added new gPhotonDetector routine, similar to flux but only records optical photons. it does not require recordZeroEdep to be set. cherenkov detector modified to use it

Author: maureeungaro

README.md

@@ -21,7 +21,7 @@ The project goal is to make Geant4-based simulation accessible to users who want
 - Geometry and material storage in SQLite or GEMC ASCII databases
 - Geometry imports from native GEMC databases, GDML, and CAD meshes
 - Run-number and variation support for reusable detector configurations
-- Built-in sensitive detector digitizations: `flux`, `dosimeter`, and `particle_counter`
+- Built-in sensitive detector digitizations: `flux`, `gPhotonDetector`, `dosimeter`, and `particle_counter`
 - Dynamic C++ plugin infrastructure for custom digitization, fields, particle readers, and output streamers
 - Event generation from command-line/YAML particle definitions and Lund files
 - Output streamers for ASCII, CSV, JSON, JLAB SRO, and optional ROOT output

ci/install_examples_db.py

@@ -17,7 +17,7 @@
         "b3": {"runs": ["1", "11"], "variations": ["default", "alt"]},
     },
     "optical": {
-        "cherenkov": {"runs": ["1"], "variations": ["default", "CO2", "C4F10"]},
+        "cherenkov": {"runs": ["1"], "variations": ["default", "mediumIndexRadiator", "highIndexRadiator"]},
     },
 }
 

examples/meson.build

@@ -14,7 +14,7 @@ examples_map = {
         'b3' : { 'runs' : ['1', '11'], 'variations' : ['default', 'alt'] }
     },
     'optical' : {
-        'cherenkov' : { 'runs' : ['1'], 'variations' : ['default', 'CO2', 'C4F10'] },
+        'cherenkov' : { 'runs' : ['1'], 'variations' : ['default', 'mediumIndexRadiator', 'highIndexRadiator'] },
     }
 }
 

examples/optical/cherenkov/cherenkov.py

@@ -112,6 +112,6 @@
         backplate.material = material
 
         backplate.color = "lightgray"
-        backplate.digitization = "flux"
+        backplate.digitization = "gPhotonDetector"
         backplate.set_identifier("detector", panel_id)
         backplate.publish(cfg)

examples/optical/cherenkov/cherenkov.yaml

@@ -26,6 +26,3 @@ gparticle:
   - name: e-
     p: 1000
     vz: -50
-
-# Required for optical-photon flux hits because optical photons deposit zero energy.
-recordZeroEdep: true

gdetector/gdetectorConstruction.cc

@@ -8,6 +8,7 @@
 #include "gsystemConventions.h"
 #include "gDosimeterDigitization.h"
 #include "gFluxDigitization.h"
+#include "gPhotonDetectorDigitization.h"
 #include "gParticleCounterDigitization.h"
 
 // geant4
@@ -262,6 +263,9 @@ void GDetectorConstruction::loadDigitizationPlugins() {
 		if (sdname == FLUXNAME) {
 			log->info(1, "Loading flux digitization plugin for routine <" + sdname + ">");
 			digitization_routines_map->emplace(sdname, std::make_shared<GFluxDigitization>(gopt));
+		} else if (sdname == GPHOTON_DETECTORNAME) {
+			log->info(1, "Loading gPhotonDetector digitization plugin for routine <" + sdname + ">");
+			digitization_routines_map->emplace(sdname, std::make_shared<GPhotonDetectorDigitization>(gopt));
 		} else if (sdname == COUNTERNAME) {
 			log->info(1, "Loading particle counter digitization plugin for routine <" + sdname + ">");
 			digitization_routines_map->emplace(sdname, std::make_shared<GParticleCounterDigitization>(gopt));

gdynamicDigitization/gPhotonDetectorDigitization.cc

@@ -0,0 +1,22 @@
+#include "gPhotonDetectorDigitization.h"
+
+// geant4
+#include "G4OpticalPhoton.hh"
+#include "G4Step.hh"
+
+bool GPhotonDetectorDigitization::decisionToSkipHit(double energy, const G4Step* thisStep) {
+	if (thisStep == nullptr || thisStep->GetTrack() == nullptr) {
+		return true;
+	}
+
+	const auto* particle = thisStep->GetTrack()->GetDefinition();
+	if (particle != G4OpticalPhoton::OpticalPhotonDefinition()) {
+		return true;
+	}
+
+	if (energy == 0) {
+		return false;
+	}
+
+	return GDynamicDigitization::decisionToSkipHit(energy);
+}

gdynamicDigitization/gPhotonDetectorDigitization.h

@@ -0,0 +1,27 @@
+#pragma once
+
+#include "gFluxDigitization.h"
+
+/**
+ * \class GPhotonDetectorDigitization
+ * \brief Built-in digitization routine for optical-photon flux detectors.
+ *
+ * This routine records the same output fields as \c flux, but accepts only Geant4
+ * optical-photon steps. Optical photons are recorded even when they deposit zero
+ * energy, independent of the global \c recordZeroEdep switch.
+ */
+class GPhotonDetectorDigitization : public GFluxDigitization
+{
+public:
+	/// Inherit the base constructor (const std::shared_ptr<GOptions>&).
+	using GFluxDigitization::GFluxDigitization;
+
+	/**
+	 * \brief Keeps only optical-photon steps.
+	 *
+	 * \param energy Total deposited energy for the step.
+	 * \param thisStep Geant4 step being processed.
+	 * \return true when the step should be skipped.
+	 */
+	bool decisionToSkipHit(double energy, const G4Step* thisStep) override;
+};

gdynamicDigitization/gdynamicdigitization.h

@@ -472,6 +472,20 @@ class GDynamicDigitization : public GBase<GDynamicDigitization> {
         return false;
     }
 
+    /**
+     * \brief Decides whether a step should be skipped before hit creation.
+     *
+     * This overload gives digitization routines access to the full Geant4 step while
+     * preserving the legacy energy-only hook for existing plugins.
+     *
+     * \param energy Total deposited energy for the step.
+     * \param thisStep Geant4 step being processed.
+     * \return true if the step should be skipped.
+     */
+    virtual bool decisionToSkipHit(double energy, [[maybe_unused]] const G4Step* thisStep) {
+        return decisionToSkipHit(energy);
+    }
+
     /**
      * \brief Sets the options pointer required by the digitization base.
      *

gdynamicDigitization/meson.build

@@ -15,13 +15,15 @@ LD += {
     'sources' : files(
         'gdynamicdigitization.cc',
         'gFluxDigitization.cc',
+        'gPhotonDetectorDigitization.cc',
         'gParticleCounterDigitization.cc',
         'gDosimeterDigitization.cc',
         'gdynamicdigitization_options.cc'
     ),
     'headers' : files(
         'gdynamicdigitization_options.h',
         'gFluxDigitization.h',
+        'gPhotonDetectorDigitization.h',
         'gParticleCounterDigitization.h',
         'gDosimeterDigitization.h',
         'greadoutSpecs.h'