1. Status of Standard EM for Geant4 9.1 and Beyond
A.Bagulya, A.Bogdanov, S.Elles, V.Ivanchenko, O.Kadri, R.Kokoulin, M.Maire, L.Urban
on behalf of the Geant4 EM physics group
CERN, Geneva, Switzerland
2 April 2008

2. Outline Modifications with g4 9.1
Selected validation results for g4 9.1
Fixes in EM package for 9.1p01
New developments after 9.1
New helper class G4EmSaturation – Birks law
Corrections to hadron ionization
Hadron bremsstrahlung and e+e- pair production
Muon multiple scattering
EM Physics constructors
Conclusions
V.Ivanchenko

3. Main deliverables with g4 9.1
Fixed simulation of tail of μ-bremsstrahlung (NA49 request)
Improved simulation for ions:
G4ScreenedNuclearRecoil process released (Vanderbilt development)
NIEL energy filled
Improved Ion fluctuations
Fixed leaks at initialization for material and EM standard
Multiple/single scattering
Single scattering model updated – can be used for low-dense media
Multiple scattering was updated to achieve more stability versus cut/step limit change
G4MuMultipleScattering
V.Ivanchenko

4. Electron transport
V.Ivanchenko

5. Sampling Calorimeters
V.Ivanchenko

6. Muon transport
Cut 1 mm
V.Ivanchenko

7. Fixed muon bremsstrahlung
plot of E. Goudzovski NA49
9.1
9.0
V.Ivanchenko

8. Fixes provided for g4 9.1patch01
Fixed computation of NIEL
Proper initialization of NIEL variable
Correct simulation of the last step of a hadron
Fix ready for 9.1patch02:
Low-energy ions (about 200 eV) may looping in technical vacuum
V.Ivanchenko

9. New developments (g4 9.1ref03)
G4EmSaturation helper class
Hadron induced bremsstrahlung and e+e- pair production (LHCb and CMS requests)
Revised corrections to hadron ionization (LHCb request)
Updated EM Physics Lists
Multiple and single scattering
G4eMultipleScattering
V.Ivanchenko

10. Simulation of Birks effect
G4EmSaturation class is available
Can be used in user actions and G4Scintillation process
Special treatment of photo-electric effect, nuclear recoil and NIEL
Birks coefficient may be defined by user or taken from predefined list for NIST materials
V.Ivanchenko

11. Radiation processes for hadrons
New processes G4hBremsstrahlung and G4hPairProduction are available
Not yet included in reference Physics Lists
Can be applied for pions and protons
V.Ivanchenko

12. Finite size correction
Review of the finite size correction
Takes into account formfactor of a projectile hadron
Was added to continuous energy loss only
New version:
Small effect on peak dE/dx for default or small cuts
Suppressed large energy transfers
V.Ivanchenko

13. Response of vertex detectors
At high energies muons and pions may produce gamma and e+e- pairs in a field of atomic nucleus
High energy delta-rays, gamma and e+e- pairs are not effect the response of thin silicon
V.Ivanchenko

14. Infinite cuts
V.Ivanchenko

15. Muon deep penetration
Balance between CPU and correct results is needed
If step size is limited only by ionisation and msc the max cut 1 cm provides more than 1 step in an absorber
Additional step limitation by 10 cm allows to work with higher cuts
V.Ivanchenko

16. EM Physics Lists Physics Lists Builders Names in UI of examples QGSP
G4EmStandardPhysics
emstandard
QGSP_EMV
G4EmStandardPhysics_option1
emstandard_opt1
QGSP_EMX
G4EmStandardPhysics_option2
emstandard_opt2 -
G4EmStandardPhysics_option3
emstandard_opt3
standardSS, NR, IG
Default and opt1 for LHC – should be stable
Opt2 – advance options can be used for LHC
Opt3 for medical and other applications – maximum precision
V.Ivanchenko

17. 9.1ref03 tests results
V.Ivanchenko

18. 9.1ref03 results for calorimeters
CMS-type
ATLAS-type
V.Ivanchenko

19. Conclusions Number of new developments with g4 9.1ref03
Relevant to LHC experiment
Effects or improvements are small
Will be delivered with 9.2?
We put our efforts to keep results of main Physics List (QGSP, QGSP_EMV) stable
Extend testing suite
particle types
different energies
different use-cases
Physically split msc processes per particle type
perform separate upgrade per particle type
Development of alternative models
is in progress
V.Ivanchenko

20. Personal comment
What value of cuts can be appreciated by a G4 EM expert?
Below cut = 1 um our models not perfect
Above cut = 10 cm we would suggest to use GFLASH approach instead of using the Standard EM package with infinite cut
For deep penetration we would suggest to consider to use extra step limitation
V.Ivanchenko