HOWTO run LAr G4 simulation with AtlasG4Sim using the geometry translated from GeoModel

To run LAr G4 simulation using the geometry translated from GeoModel, you should follow the standard way of running ATLAS simulation with AtlasG4Sim package described on the ATLAS Simulation web page. The only difference is that you need to edit the file AtlasGeoModel.mac, in particular replace the line

/macro/execute LArCal.mac

by

/macro/execute LArGeoGeometry.mac
/macro/execute LArGeoSensitive.mac

The first macro LArGeoGeometry.mac translates the GeoModel description of LAr calorimeter to Geant4 using Geo2G4 converter:

/Geometry/GetFacility GeoDetector LArBarrel:LArBarrel
/CALO/AddDetector LArBarrel
/Geometry/GetFacility GeoDetector LArEndcap:LArEndcap
/CALO/AddDetector LArEndcap

As you can see this macro builds the geometry of LAr barrel and endcap independently.

The second macro LArGeoSensitive.mac uses FADS-specific machinery to select sensitive detectors from the store and assign them to the logical volumes

/load LArG4HitManagement
/load LArG4Sim
/load LArG4SD

/LArControl/OutOfTimeCut 2.5 ns

/SenDetector/UseSensitiveDetector LAr::EMB::STAC LAr::EMB::STAC
/SenDetector/UseSensitiveDetector LAr::Barrel::Presampler::Module LAr::Barrel::Presampler::Module
/SenDetector/UseSensitiveDetector LAr::EMEC::InnerWheel LAr::EMEC::InnerWheel
/SenDetector/UseSensitiveDetector LAr::EMEC::OuterWheel LAr::EMEC::OuterWheel
/SenDetector/UseSensitiveDetector LAr::Endcap::Presampler::LiquidArgon LAr::Endcap::Presampler::LiquidArgon
/SenDetector/UseSensitiveDetector LAr::FCAL::Module1::Gap LAr::FCAL::Module1::Gap
/SenDetector/UseSensitiveDetector LAr::FCAL::Module2::Gap LAr::FCAL::Module2::Gap
/SenDetector/UseSensitiveDetector LAr::FCAL::Module3::Gap LAr::FCAL::Module3::Gap
/SenDetector/UseSensitiveDetector LAr::HEC::Module::Depth::Slice LAr::HEC::Module::Depth::Slice

/Geometry/AssignSD LArBarrel LArBarrel::LAr::EMB::STAC LAr::EMB::STAC
/Geometry/AssignSD LArBarrel LArBarrel::LAr::Barrel::PresamplerModule LAr::Barrel::Presampler::Module
/Geometry/AssignSD LArEndcap LArEndcap::LAr::EMEC::InnerWheel LAr::EMEC::InnerWheel
/Geometry/AssignSD LArEndcap LArEndcap::LAr::EMEC::OuterWheel LAr::EMEC::OuterWheel
/Geometry/AssignSD LArEndcap LArEndcap::LAr::Endcap::Presampler::LiquidArgon LAr::Endcap::Presampler::LiquidArgon
/Geometry/AssignSD LArEndcap LArEndcap::LAr::FCAL::Module1::Gap LAr::FCAL::Module1::Gap
/Geometry/AssignSD LArEndcap LArEndcap::LAr::FCAL::Module2::Gap LAr::FCAL::Module2::Gap
/Geometry/AssignSD LArEndcap LArEndcap::LAr::FCAL::Module3::Gap LAr::FCAL::Module3::Gap
/Geometry/AssignSD LArEndcap LArEndcap::LAr::HEC::Module::Depth::Slice LAr::HEC::Module::Depth::Slice

This macro also uses two libraries from LArG4. LArG4HitManagement - for hit persistency and LArG4Sim - for setting Out Of Time Cut value.

Thank you for trying that and giving us your feedback!