refactor: Enable Fatras interactions by default / make configurable i…

…n addFatras(...) (#1631)

It turned out that all interactions in Fatras where turned off by default... This is not optimal I think. This PR enables these by default both on the C++ site and on the python side, to be explicit.

As a consequence, all root hashes relying on FATRAs should change...

Examples/Algorithms/Fatras/include/ActsExamples/Fatras/FatrasSimulation.hpp

@@ -49,15 +49,15 @@ class FatrasSimulation final : public BareAlgorithm {
     /// Minimal absolute momentum for particles to be simulated.
     double pMin = 0.5 * Acts::UnitConstants::GeV;
     /// Simulate (multiple) scattering for charged particles.
-    bool emScattering = false;
+    bool emScattering = true;
     /// Simulate ionisiation/excitation energy loss of charged particles.
-    bool emEnergyLossIonisation = false;
+    bool emEnergyLossIonisation = true;
     /// Simulate radiative energy loss of charged particles.
-    bool emEnergyLossRadiation = false;
+    bool emEnergyLossRadiation = true;
     /// Simulate electron-positron pair production by photon conversion.
-    bool emPhotonConversion = false;
+    bool emPhotonConversion = true;
     /// Generate simulation hits on sensitive surfaces.
-    bool generateHitsOnSensitive = false;
+    bool generateHitsOnSensitive = true;
     /// Generate simulation hits on surfaces with associated material.
     bool generateHitsOnMaterial = false;
     /// Generate simulation hits on passive surfaces, i.e neither sensitive nor

Examples/Python/python/acts/examples/simulation.py

@@ -363,6 +363,7 @@ def addFatras(
     outputDirRoot: Optional[Union[Path, str]] = None,
     rnd: Optional[acts.examples.RandomNumbers] = None,
     preselectParticles: Optional[ParticleSelectorConfig] = ParticleSelectorConfig(),
+    enableInteractions=False,
     logLevel: Optional[acts.logging.Level] = None,
 ) -> None:
     """This function steers the detector simulation using Fatras
@@ -383,6 +384,7 @@ def addFatras(
         ParticleSelector configuration to select particles as input to Fatras. Each range is specified as a tuple of (min,max).
         Default of no selections specified in Examples/Algorithms/TruthTracking/ActsExamples/TruthTracking/ParticleSelector.hpp
         Specify preselectParticles=None to inhibit ParticleSelector altogether.
+    enableInteractions : Enable the particle interactions in the simulation
     """
 
     customLogLevel = acts.examples.defaultLogging(s, logLevel)
@@ -413,6 +415,10 @@ def addFatras(
         trackingGeometry=trackingGeometry,
         magneticField=field,
         generateHitsOnSensitive=True,
+        emScattering=enableInteractions,
+        emEnergyLossIonisation=enableInteractions,
+        emEnergyLossRadiation=enableInteractions,
+        emPhotonConversion=enableInteractions,
     )
 
     # Sequencer

Examples/Python/tests/conftest.py

@@ -332,6 +332,10 @@ def _factory(s):
             trackingGeometry=trk_geo,
             magneticField=field,
             generateHitsOnSensitive=True,
+            emScattering=False,
+            emEnergyLossIonisation=False,
+            emEnergyLossRadiation=False,
+            emPhotonConversion=False,
         )
 
         s.addAlgorithm(simAlg)