Transition from Associations to Links

```
Calorimetery/CaloDebugTools/CheckClustParEP/CheckClustParEPProcessor.h
52: make_pair("HcalEndcapNClusters", "HcalEndcapNClusterAssociations"),
53: make_pair("EcalEndcapNClusters", "EcalEndcapNClusterAssociations"),
54: make_pair("HcalBarrelClusters", "HcalBarrelClusterAssociations"),
55: make_pair("EcalBarrelClusters", "EcalBarrelClusterAssociations"),
56: make_pair("LFHCALClusters", "LFHCALClusterAssociations"),
57: make_pair("EcalEndcapPClusters", "EcalEndcapPClusterAssociations")

Calorimetery/MergeBHCalTiles/ClusterMergedHits/ClusterMergedHitsProcessor.cc
80: "HcalBarrelRawHitAssociations"},
82: "HcalBarrelMergedHitClusterAssociationsWithoutShapes"},
98: "HcalBarrelMergedHitClusterAssociationsWithoutShapes"},
100: "HcalBarrelMergedHitClusterAssociations"},

Calorimetery/ReadAssociationsAndContributions/README.md
1:# Read Associations of and Contributions to a Reconstructed Cluster

ElectronID/ElectronID.cc
91: const auto& RecoMC = static_cast(*(mEvent->get("ReconstructedParticleAssociations")));
106: const auto& RecoMC = static_cast(*(mEvent->get("ReconstructedParticleAssociations")));
362: const auto& RecoMC = static_cast(*(mEvent->get("ReconstructedParticleAssociations")));

Calorimetery/CaloDebugTools/HCalDebugTreeMaker/RelationalHCalDebugTreeMakerProcessor.h
72: "HcalEndcapNClusterAssociations",

Calorimetery/ReadAssociationsAndContributions/ReadInAssociationsAndContributions.cxx
2:// 'ReadInAssociationsAndContributions.cxx'
11:// root -b -q ReadInAssociationsAndContributions.cxx++
53: "LFHCALClusterAssociations",
61:void ReadInAssociationsAndContributions(const Options& opt = DefaultOptions) {

JetsAndHF/HF/D0_helix/analysis.cxx
159: TTreeReaderArray assocChSimID = {treereader, "ReconstructedChargedParticleAssociations.simID"};
160: TTreeReaderArray assocChRecID = {treereader, "ReconstructedChargedParticleAssociations.recID"};
161: TTreeReaderArray assocWeight = {treereader, "ReconstructedChargedParticleAssociations.weight"};

JetsAndHF/JetValidation/JetValidation.C
180: TTreeReaderArray recoPartAssocRec = {tree_reader, "_ReconstructedChargedParticleAssociations_rec.index"}; // Reco <-> MCParticle
181: TTreeReaderArray recoPartAssocSim = {tree_reader, "_ReconstructedChargedParticleAssociations_sim.index"};
182: TTreeReaderArray recoPartAssocWeight = {tree_reader, "ReconstructedChargedParticleAssociations.weight"};
361: for(unsigned int n=0; n assocChSimID = {treereader, "_ReconstructedChargedParticleAssociations_sim.index"};
358:TTreeReaderArray assocChRecID = {treereader, "_ReconstructedChargedParticleAssociations_rec.index"};
359:TTreeReaderArray assocWeight = {treereader, "ReconstructedChargedParticleAssociations.weight"};
539: map assoc_map_mc_to_rc; // MC --> RC Associations
540: map assoc_map_rc_to_mc; // RC --> MC Associations

JetsAndHF/SecondaryVertex_Chi2/analysis.cxx
353: TTreeReaderArray assocChSimID = {treereader, "_ReconstructedChargedParticleAssociations_sim.index"};
354: TTreeReaderArray assocChRecID = {treereader, "_ReconstructedChargedParticleAssociations_rec.index"};
355: TTreeReaderArray assocWeight = {treereader, "ReconstructedChargedParticleAssociations.weight"};

JetsAndHF/eFinder/find_ScatElectron.C
71: TTreeReaderArray rc_index = {treereader, "_ReconstructedParticleAssociations_rec.index"};
