RAD | User Guide

The Recipe-Based Architecture

RAD utilizes an AnalysisManager that compartmentalizes your code into Recipes (C++ Lambdas). This ensures execution safety, multi-threading stability, and keeps your analysis logic incredibly clean.

Initialization: Define the data source and map your particle candidates.
Combinatorics: The engine automatically maps all valid multiparticle topologies.
Topology Recipe: A sandboxed function where you build the decay chains and define variables.
Histogram Recipe: A dedicated scope for booking 1D and 2D plots.

1Setup & Candidates

Initialize the Analysis Manager, set your beam parameters, and assign your track roles before generating combinations.

// 1. Enable Parallel Processing
ROOT::EnableImplicitMT(8);

// 2. Initialize the Manager
AnalysisManager<HepMCElectro, KinematicsProcElectro> mgr{
  "Jpsi_Analysis", // Analysis Name
  "hepmc3_tree",   // Tree Name
  "data.root"      // Input File
};
mgr.SetOutputDir("output");

auto& reaction = mgr.Reaction();
reaction.SetupMC();

// 3. Map Particle Roles
reaction.SetBeamElectronIndex(0);
reaction.SetBeamIonIndex(1);
reaction.SetScatElectronIndex(2); 

reaction.SetParticleIndex("p", 3);
reaction.SetParticleIndex("ele", 4); 
reaction.SetParticleIndex("pos", 5); 

// 4. Expand into unique combinations & add data stream
reaction.MakeCombinations();
mgr.AddStream(rad::MC());
    

2The Topology Recipe

Define how intermediate particles are constructed (Sums/Diffs) and what physics variables to calculate for every combination.

// 5. The Topology Lambda (Injected to all CPU threads)
auto topology_recipe = [](KinematicsProcElectro& p) {
  
  // A. Reconstruct J/psi -> e+ e- (Vector Sum)
  p.Creator().Sum("Jpsi", {{"ele", "pos"}});         
  
  // Or reconstruct missing tracks (Vector Diff)
  // p.Creator().Diff("miss", {{rad::consts::BeamEle(), rad::consts::BeamIon()}, {rad::consts::ScatEle(), "Jpsi", "p"}});

  // B. Assign Groups
  p.SetMesonParticles({"Jpsi"});
  p.SetBaryonParticles({"p"});
  
  // C. Calculate Invariant Masses
  p.Mass("MassJ", {"Jpsi"});             
  
  // D. Standard Calculations & Angles
  p.RegisterCalc("tb", rad::physics::TBot);
  p.ParticleTheta({{"scat_ele", "Jpsi", "p"}});
  p.ParticleP({{"scat_ele", "Jpsi", "p"}});
};
    

3Histograms & Execution

Define your plots targeting the variables created above, configure the manager, and run the lazy evaluation.

// 6. The Histogram Recipe
auto histogram_recipe = [](rad::histo::Histogrammer& h) {
  // Args: Name, Title/Axes, Bins, Min, Max, Target Column
  h.Create("MassJ", "Invariant Mass J/psi; Mass [GeV]", 100, 2.0, 4.0, "MassJ");
  h.Create2D("hPvsTheta", "P vs Theta", 100, 0.0, 10.0, 100, 0.0, 3.14, "p_pmag", "p_theta");
};

// 7. Inject Recipes into the Manager
mgr.ConfigureKinematics(topology_recipe);
mgr.ConfigureHistograms(histogram_recipe);

// 8. Trigger Lazy Evaluation (The Event Loop)
mgr.Snapshot(); // Prepares the flat TTree
mgr.Run();      // Executes RDataFrame!
    