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 IEEE - NSS Rome, October 2004

2. - Evaluation of Geant4 physics goodness • How the various Geant4 models behave in the same experimental condition • - Systematic data analysis allows to improve the physics models and guarantees the reliability Scope Aim of the project • Validation of Geant4 electromagnetic models against established references (ICRU - NIST) • Simulation of physics quantities in the same experimental set-up as reference data • Rigorous quantitative statistical comparison Quantitative statistical analysis PHYSICAL TEST GOODNESS-OF-FIT TESTING

3. Alternative models for the same physics process High energy models fundamental for LHC experiments, cosmic ray experiments etc. Low energy models fundamental for space and medical applications, neutrino experiments, antimatter spectroscopy etc. two “flavours” of models: model based on Livermore libraries à la Penelope multiple scattering bremsstrahlung ionisation annihilation photoelectric effect Compton scattering Rayleigh effect gamma conversion e+e- pair production synchrotron radiation transition radiation Cherenkov refraction reflection absorption scintillation fluorescence Auger It handles electrons and positrons, gamma, X-ray and optical photons, muons, charged hadrons, ions Geant4 Electromagnetic Physics models Standard Package Geant4 Electromagnetic Package LowEnergy Package Muon Package Optical photon Package

4. Physics quantities under study • Photon Attenuation Coefficient • Photon Cross Sections(attenuation coefficients with only one process activated) • ElectronCSDA range and Stopping Power (no multiple scattering, no energy fluctuations) • ProtonCSDA range and Stopping Power (no multiple scattering, no energy fluctuations) • AlphaCSDA range and Stopping Power (no multiple scattering, no energy fluctuations) Elements: Be, Al, Si, Fe, Ge, Ag, Cs, Au, Pb, U + water Energy range: 1 keV – 10 GeV Testing activity has been automatised (INFN Gran Sasso Laboratory and KEK)

5. p < 0.05: Geant4 simulations and NIST data differ significantly p > 0.05: Geant4 simulations and NIST data do not differ significantly The p-value represents the probability that the test statistics has a value at least as extreme as that observed, assuming the null hypothesis is true 0 ≤ p ≤ 1 Statistical analysis • The statistical analysis has been performed by means of a Goodness-of-Fit Statistical Toolkit • The two hypothesis under study are the following: • H0: Geant4 simulations = NIST data • H1: Geant4 simulations ≠ NIST data Distance between Geant4 simulations and NIST reference data GoF Toolkit GoF test (χ2 test) Test result (p-value)

6. Physics models under test: • Geant4 Standard • Geant4 Low Energy – EPDL • Geant4 Low Energy – Penelope • Reference data: • NIST - XCOM p-value stability study Transmitted photons (I) Photon beam (Io) p-value H0 ACCEPTANCE AREA H0 REJECTION AREA Z Photon attenuation coefficient Experimental set-up Geant4 LowE Penelope Geant4 Standard Geant4 LowE EPDL NIST - XCOM • The three Geant4 models reproduce total attenuation coefficients with high accuracy • The two Geant4 LowE models exhibit the best agreement

7. Physics models under test: • Geant4 Standard • Geant4 Low Energy – EPDL • Geant4 Low Energy – Penelope • Reference data: • NIST - XCOM p-value H0 REJECTION AREA Z Photoelectric cross section • The three Geant4 models reproduce photoelectric cross sections with high accuracy • The two Geant4 LowE models exhibit the best agreement p-value stability study Geant4 LowE Penelope Geant4 Standard Geant4 LowE EPDL NIST - XCOM Geant4 LowE Penelope Geant4 Standard Geant4 LowE EPDL

8. Compton scattering cross section • Physics models under test: • Geant4 Standard • Geant4 Low Energy – EPDL • Geant4 Low Energy – Penelope • Reference data: • NIST - XCOM p-value stability study Geant4 LowE Penelope Geant4 Standard Geant4 LowE EPDL p-value H0 REJECTION AREA Z • The three Geant4 models reproduce Compton scattering cross sections with high accuracy • The Geant4 LowE – EPDL model exhibits the best agreement Geant4 LowE Penelope Geant4 Standard Geant4 LowE EPDL NIST - XCOM

