Rivet analyses

title: MC_PHOTONINC

Monte Carlo validation observables for single isolated photon production

Experiment: ()

Status: VALIDATED

Authors: - Frank Siegert

References: none listed

Beams: * *

Beam energies: ANY

Run details: - Tevatron Run II ppbar -> gamma + jets.

Monte Carlo validation observables for single isolated photon production

Source code:MC_PHOTONINC.cc

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

include "Rivet/Analysis.hh"

include "Rivet/Projections/LeadingParticlesFinalState.hh"

include "Rivet/Projections/VetoedFinalState.hh"

namespace Rivet {

/// @brief MC validation analysis for single photon events class MC_PHOTONINC : public Analysis { public:

/// Default constructor
MC_PHOTONINC()
    : Analysis("MC_PHOTONINC") { }


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

/// Book histograms
void init() {
  // General FS
  FinalState fs((Cuts::etaIn(-5.0, 5.0)));
  declare(fs, "FS");

  // set photon cuts from input options
  const double etacut = getOption<double>("ABSETAGAMMAX", 2.5);
  const double ptcut = getOption<double>("PTGAMMIN", 30.);

  // Get leading photon
  LeadingParticlesFinalState photonfs(FinalState(Cuts::abseta < etacut && Cuts::pT >= ptcut * GeV));
  photonfs.addParticleId(PID::PHOTON);
  declare(photonfs, "LeadingPhoton");

  // FS for isolation excludes the leading photon
  VetoedFinalState vfs(fs);
  vfs.addVetoOnThisFinalState(photonfs);
  declare(vfs, "JetFS");

  book(_h_photon_pT, "photon_pT", logspace(50, 30.0, 0.5 * (sqrtS() > 0. ? sqrtS() : 14000.)));
  book(_h_photon_pT_lin, "photon_pT_lin", 50, 0.0, 70.0);
  book(_h_photon_y, "photon_y", 50, -5.0, 5.0);
}


/// Do the analysis
void analyze(const Event& e) {
  // Get the photon
  const Particles photons = apply<FinalState>(e, "LeadingPhoton").particles();
  if (photons.size() != 1) {
    vetoEvent;
  }
  const FourMomentum photon = photons.front().momentum();

  // Get all charged particles
  const FinalState& fs = apply<FinalState>(e, "JetFS");
  if (fs.empty()) {
    vetoEvent;
  }

  // Passed cuts, so get the weight

  // Isolate photon by ensuring that a 0.4 cone around it contains less than 7% of the photon's energy
  const double egamma = photon.E();
  double econe = 0.0;
  for (const Particle& p : fs.particles()) {
    if (deltaR(photon, p.momentum()) < 0.4) {
      econe += p.E();
      // Veto as soon as E_cone gets larger
      if (econe / egamma > 0.07) {
        vetoEvent;
      }
    }
  }

  _h_photon_pT->fill(photon.pT());
  _h_photon_pT_lin->fill(photon.pT());
  _h_photon_y->fill(photon.rapidity());
}


// Finalize
void finalize() {
  scale(_h_photon_pT, crossSectionPerEvent());
  scale(_h_photon_pT_lin, crossSectionPerEvent());
  scale(_h_photon_y, crossSectionPerEvent());
}

/// @}

private:

/// @name Histograms
/// @{
Histo1DPtr _h_photon_pT;
Histo1DPtr _h_photon_pT_lin;
Histo1DPtr _h_photon_y;
/// @}

};

RIVET_DECLARE_PLUGIN(MC_PHOTONINC);

} ```