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

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 02.04.2008

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 02.04.2008

Electron transport V.Ivanchenko 02.04.2008

Sampling Calorimeters V.Ivanchenko 02.04.2008

Muon transport Cut 1 mm V.Ivanchenko 02.04.2008

Fixed muon bremsstrahlung plot of E. Goudzovski NA49 9.1 9.0 V.Ivanchenko 02.04.2008

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 02.04.2008

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 02.04.2008

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 02.04.2008

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 02.04.2008

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 02.04.2008

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 02.04.2008

Infinite cuts V.Ivanchenko 02.04.2008

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 02.04.2008

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 02.04.2008

9.1ref03 tests results V.Ivanchenko 02.04.2008

9.1ref03 results for calorimeters CMS-type ATLAS-type V.Ivanchenko 02.04.2008

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 02.04.2008

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 02.04.2008