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DELPHI_1995_I394052

$K^\pm$ and $p,\bar{p}$ spectra in hadronic $Z^0$ decays
Experiment: DELPHI (LEP)
Inspire ID: 394052
Status: VALIDATED
Authors:
  • Peter Richardson
References:
  • Nucl.Phys. B444 (1995) 3-26, 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)

DELPHI results for the spectra for $K^\pm$ and $p,\bar{p}$ production in hadronic $Z^0$ decays.

Source code: DELPHI_1995_I394052.cc
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// -*- C++ -*-
#include "Rivet/Analysis.hh"
#include "Rivet/Projections/FinalState.hh"
#include "Rivet/Projections/ChargedFinalState.hh"
#include "Rivet/Projections/Beam.hh"

namespace Rivet {


  /// @brief K+/- and protno spectra
  class DELPHI_1995_I394052 : public Analysis {
  public:

    /// Constructor
    DEFAULT_RIVET_ANALYSIS_CTOR(DELPHI_1995_I394052);


    /// @name Analysis methods
    //@{

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

      // Book histograms
      book(_h_kaon_p   , 3, 1, 1);
      book(_h_kaon_x   , 5, 1, 1);
      book(_h_proton_p , 4, 1, 1);
      book(_h_proton_x , 6, 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);
      for (const Particle& p : fs.particles(Cuts::abspid==321 or
					       Cuts::abspid==2212)) {
	double modp = p.p3().mod();
        double xp = modp/meanBeamMom;
	if(abs(p.pid())==321) {
	  _h_kaon_p  ->fill(modp);
	  _h_kaon_x  ->fill(xp  );
	}
	else {
	  _h_proton_p->fill(modp);
	  _h_proton_x->fill(xp  );
	}
      }
    }


    /// Normalise histograms etc., after the run
    void finalize() {
      scale(_h_kaon_p  ,1./sumOfWeights());
      scale(_h_kaon_x  ,1./sumOfWeights());
      scale(_h_proton_p,1./sumOfWeights());
      scale(_h_proton_x,1./sumOfWeights());
    }

    //@}


    /// @name Histograms
    //@{
    Histo1DPtr _h_kaon_p, _h_kaon_x, _h_proton_p, _h_proton_x;
    //@}


  };


  // The hook for the plugin system
  DECLARE_RIVET_PLUGIN(DELPHI_1995_I394052);


}