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CDF_2009_S8436959

Measurement of the inclusive isolated prompt photon cross-section
Experiment: CDF (Tevatron Run 2)
Inspire ID: 834437
Status: VALIDATED
Authors:
  • Frank Siegert
References: Beams: p- p+
Beam energies: (980.0, 980.0) GeV
Run details:
  • $\gamma$ + jet processes in ppbar collisions at $\sqrt{s} = 1960$ GeV. Minimum pT cut on the photon in the analysis is 30 GeV.

A measurement of the cross section for the inclusive production of isolated photons. The measurement covers the pseudorapidity region $|\eta^\gamma|<1.0$ and the transverse energy range $E_T^\gamma>30$ GeV and is based on 2.5 fb$^{-1}$ of integrated luminosity. The cross section is measured differential in $E_\perp(\gamma)$.

Source code: CDF_2009_S8436959.cc
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// -*- C++ -*-
#include "Rivet/Analysis.hh"
#include "Rivet/Projections/FinalState.hh"
#include "Rivet/Projections/LeadingParticlesFinalState.hh"

namespace Rivet {


  /// @brief CDF inclusive isolated prompt photon cross-section
  class CDF_2009_S8436959 : public Analysis {
  public:

    /// @name Constructors etc.
    //@{

    /// Constructor
    CDF_2009_S8436959()
      : Analysis("CDF_2009_S8436959")
    {    }

    //@}


  public:

    /// @name Analysis methods
    //@{

    /// Book histograms and initialise projections before the run
    void init() {
      FinalState fs;
      declare(fs, "FS");

      LeadingParticlesFinalState photonfs(FinalState(-1.0, 1.0, 30.0*GeV));
      photonfs.addParticleId(PID::PHOTON);
      declare(photonfs, "LeadingPhoton");

      _h_Et_photon = bookHisto1D(1, 1, 1);
    }


    /// Perform the per-event analysis
    void analyze(const Event& event) {
      const double weight = event.weight();

      Particles fs = apply<FinalState>(event, "FS").particles();
      Particles photons = apply<LeadingParticlesFinalState>(event, "LeadingPhoton").particles();
      if (photons.size()!=1) {
        vetoEvent;
      }
      FourMomentum leadingPhoton = photons[0].momentum();
      double eta_P = leadingPhoton.eta();
      double phi_P = leadingPhoton.phi();
      FourMomentum mom_in_cone;
      foreach (const Particle& p, fs) {
        if (deltaR(eta_P, phi_P, p.eta(), p.phi()) < 0.4) {
            mom_in_cone += p.momentum();
        }
      }
      if ( (mom_in_cone.Et() - leadingPhoton.Et()) > 2.0*GeV) {
        vetoEvent;
      }
      _h_Et_photon->fill(leadingPhoton.Et(), weight);
    }


    /// Normalise histograms etc., after the run
    void finalize() {
      scale(_h_Et_photon, crossSection()/sumOfWeights()/2.0);
    }

    //@}


  private:

    /// @name Histograms
    //@{
    Histo1DPtr _h_Et_photon;
    //@}

  };



  // The hook for the plugin system
  DECLARE_RIVET_PLUGIN(CDF_2009_S8436959);

}