examples: standalone dRICH GDML example (Geant4 + Simphony side-by-side) - #347
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examples: standalone dRICH GDML example (Geant4 + Simphony side-by-side)#347ggalgoczi wants to merge 4 commits into
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examples/drich runs the single-sector dRICH from a geoConverter-exported GDML through Geant4 (CPU) and Opticks (GPU), no DD4hep, comparing optical-photon hits. Driver + 0.2mm-airgap GDML + build/run README. Depends on the CSG phi-wedge and qbnd POINT/sibling-pair changes.
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May 29, 2026 14:10
Gives examples/drich the standalone CMakeLists.txt (find_package eic-opticks + Geant4 gdml) and run.sh that the sibling examples carry, so the no-DD4hep dRICH driver builds the canonical way. Compiling it serves as a build-smoke for the standalone GDML flow; README gains the CMake recipe.
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Adds tests/test_drich_gdml.sh (run on the [gpu] CI runner alongside the other test_*.sh) that runs the standalone dRICH example through Geant4 CPU and Opticks GPU side-by-side and asserts the sensor-hit counts agree within NSIGMA*sqrt(G+C) (Poisson). Builds the example via its CMakeLists if no binary is installed. SKIPs (benign) without a GPU or if the rare G4 navigator hang times out every seed. Wired into build-pull-request.yaml's GPU test step.
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The geoConverter-exported dRICH fixture from PR #347 defines optical sensor skin surfaces but does not identify their logical volumes as Geant4 sensitive detectors. simg4ox constructs PhotonSD instances from the GDML auxiliary map, so photons reaching these surfaces are otherwise absent from the Geant4 hit collection and cannot be compared with Opticks GPU hits. Add a SensDet=PhotonDetector auxiliary record to each of the 210 DRICH_pss logical volumes. This preserves the original solids, placements, materials, and optical surfaces while allowing the CPU simulation to attach PhotonSD instances and record the sensor hits needed by the dRICH integration comparison.
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The dRICH GDML exported by DD4hep stores optical-property energy axes in GeV, while Geant4 imports the raw matrix coordinates using its MeV-based internal units. This leaves material and surface spectra 1000 times below their intended energies, moving them outside the optical-photon range and suppressing physical transport and detection. Scale the energy coordinate of all 41 two-column property tables by 1000 while preserving their property values. Also model the photon-sensor surface as unified dielectric-metal with explicit zero reflectivity so Geant4 enters the EFFICIENCY absorption/detection path rather than applying dielectric Fresnel transport or reflecting photons before detection. These corrections encode the import-time adjustments from the PR #347 standalone dRICH driver directly in the reusable fixture, enabling consistent Geant4 CPU and Opticks GPU hit comparisons while retaining all 210 sensitive-detector annotations.
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examples/drich runs the single-sector dRICH from a geoConverter-exported GDML through Geant4 (CPU) and Opticks (GPU), no DD4hep, comparing optical-photon hits. Driver + 0.2mm-airgap GDML + build/run README. Depends on the CSG phi-wedge and qbnd POINT/sibling-pair changes.