1. 1 Status and Plans for Geant4 Physics Linear Collider Simulation Workshop III 2-5 June 2004 Dennis Wright (SLAC)

2. 1 Outline Electromagnetic Physics – status and plans – validation plots Hadronic Physics – status and plans – validation plots

3. 1 Electromagnetic Physics: Model Approach ●Current status: – ionization, bremsstrahlung, multiple scattering are coupled due to reliance on pre-calculated energy loss tables ●Goal: – de-couple them by abstracting common behavior – allow multiple physics models to be applied to each process – allow models to be defined for given geometric region or energy ●Example: – can choose G4MollerBhabhaModel for energy loss and production of deltas by e+/e- – Or G4PAIModel for delta production by heavy charged particles

4. 1 Electromagnetic Physics: Multiple Scattering ●Migration to Model Approach was to have been transparent to user, but bugs were introduced in Geant4 6.0 ●width of angular distribution in MS became too large by 30% ● only muons and hadrons were affected ● electrons OK ●other bugs as well: ● mu ionization cross section 10% too small ● infinite loop for particles stopping in very low density gas ●Problems fixed by Geant4 6.1 => don't use 6.0!

5. 1 Electromagnetic Physics: Multiple Scattering ●New features: ●improved transformation between geometric and true path length ●use Highland formula for Gaussian part of angular distribution for electrons ●option to allow backscattering at boundaries ●Plans: ●Develop MS processes which are specific to muons and ions

6. 1 Electromagnetic Physics: Other Processes ●Mu ionization – addition of radiative corrections for energies above 1 GeV – accurarcy of energy loss at high energy improved from 10% to 2% ●Mu pair production – updated parameterizations for E > 1 TeV – Precision of diff. cross section parameterization improved from 30% to 5% ●New processes: –   above 1 TeV) – e+e-     (high energy) ●Old EM processes kept in 52

7. 1 Compton Scattering Data, G4 LowE, G4 standard

8. 1 Stopping Power Data, G4 LowE, G4 Standard

9. 1 Photoelectric Effect Data, G4 LowE, G4 Standard

10. 1 Pair Production Data, G4 LowE, G4 Standard

11. 1 Multiple Scattering (1)

12. 1 Multiple Scattering (2) 0.0213 0. 0213 (. 0029 ) 0.58 g/cm 2 Pb 174 GeV 6.466.39(.18) 1.82 g/cm 2 Be 158. 6 MeV 23.8824.00(.24) 1.82 g/cm 2 Pb 158. 6 MeV 35.435.6(1.9) 3. 42 mg/cm 2 Al 1.984 MeV Geant4  0 (mr) Data  0 (mr) TargetProton energy

13. 1 BaBar EM Calorimeter (EM shower shapes) Bhabha scattering data Geant4

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15. 1 Hadronic Physics Lists ● Choosing the right combination of models is a complex task: –many models to choose from –must mix and match according to physics goals ● Hadronic physics lists developed to make the job easier –really just educated guesses –meant as starting point for user to develop tailored physics list ● 24 hadronic physics lists currently provided –19 physics lists categorized according to 14 use cases –url: http://cmsdoc.cern.ch/~hpw/GHAD/HomePage/ –all can be downloaded and installed as part of toolkit in directory parallel to source

16. 1 Hadronic Physics Lists: Linear Collider ● LHEP ● low energy parameterized + high energy parameterized models ● fast ● relatively easy to use ● not particularly good results below a few GeV ● LHEP_GN ● gamma- and electro-nuclear suite added ● QGSP_BERT ● quark gluon string + Bertini cascade ● better results ● medium speed

17. 1 Hadronic Physics Lists: Linear Collider ● QGSP_BIC ● quark gluon string + binary cascade models ● best results overall ● slowest ● GQSP_HP, LHEP_HP ● high-precision neutron model added ● good for LC neutron fluxes

18. 1 Hadronic Model Development ● Cascade models –extend Bertini cascade to include kaons –improve NN elastic and charge-exchange cross sections in Binary cascade –optimize Binary and Bertini cascades for use in calorimeter physics lists ● String models –reduce lower bound for QGS model to 6 GeV –include anti-proton induced reactions –attempt to improve shower shapes ● Chiral Invariant Phase Space model –improved nucleon structure functions –include neutrino-induced reactions

19. 1 Hadronic Process Validation and Plans Physics testing –thin target tests (comparing single Geant4 process with data) –full setup tests (full physics and full geometry) Statistical testing –Too early, many models still under development Regression –Some tests done currently, more are planned

20. 1 Gammas from 14 MeV Neutron Capture on U (Data driven model)

21. 1 Elastic Kaon Scattering at 800 MeV/c

22. 1  Production from 730 MeV p (LEP Model)

23. 1  Production from 730 MeV p (Bertini Model)

24. 1 Multiplicity in pp  X at 200 GeV/c (QGS Model)

25. 1 Cross section for p Li  + X at 400 GeV (QGS Model)

26. 1 Atlas HEC (e/  ratio)

27. 1 Validation at Experiments ATLAS –Test beam studies BaBar –Running experiment –Geant4 in production for two years GLAST –Cosmic ray balloon tests HARP –Running test beam experiment –Results to be used to validate Geant4 thin target studies

28. 1 HARP Experiment and Goals p and  beams between 1.5 and 15 GeV/c on solid targets (Be through Pb) and liquid targets (H 2, D 2,N 2, H 2 O) Provide a systematic study of hadron production cross sections Will provide much-needed data for Geant4 hadronic model validation and tuning Data taking complete, analysis underway

29. 1 Summary Electromagnetic physics – model approach migration continues (bugs fixed) – new models to be added – statistical and regression tests being performed – several processes are being extended Hadronic physics – hadronic physics lists available as a first step toward developing a detailed physics list – model development continues – validation of hadronic physics continues