72: TTreeReaderArray mc_index = {treereader, "_ReconstructedParticleAssociations_sim.index"};

JetsAndHF/jetReaderExamples/jetReader_TTreeReader.C
43: //TTreeReaderArray recoPartAssocRec = {tree_reader, "ReconstructedChargedParticleAssociations.recID"}; // Reco <-> MCParticle
44: //TTreeReaderArray recoPartAssocSim = {tree_reader, "ReconstructedChargedParticleAssociations.simID"};
47: TTreeReaderArray recoPartAssocRec = {tree_reader, "_ReconstructedChargedParticleAssociations_rec.index"}; // Reco <-> MCParticle
48: TTreeReaderArray recoPartAssocSim = {tree_reader, "_ReconstructedChargedParticleAssociations_sim.index"};
50: TTreeReaderArray recoPartAssocWeight = {tree_reader, "ReconstructedChargedParticleAssociations.weight"};
226: for(unsigned int n=0; n in_hit_assocs = {this, "DIRCRawHitsAssociations"};

Tracking/DISAnalysis/DIS_reconstruction.C
158: TTreeReaderArray assoc_rec_id(tr, "ReconstructedChargedParticleAssociations.recID");
159: TTreeReaderArray assoc_sim_id(tr, "ReconstructedChargedParticleAssociations.simID");
160: TTreeReaderArray assoc_weight(tr, "ReconstructedChargedParticleAssociations.weight");
162: TTreeReaderArray assoc_ts_rec_id(tr, "ReconstructedTruthSeededChargedParticleAssociations.recID");
163: TTreeReaderArray assoc_ts_sim_id(tr, "ReconstructedTruthSeededChargedParticleAssociations.simID");
164: TTreeReaderArray assoc_ts_weight(tr, "ReconstructedTruthSeededChargedParticleAssociations.weight");

Tracking/DISAnalysis/hit_based_matching.C
140: TTreeReaderArray hit_assoc_weight_ts(tr,"CentralCKFTruthSeededTrackAssociations.weight");
141: TTreeReaderArray hit_assoc_mc_ts(tr, "_CentralCKFTruthSeededTrackAssociations_sim.index");
142: TTreeReaderArray hit_assoc_track_ts(tr, "_CentralCKFTruthSeededTrackAssociations_rec.index");
144: TTreeReaderArray hit_assoc_weight_rs(tr,"CentralCKFTrackAssociations.weight");
145: TTreeReaderArray hit_assoc_mc_rs(tr, "_CentralCKFTrackAssociations_sim.index");
146: TTreeReaderArray hit_assoc_track_rs(tr, "_CentralCKFTrackAssociations_rec.index");

Tracking/PerformanceStudy/SinglePion/pTDR/io.py
69: assoc_name="CentralCKFTrackAssociations",

Tracking/PerformanceStudy/SinglePion/pTDR/run_study.py
229: assoc_name="CentralCKFTrackAssociations",
339: parser.add_argument("--assoc-name", default="CentralCKFTrackAssociations")

Tracking/PerformanceStudy/SinglePion/plot_single_resol.py
74:assoc_name = 'CentralCKFTrackAssociations'

Tracking/TrackHitContributions/hit_matching.C
454: auto& raw_hit_assocs = f.get("CentralTrackingRawHitAssociations");

Tracking/TrackMetrics/TrackMetrics.C
174: "CentralTrackingRawHitAssociations"

Tree_Pruning/TreePrune.C
59: full_tree->SetBranchStatus("ReconstructedChargedParticleAssociations*",1);

Tracking/BackgroundStudy/epic_analysis_ak_example.ipynb
1092: " asso=event.get(\"CentralTrackingRawHitAssociations\") \n",
1173: " asso=event.get(\"CentralTrackingRawHitAssociations\")\n",
1505: "asso = event.get(\"CentralTrackingRawHitAssociations\")\n",
```
cc https://github.com/eic/EICrecon/pull/2822

Start with the association-to-link changes in EICrecon PR 2822, then inspect the listed C++, Python, and notebook files for references to the affected collection names. Update the affected analysis examples and macros consistently, and verify that no listed association references remain where the new link representation is required.

Written by the indexing model from the issue text.