FTAG: add another truth label for light jet studies & improve alg config

This MR makes three changes:

• updating the ftagTruthTypeLabel to include a category for lambdas
• adding a new ftagTruthSourceLabel (someone please let me know if you have a better name), which gives info about the immediate parent of the TP (rather than the ftagTruthOriginLabel which gives origin info further up the chain in general). This is added to facilitate studies of mis-tagging in light jets.
• adds configurable accessors which is needed for re-running the labelling downstream (see atlas-flavor-tagging-tools/training-dataset-dumper!556 (merged))

cc @fdibello

PhysicsAnalysis/JetTagging/FlavorTagDiscriminants/FlavorTagDiscriminants/SoftElectronTruthDecoratorAlg.h

@@ -35,21 +35,43 @@ namespace FlavorTagDiscriminants {
       this, "electronContainer", "Electrons",
         "Key for the input electron collection"};
 
+    // Accessors for truth particles
+    using RDHK = SG::ReadDecorHandleKey< xAOD::TruthParticleContainer >;
+    RDHK m_acc_origin_label {
+      this, "acc_ftagTruthOriginLabel", "ftagTruthOriginLabel", 
+        "Accessor for the truth origin label of the truth particle"};
+    RDHK m_acc_type_label {
+      this, "acc_ftagTruthTypeLabel", "ftagTruthTypeLabel", 
+        "Accessor for the truth type label of the truth particle"};
+    RDHK m_acc_source_label {
+      this, "acc_ftagTruthSourceLabel", "ftagTruthSourceLabel", 
+        "Accessor for the truth source label of the truth particle"};
+    RDHK m_acc_vertex_index {
+      this, "acc_ftagTruthVertexIndex", "ftagTruthVertexIndex", 
+        "Accessor for the truth vertex index of the truth particle"};
+    RDHK m_acc_parent_barcode {
+      this, "acc_ftagTruthParentBarcode", "ftagTruthParentBarcode", 
+        "Accessor for the truth parent barcode of the truth particle"};
+
     // Decorators for electrons
-    SG::WriteDecorHandleKey< xAOD::ElectronContainer > m_dec_origin_label {
-      this, "ftagTruthOriginLabel", "ftagTruthOriginLabel", 
+    using WDHK = SG::WriteDecorHandleKey< xAOD::ElectronContainer >;
+    WDHK m_dec_origin_label {
+      this, "dec_ftagTruthOriginLabel", "ftagTruthOriginLabel", 
         "Exclusive origin label of the electron"};
-    SG::WriteDecorHandleKey< xAOD::ElectronContainer > m_dec_type_label {
-      this, "ftagTruthTypeLabel", "ftagTruthTypeLabel", 
+    WDHK m_dec_type_label {
+      this, "dec_ftagTruthTypeLabel", "ftagTruthTypeLabel", 
         "Exclusive truth type label of the electron"};
-    SG::WriteDecorHandleKey< xAOD::ElectronContainer > m_dec_vertex_index {
-      this, "ftagTruthVertexIndex", "ftagTruthVertexIndex", 
+    WDHK m_dec_source_label {
+      this, "dec_ftagTruthSourceLabel", "ftagTruthSourceLabel", 
+        "Exclusive truth label for the immedate parent of the truth particle"};
+    WDHK m_dec_vertex_index {
+      this, "dec_ftagTruthVertexIndex", "ftagTruthVertexIndex", 
         "Truth vertex index of the electron"};
-    SG::WriteDecorHandleKey< xAOD::ElectronContainer > m_dec_barcode {
-      this, "ftagTruthBarcode", "ftagTruthBarcode", 
+    WDHK m_dec_barcode {
+      this, "dec_ftagTruthBarcode", "ftagTruthBarcode", 
         "Barcode of linked truth particle"};
-    SG::WriteDecorHandleKey< xAOD::ElectronContainer > m_dec_parent_barcode {
-      this, "ftagTruthParentBarcode", "ftagTruthParentBarcode", 
+    WDHK m_dec_parent_barcode {
+      this, "dec_ftagTruthParentBarcode", "ftagTruthParentBarcode", 
         "Barcode of parent of linked truth particle"};
 
     // truth origin tool
@@ -65,10 +87,6 @@ namespace FlavorTagDiscriminants {
     template <typename T> using Acc = SG::AuxElement::ConstAccessor<T>;
     Acc<unsigned int> m_classifierParticleType{"classifierParticleType"};
     Acc<ElementLink<xAOD::TruthParticleContainer>> m_truthParticleLink{"truthParticleLink"};
-    Acc<int> m_acc_truthOriginLabel{"ftagTruthOriginLabel"};
-    Acc<int> m_acc_truthTypeLabel{"ftagTruthTypeLabel"};
-    Acc<int> m_acc_truthVertexIndex{"ftagTruthVertexIndex"};
-    Acc<int> m_acc_truthParentBarcode{"ftagTruthParentBarcode"};
   };
 }