1. Status of CHIPS cross sections and migration of the physics lists
Witek Pokorski

2. Goal
remove all the dependencies on CHIPS from the Geant4 production physics lists
extract (clone) the CHIPS cross sections used by other physics lists (models)
change the inheritance to use the standard Geant4 base classes
implement the standard methods, etc
remove any use of CHIPS classes (PDG, etc)
put them all in hadronic/cross_sections according to the Geant4 toolkit design allowing proper dependency of modules

3. Inelastic cross sections
inelastic cross sections for K+/-/0, Pi+/-, p, n, hyperons, anti-baryons have been extracted from CHIPS and put in hardonic/cross_sections
naming convention: G4ChipsKaonMinusInelasticXS.hh
inheriting from G4VCrossSectionDataSet
no any dependency on CHIPS, no singleton, follows standard G4 interface for cross sections
can be used directly in physics list and handled by G4CrossSectionDataStore
removed use of ‘tolerance’ (see later)

4. Elastic cross sections
elastic cross sections for K+/-/0, Pi+/-, p, n, hyperons, anti-baryons have been extracted from CHIPS and put in hardonic/cross_sections
naming convention: G4ChipsKaonMinusElasticXS.hh
inheriting from G4VCrossSectionDataSet
no any dependency on CHIPS, no singleton, follows standard G4 interface for cross sections
can be used directly in physics list and handled by G4CrossSectionDataStore
no use of ‘tolerance’

5. Issues in CHIPS cross-sections (1/2)
all CHIPS (inelastic) cross sections use ‘tolerance’
if |new_momentum - old_momentum| < tolerance*p, use the same cross section, do not recompute
physically acceptable approximation, but totally breaks reproducibility
confirmed to be one of the remaining sources of the problems observed by Alberto
fixed by Vladimir I., but commented out
for instance FTFP_BERT still using the K cross-sections with tolerance
removed use of tolerance in the new (extracted) cross section classes

6. Issues in CHIPS cross-sections (2/2)
for K0 the following code is used in the current CHIPS interface
else if(particle == G4KaonZeroLong::KaonZeroLong() ||
particle == G4KaonZeroShort::KaonZeroShort() ||
particle == G4KaonZero::KaonZero() ||
particle == G4AntiKaonZero::AntiKaonZero() ) {
CSmanager=G4QKaonZeroNuclearCrossSection::GetPointer();
if(G4UniformRand() > 0.5) pPDG= 311;
else pPDG=-311; }
uses random number to randomly choose between K0 and anti-K0

7. Issues in CHIPS cross-sections (2/2)- continued
but... pPDG (the randomly chosen), not used anywhere afterwards....
instead GetCrossSection for K0 returns
G4double CS=(theKMinusCS->GetCrossSection(fCS,pMom,tgZ,tgN,-321)
+theKPlusCS->GetCrossSection(fCS,pMom,tgZ,tgN,321))/2;
the new class follows (for the moment?) this approach

8. Component cross sections class
common (optional) ‘interface’ to elastic and inelastic has been implemented
G4ChipsComponentXS in hadronic/cross_sections
allows to access all the cross sections (for all particles) through one class
gives also the total cross section

9. Migrations of models (1/2)
in parton_string/diffraction there was a direct use of CHIPS cross sections
this has been migrated to the new cross sections
see G4FTFParameters
the old interface G4ComponentCHIPShadronNuclearXS from parton_string/diffraction can now be removed

10. Migration of models (2/2)
in coherent_elastic there was the interface G4CHIPSElasticXS to CHIPS elastic cross sections and to the CHIPS elastic process (G4CHIPSElastic)
new interface has been implemented G4ChipsElasticModel for the elastic process
new cross sections can be used now directly (because they inherit from G4VCrossSectionDataSet)

11. Migration of physics lists
G4HadronElasticPhysics and G4HadronDElasticPhysics migrated to new elastic scattering classes (cross sections)
G4HyperonFTFPBuilder, HadronPhysicsFTFP_BERT and HadronPhysicsFTFP_BERT_TRV migrated to new cross sections
FTFP_BERT and FTFP_BERT_TRV physics lists now use the new cross sections classes
Andrea has run the simplified calorimeter with the new cross sections
no crashes, no problems
results show no differences

12. Conclusion ‘Cloning’ of CHIPS cross sections done
reproducibility problems solved in the same time
processes using those cross sections internally (coherent elastic, FTF) has been migrated to the new ones
in SVN, tagged, accepted
FTFP_BERT physics list migrated to the new cross sections
first validation results show no problems
ready to put in the next reference tag and in the beta release