TPC: add UseGeant4Edep ionisation-fluctuation flag for Kr-83m calibration simulations#15615
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TPC: add UseGeant4Edep ionisation-fluctuation flag for Kr-83m calibration simulations#15615Ankyyadav wants to merge 5 commits into
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July 16, 2026 12:33
…-83m calibration Adds a boolean flag TPCDetParam.UseGeant4Edep (default false) that switches ProcessHits' ionisation calculation from the standard Bethe-Bloch/NA49 collision-sampling model to the direct Geant4 energy deposit (fMC->Edep()), with Fano-limited Gamma-distributed smearing via ScaleFactorG4/FanoFactorG4 (TPCGasParam), matching the O2 Geant4-specific ionisation model used before commit 7860b87. A SetSpecialPhysicsCuts() override sets 1 keV VMC cuts on the TPC drift gas mediums before simcuts.dat is read, ensuring Auger electrons (1.921 keV minimum) are tracked and not killed early. The flag is off by default so the normal simulation chain is unaffected. Activate for Kr calibration via: --configKeyValues "TPCDetParam.UseGeant4Edep=1"
…ration-generator # Conflicts: # Detectors/TPC/simulation/src/Detector.cxx
Ankyyadav
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July 21, 2026 09:25
Please consider the following formatting changes to AliceO2Group#15615
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TPCDetParam.UseGeant4Edep, an opt-in flag (default off) that uses Geant4's energy deposit directly for ionisation inDetector::ProcessHits, with Fano-limited charge fluctuation via a Gamma-distributed smear (mean/variance tuned for GEANT4). Used for 83mKr TPC calibration simulations.SetSpecialPhysicsCuts()callsmatmgr.SpecialCut()for the TPC drift-gas media before the base class readssimcuts.dat(which sets a 10 keV default for these media). This is now exposed asTPCDetParam.SpecialCutsGeV(default 1e-6 GeV = 1 keV), so the actual effective cutcan be set via configKeyValues.