refactor: Split particle selection in Examples (#3969)

- split particle selection into three stages: after generation, after simulation, after digitization
- this allows to perform cuts on the particle collections independent from the algorithms processing them
- after digitization cuts allow to cut on measurement count
- elevates particle selection into reconstruction chain

blocked by
- #4035

<!-- This is an auto-generated comment: release notes by coderabbit.ai -->

## Summary by CodeRabbit

# Release Notes: Particle Processing and Naming Convention Update

## Overview
This release introduces significant improvements to particle processing workflows, focusing on more precise particle selection and standardized naming conventions.

## Key Changes

### Particle Selection
- Added new functions for particle selection at different stages:
  - `addGenParticleSelection`: Selects particles during generation
  - `addSimParticleSelection`: Selects particles during simulation
  - `addDigiParticleSelection`: Selects particles during digitization

### Naming Conventions
- Updated particle-related variable names from `particles_input` to `particles_generated`
- Standardized input/output particle identifiers across multiple scripts and workflows

### Particle Filtering
- Simplified particle selection logic
- Removed inline particle selection configurations
- Enhanced modularity in particle processing

## Impact
- Improved clarity in particle handling
- More flexible and consistent particle selection
- Better separation of concerns in simulation workflows

<!-- end of auto-generated comment: release notes by coderabbit.ai -->

CI/physmon/workflows/physmon_simulation.py

@@ -8,7 +8,6 @@
 from acts.examples.simulation import (
     addFatras,
     addGeant4,
-    ParticleSelectorConfig,
     addPythia8,
 )
 
@@ -58,7 +57,7 @@
                     acts.PdgParticle.eElectron,
                 ]
             ],
-            outputParticles="particles_input",
+            outputParticles="particles_generated",
             outputVertices="vertices_input",
             randomNumbers=rnd,
         )
@@ -67,7 +66,7 @@
     s.addWriter(
         acts.examples.RootParticleWriter(
             level=acts.logging.INFO,
-            inputParticles="particles_input",
+            inputParticles="particles_generated",
             filePath=tp / "particles.root",
         )
     )
@@ -78,9 +77,7 @@
         setup.field,
         rnd,
         enableInteractions=True,
-        preSelectParticles=None,
-        postSelectParticles=ParticleSelectorConfig(removeSecondaries=True),
-        inputParticles="particles_input",
+        inputParticles="particles_generated",
         outputParticles="particles_fatras",
         outputSimHits="simhits_fatras",
         outputDirRoot=tp / "fatras",
@@ -92,12 +89,10 @@
         setup.trackingGeometry,
         setup.field,
         rnd,
-        preSelectParticles=None,
-        postSelectParticles=ParticleSelectorConfig(removeSecondaries=True),
         killVolume=setup.trackingGeometry.highestTrackingVolume,
         killAfterTime=25 * u.ns,
         killSecondaries=True,
-        inputParticles="particles_input",
+        inputParticles="particles_generated",
         outputParticles="particles_geant4",
         outputSimHits="simhits_geant4",
         outputDirRoot=tp / "geant4",

CI/physmon/workflows/physmon_trackfinding_1muon.py

@@ -11,9 +11,10 @@
     EtaConfig,
     PhiConfig,
     ParticleConfig,
-    ParticleSelectorConfig,
     addFatras,
     addDigitization,
+    ParticleSelectorConfig,
+    addDigiParticleSelection,
 )
 
 from acts.examples.reconstruction import (
@@ -72,11 +73,6 @@ def run_ckf_tracking(label, seeding):
             setup.field,
             enableInteractions=True,
             rnd=rnd,
-            postSelectParticles=ParticleSelectorConfig(
-                pt=(0.9 * u.GeV, None),
-                hits=(9, None),
-                removeNeutral=True,
-            ),
         )
 
         addDigitization(
@@ -87,6 +83,15 @@ def run_ckf_tracking(label, seeding):
             rnd=rnd,
         )
 
+        addDigiParticleSelection(
+            s,
+            ParticleSelectorConfig(
+                pt=(0.9 * u.GeV, None),
+                measurements=(9, None),
+                removeNeutral=True,
+            ),
+        )
+
         addSeeding(
             s,
             setup.trackingGeometry,

CI/physmon/workflows/physmon_trackfinding_4muon_50vertices.py

@@ -11,9 +11,10 @@
     EtaConfig,
     PhiConfig,
     ParticleConfig,
-    ParticleSelectorConfig,
     addFatras,
     addDigitization,
+    ParticleSelectorConfig,
+    addDigiParticleSelection,
 )
 from acts.examples.reconstruction import (
     addSeeding,
@@ -69,11 +70,6 @@
         setup.trackingGeometry,
         setup.field,
         rnd=rnd,
-        postSelectParticles=ParticleSelectorConfig(
-            pt=(0.9 * u.GeV, None),
-            hits=(9, None),
-            removeNeutral=True,
-        ),
     )
 
     addDigitization(
@@ -84,6 +80,15 @@
         rnd=rnd,
     )
 
+    addDigiParticleSelection(
+        s,
+        ParticleSelectorConfig(
+            pt=(0.9 * u.GeV, None),
+            measurements=(9, None),
+            removeNeutral=True,
+        ),
+    )
+
     addSeeding(
         s,
         setup.trackingGeometry,

CI/physmon/workflows/physmon_trackfinding_ttbar_pu200.py

@@ -7,9 +7,11 @@
 import acts
 from acts.examples.simulation import (
     addPythia8,
+    ParticleSelectorConfig,
+    addGenParticleSelection,
     addFatras,
     addDigitization,
-    ParticleSelectorConfig,
+    addDigiParticleSelection,
 )
 from acts.examples.reconstruction import (
     addSeeding,
@@ -61,20 +63,19 @@
         outputDirRoot=tp,
     )
 
+    addGenParticleSelection(
+        s,
+        ParticleSelectorConfig(
+            rho=(0.0, 24 * u.mm),
+            absZ=(0.0, 1.0 * u.m),
+        ),
+    )
+
     addFatras(
         s,
         setup.trackingGeometry,
         setup.field,
         rnd=rnd,
-        preSelectParticles=ParticleSelectorConfig(
-            rho=(0.0, 24 * u.mm),
-            absZ=(0.0, 1.0 * u.m),
-        ),
-        postSelectParticles=ParticleSelectorConfig(
-            pt=(0.5 * u.GeV, None),
-            hits=(9, None),
-            removeNeutral=True,
-        ),
     )
 
     addDigitization(
@@ -85,6 +86,15 @@
         rnd=rnd,
     )
 
+    addDigiParticleSelection(
+        s,
+        ParticleSelectorConfig(
+            pt=(0.5 * u.GeV, None),
+            measurements=(9, None),
+            removeNeutral=True,
+        ),
+    )
+
     addSeeding(
         s,
         setup.trackingGeometry,

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

@@ -2149,9 +2149,9 @@ def addVertexFitting(
         trackParameters = converter.config.outputTrackParameters
 
     tracks = tracks if tracks is not None else ""
-    inputParticles = "particles_input"
+    inputParticles = "particles"
     selectedParticles = "particles_selected"
-    inputTruthVertices = "vertices_input"
+    inputTruthVertices = "vertices_truth"
 
     if vertexFinder == VertexFinder.Truth:
         findVertices = TruthVertexFinder(
@@ -2245,7 +2245,7 @@ def addSingleSeedVertexFinding(
     )
     s.addAlgorithm(findSingleSeedVertex)
 
-    inputParticles = "particles_input"
+    inputParticles = "particles"
     selectedParticles = "particles_selected"
 
     if outputDirRoot is not None: