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Rivet analyses reference

OPAL_1995_I393503

$K^0$ Production in Hadronic $Z^0$ Decays
Experiment: OPAL (LEP)
Inspire ID: 393503
Status: VALIDATED
Authors:
  • Peter Richardson
References:
  • Z.Phys. C67 (1995) 389-402, 1995
Beams: e+ e-
Beam energies: (45.6, 45.6) GeV
Run details:
  • Hadronic Z decay events generated on the Z pole ($\sqrt{s} = 91.2$ GeV)

The production of $K^0$ mesons measured using 1.3 millon $Z^0$ events by the OPAL experiment at LEP. Only the fragmentation function is implemented.

Source code: OPAL_1995_I393503.cc
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// -*- C++ -*-
#include "Rivet/Analysis.hh"
#include "Rivet/Projections/FinalState.hh"
#include "Rivet/Projections/ChargedFinalState.hh"
#include "Rivet/Projections/UnstableParticles.hh"
#include "Rivet/Projections/Beam.hh"

namespace Rivet {


  /// @brief  kaon spectra at LEP1
  class OPAL_1995_I393503 : public Analysis {
  public:

    /// Constructor
    DEFAULT_RIVET_ANALYSIS_CTOR(OPAL_1995_I393503);


    /// @name Analysis methods
    //@{

    /// Book histograms and initialise projections before the run
    void init() {
      declare(Beam(), "Beams");
      declare(ChargedFinalState(), "FS");
      declare(UnstableParticles(), "UFS");

      // Book histograms
      book(_h_K0_x , 2, 1, 1);
      book(_h_K0_xi, 3, 1, 1);

    }


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

      // First, veto on leptonic events by requiring at least 4 charged FS particles
      const FinalState& fs = apply<FinalState>(event, "FS");
      const size_t numParticles = fs.particles().size();

      // Even if we only generate hadronic events, we still need a cut on numCharged >= 2.
      if (numParticles < 2) {
        MSG_DEBUG("Failed leptonic event cut");
        vetoEvent;
      }
      MSG_DEBUG("Passed leptonic event cut");

      // Get beams and average beam momentum
      const ParticlePair& beams = apply<Beam>(event, "Beams").beams();
      const double meanBeamMom = ( beams.first.p3().mod() +
                                   beams.second.p3().mod() ) / 2.0;
      MSG_DEBUG("Avg beam momentum = " << meanBeamMom);

      // Final state of unstable particles to get particle spectra
      const UnstableParticles& ufs = apply<UnstableFinalState>(event, "UFS");

      for (const Particle& p : ufs.particles(Cuts::pid==130 or
					     Cuts::pid==310)) {
        double xp = p.p3().mod()/meanBeamMom;
	_h_K0_x->fill(xp);
	_h_K0_xi->fill(-log(xp));
      }

    }


    /// Normalise histograms etc., after the run
    void finalize() {
      scale(_h_K0_x, 1./sumOfWeights());
      scale(_h_K0_xi, 1./sumOfWeights());
    }

    //@}


    /// @name Histograms
    //@{
    Histo1DPtr _h_K0_x,_h_K0_xi;
    //@}


  };


  // The hook for the plugin system
  DECLARE_RIVET_PLUGIN(OPAL_1995_I393503);


}