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EM Standard Physics Upgrade for Geant4 9.2

V.N.Ivanchenko, 3 December 2008

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J.Apostolakis, A.Bagulya, A.Bogdanov, S.Elles, V.Grichine, P.Gumplinger, O.Kadri, R.Kokoulin, M.Maire, A.Schaeliske, T.Toshito, L.Urban

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Outline List of new developments Highlights on upgrade of standard EM

physics Bremsstrahlung Multiple Scattering Spline option ApplyCuts option

Some validation results Conclusions

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New physics will available with g4 9.2 Relativistic bremsstrahlung model for E > 1 GeV

Updated density effect Hadron induced bremsstrahlung and e+e- pair production

processes/models Updated positron annihilation to hadrons G4eMultipleScattering process with G4UrbanMscModel2 G4MuMultipleScacttering process with G4WentzelVIModel G4Cerenkov process updated G4Scintillation process includes Birks low ICRU’73 data are inserted Ion ionisation updated

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New options and infrastructure components will be available with g4 9.2 Spline option for physics tables Option3 Standard Physics builder

Optimized for medical and space applications New utility classes:

G4EmSaturation – Birks effect (used in G4Scintillation) NIEL and gamma interactions

G4ElectronIonPair – helper class to sample of ionisation clusters at charge particle step using ICRU’31 approach

G4EmProcessSubType – enumerator of EM processes G4EmConfigurator – helper class to configure EM models per

energy range and G4Region

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Highlights on new developments which is available with 9.2

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Bremsstrahlung

Added new relativistic model bremsstrahlung model for e± Updated density and LPM

effects Applied above 1 GeV

Added new model for hadron bremsstrahlung and e+e- pair production In predefined PhysLists for

π± and protons

287 GeV e- at Ta target (4%X0)

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New relativistic bremsstrahlung modelA.Schaeliscke, IEEE NSS, 2008 Bethe-Heitler formula

with corrections Complete screening

with Coulomb correction Valid for E > 1 GeV

Density & LPM-Effect consistent combination

a’la Ter-Mikaelian

LPM old

LPM new

LPM off

Data from the CERN experiment: H.D.Hansen et al, PR D 69, 032001 (2004)

287 GeV e- at Ta target (4%X0)

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Updated multiple scattering

New specialized process for e± G4eMultipleScattering Uses G4UrbanMscModel2 tuned for electron data FR = 0.04

Old model G4UrbanMscModel is frozen Validation versus data and alternative models:

G4WentzelVIModel G4CoulombScattering

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Test of e- transport versus Sandia data(details in O.Kadri et al, NIM B258 (2007) 358) Sensitive to

multiple scattering Directly connected

with LHC calorimeters results

Tuned Urban’s msc model#2 is best in describing

data Label e-Msc, skin=3

Ta Al

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Upgrade of multiple scattering model

Old default version will be kept for backward compatibility

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Spline option for Physics Tables Spline interpolation

of dEdx, range and other tables

Zoomed Bragg peak Default EM physics

without spline (Opt0) strong cut

dependence Non-statistical

variations due to numerical instability

Spline is activated (Opt3) Stable result

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“ApplyCuts” option

“ApplyCuts” was inside the package for a long time By default is “false”

Production thresholds (cuts) are applied only for ionisation and bremsstrahlung

If “true” production thresholds are applied for all EM standard processes

Provides more fast simulation but may bias results if cuts are high (above 1 mm)

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ATLAS barrel type calorimeter EMV and EMX in this

plot use “ApplyCuts” Default Physics List

results unchanged Cut on gamma

processes (EMX) reduces accuracy of energy response but has no effect on EMV

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ATLAS HEC type calorimeter

Visible energy increased by 0.5%

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CMS ECAL type calorimeter

5x5 matrix of PW04

crystals Reduced (~0.5%)

energy deposition in central crystal both for the default and EMV Physics Lists Result of upgrade of

Urban multiple scattering model

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CPU benchmarking Static build on dedicated SLC4 PC

no libraries from afs

EM1 EM2 EM3 EM1_EMV EM2_EMV EM3_EMV

8.3 1.33 2.30 1.84 1.0 1.0 1.0

9.0 1.21 2.05 1.65 0.92 0.93 0.94

9.1p02 1.16 2.05 1.64 0.92 0.94 0.93

9.2 (ApplyCuts for EMV) 1.11 1.84 1.49 0.72 0.81 0.87

CPU gain with 9.0 mainly due to c++ software cleanup CPU gain with 9.2 due to optimization of physics

step limitation by multiple scattering energy threshold for gamma processes

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Summary

There are number of modifications in EM standard in g4 9.2, it is expected: better CPU performance and better agreement with test-

beam No change in total response and resolution for ECal Minor increase of response in sampling calorimeters with

low sampling fraction Apply Cuts option may significantly improve CPU

performance BUT Should be applied with care Cuts should be reviewed