9. Pair production cross section • Physics models under test: • Geant4 Standard • Geant4 Low Energy – EPDL • Geant4 Low Energy – Penelope • Reference data: • NIST - XCOM p-value H0 REJECTION AREA • The three Geant4 models reproduce pair production cross sections with high accuracy • The Geant4 LowE – EPDL model exhibits the best agreement p-value stability study Geant4 LowE Penelope Geant4 Standard Geant4 LowE EPDL Geant4 LowE Penelope Geant4 Standard Geant4 LowE EPDL NIST - XCOM Z

10. Physics models under test: • Geant4 Standard • Geant4 Low Energy – EPDL • Geant4 Low Energy – Penelope • Reference data: • NIST - XCOM Geant4 Penelope Geant4 LowE EPDL p-value H0 REJECTION AREA Rayleigh scattering cross section The Geant4 models seem to be in disagreement with the reference data p-value stability study Geant4 Penelope Geant4 LowE EPDL NIST - XCOM Z

11. Rayleigh scattering cross section • The NIST database and the EPDL97 evaluated data library give Rayleigh cross section data in disagreement for E < 1 MeV • EPDL97 is the most up-to- date, complete and consistent data library available at the moment (Zaidi, 2000). NIST EPDL 97 * 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

12. Electron Stopping Power • Physics models under test: • Geant4 Standard • Geant4 Low Energy – Livermore • Geant4 Low Energy – Penelope • Reference data: • NIST ESTAR - ICRU 37 Experimental set-up centre p-value stability study Geant4 LowE Penelope Geant4 Standard Geant4 LowE EEDL NIST - XCOM p-value Geant4 LowE Penelope Geant4 Standard Geant4 LowE EEDL The three Geant4 models are equivalent H0 REJECTION AREA Z

13. Physics models under test: • Geant4 Standard • Geant4 Low Energy – Livermore • Geant4 Low Energy – Penelope • Reference data: • NIST ESTAR - ICRU 37 p-value H0 REJECTION AREA Electron CSDA Range CSDA range: particle range without energy loss fluctuations and multiple scattering p-value stability study Geant4 LowE Penelope Geant4 Standard Geant4 LowE EEDL NIST - XCOM Geant4 LowE Penelope Geant4 Standard Geant4 LowE EEDL The three Geant4 models are equivalent Z

14. Protons Alpha particles • Geant4 models under test: • Geant4 models under test: • Standard • Low Energy – ICRU 49 • Low Energy – Ziegler 85 • Low Energy – Ziegler 2000 • Standard • Low Energy – ICRU 49 • Low Energy – Ziegler 77 • Reference data: • Reference data: NIST PSTAR – ICRU 49 NIST ASTAR – ICRU 49 Protons and alpha particles • Comparison of Geant4 models with respect to ICRU 49 protocol • Geant4 LowE Package has ICRU 49 parameterisations as one of its models verification, not validation • The Ziegler parameterisations are as authoritative as the ICRU 49 reference • comparison rather than validation

15. Stopping Power and CSDA Range Proton stopping power Proton CSDA range Geant4 LowE ICRU Geant4 Standard Geant4 LowE Ziegler 85 Geant4 LOWe Ziegler 2000 NIST PSTAR - ICRU 49 p>0.05 Geant4 LowE ICRU Geant4 Standard Geant4 LowE Ziegler 85 Geant4 LOWe Ziegler 2000 NIST PSTAR - ICRU 49 Geant4 LowE ICRU Geant4 Standard Geant4 LowE Ziegler 85 Geant4 LOWe Ziegler 2000 NIST PSTAR - ICRU 49 p>0.05 Similar results for alpha particles

16. Conclusions • Systematic validationof Geant4 electromagnetic models against ICRU protocols and NIST reference data • Validation based on arigorous, quantitative statistical analysis of test results • All Geant4 electromagnetic models are in agreement with the reference data • The Geant4 Low Energy Package is the most accurate with respect to the ICRU protocol • More results: http://www.ge.infn.it/geant4/analysis/book • Future: extend the validation test to other physics quantities