Rivet analyses

title: MC_PDFS

Analysis to study PDF sampling in any MC run

Experiment: ()

Status: VALIDATED

Authors: - Andy Buckley

References: none listed

Beams: * *

Beam energies: ANY

Run details: - Any!

Plotting of PDF sampling info, such as the $Q^2$ and both $x$ values of the sampling (aggregated and distinguished as max/min, and some correlations with event properties.

Source code:MC_PDFS.cc

```c++ // -- C++ --

include "Rivet/Analysis.hh"

// #include "Rivet/Projections/ChargedFinalState.hh"

namespace Rivet {

/// Generic analysis looking at various distributions of final state particles class MC_PDFS : public Analysis { public:

/// Constructor
MC_PDFS()
    : Analysis("MC_PDFS") { }

public:

/// @name Analysis methods
/// @{

/// Book histograms and initialise projections before the run
void init() {
  // Projections
  // declare(ChargedFinalState((Cuts::etaIn(-5.0, 5.0) && Cuts::pT >=  500*MeV)), "CFS");

  // Histograms
  book(_histPdfX, "PdfX", logspace(50, 0.000001, 1.0));
  book(_histPdfXmin, "PdfXmin", logspace(50, 0.000001, 1.0));
  book(_histPdfXmax, "PdfXmax", logspace(50, 0.000001, 1.0));
  book(_histPdfQ, "PdfQ", 50, 0.0, 30.0);
  book(_histPdfXQ, "PdfXQ", logspace(50, 0.000001, 1.0), linspace(50, 0.0, 30.0));
  //book( _histPdfTrackptVsX ,"PdfTrackptVsX", logspace(50, 0.000001, 1.0));
  //book( _histPdfTrackptVsQ ,"PdfTrackptVsQ", 50, 0.0, 30.0);
}


/// Perform the per-event analysis
void analyze(const Event& event) {

  // This analysis needs a valid HepMC PDF info object to do anything
  if (event.genEvent()->pdf_info() == 0) vetoEvent;
  PdfInfo pdfi = *(event.genEvent()->pdf_info());

  MSG_DEBUG("PDF Q = " << pdfi.scale << " for (id, x) = "
                       << "(" << pdfi.parton_id[0] << ", " << pdfi.x[0] << ") "
                       << "(" << pdfi.parton_id[1] << ", " << pdfi.x[1] << ")");
  _histPdfX->fill(pdfi.x[0]);
  _histPdfX->fill(pdfi.x[1]);
  _histPdfXmin->fill(std::min(pdfi.x[0], pdfi.x[1]));
  _histPdfXmax->fill(std::max(pdfi.x[0], pdfi.x[1]));
  _histPdfQ->fill(pdfi.scale);             // always in GeV?
  _histPdfXQ->fill(pdfi.x[0], pdfi.scale); // always in GeV?
  _histPdfXQ->fill(pdfi.x[1], pdfi.scale); // always in GeV?

  // const FinalState& cfs = apply<FinalState>(event, "CFS");
  // for (const Particle& p : cfs.particles()) {
  //   if (fabs(eta) < 2.5 && p.pT() > 10*GeV) {
  //     _histPdfTrackptVsX->fill(pdfi.x1(), p.pT()/GeV);
  //     _histPdfTrackptVsX->fill(pdfi.x2(), p.pT()/GeV);
  //     _histPdfTrackptVsQ->fill(pdfi.scalePDF(), p.pT()/GeV);
  //   }
  // }
}


/// Finalize
void finalize() {
  scale(_histPdfX, 1 / sumOfWeights());
  scale(_histPdfXmin, 1 / sumOfWeights());
  scale(_histPdfXmax, 1 / sumOfWeights());
  scale(_histPdfQ, 1 / sumOfWeights());
}

/// @}

private:

/// @name Histograms
/// @{
Histo1DPtr _histPdfX, _histPdfXmin, _histPdfXmax, _histPdfQ;
Histo2DPtr _histPdfXQ;
// Profile1DPtr   _histPdfTrackptVsX, _histPdfTrackptVsQ;
/// @}

};

RIVET_DECLARE_PLUGIN(MC_PDFS);

} ```