRU Standard LowE Ziegler 77 NIST - ASTAR

27. Alpha particles: CSDA rangeWORK IN PROGRESS LowE ICRU Standard LowE Ziegler 77 NIST - ASTAR

28. Statistical comparisons (II) Concerning alpha particles, this is the second iteration of production and analysis since last July. This because thanks to the quantitative analysis we could detect a conceptual flaw in physics tablestreatment for both protons and alpha particles. Systematic data analysis allowed to improve the physical models.

29. SUMMARY: photons and electrons • Low Energy Livermore is the most compatible with the NIST reference (Rayleigh scattering is a special case) • Low Energy Penelope is quite compatible with NIST reference except for some problems exhibited in Compton scattering and pair production cross sections • Standard electrons are compatible with NIST, photons are quite compatible, but exhibit some problems

30. SUMMARY: protons and alpha particles • While NIST represents an established reference for photon and electron processes, the reference for protons and alpha processes in controversial at least in the lower energy ranges. • Two reference data compilations ICRU/NIST and Ziegler. • Quantitative comparisons available for all NIST quantities for protons and alpha particles.

31. Conclusions • Validation of all Geant4 Electromagnetic models against the NIST database • Quantitative statistical analysis on all the comparisons • Fully automated testing system (thanks to Sandra Parlati and Koichi Murakami) • Objective comparison among Geant4 models (with respect to the NIST reference) • Mature project and results will be presented at IEEE-NSS – paper submitted for publication next month

32. Future perspectives • Final states • angular distributions and spectra • The first results will be shown and discussed in the parallel section Physics Book introductory talk by Susanna Guatelli