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JADE_1990_I282847

Photon, $\pi^0$ and $\eta$ spectra in $e^+e^-$ collisions at 35 and 44 GeV
Experiment: JADE (Petra)
Inspire ID: 282847
Status: VALIDATED
Authors:
  • Peter Richardson
References:
  • Z.Phys. C46 (1990) 1-7, 1990
Beams: e+ e-
Beam energies: (17.5, 17.5); (22.0, 22.0) GeV
Run details:
  • e+ e- to hadrons

Measurement of the Photon, $\pi^0$ and $\eta$ spectra in $e^+e^-$ collisions at 35 and 44 GeV by the JADE experiment at Petra. The isolated photon spectrum which tests ISR and FST QED radiation is not implemented. The multiplicities are not implemented as they are in the PDG averages.

Source code: JADE_1990_I282847.cc
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// -*- C++ -*-
#include "Rivet/Analysis.hh"
#include "Rivet/Projections/FinalState.hh"
#include "Rivet/Projections/UnstableParticles.hh"
#include "Rivet/Projections/Beam.hh"

namespace Rivet {


  /// @brief gamma, pi0 and eta spectra at 35 and 44 GeV
  class JADE_1990_I282847 : public Analysis {
  public:

    /// Constructor
    DEFAULT_RIVET_ANALYSIS_CTOR(JADE_1990_I282847);


    /// @name Analysis methods
    //@{

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

      int ioff=-1;
      if(fuzzyEquals(sqrtS()/GeV,35.,1e-3)) {
      	ioff=0;
      }
      else if(fuzzyEquals(sqrtS()/GeV,44.,1e-3)) {
      	ioff=1;
      }
      else
      	MSG_ERROR("Beam energy " << sqrtS() << " not supported!");
      // Book histograms
      book(_h_gamma, 1+ioff, 1, 1);
      book(_h_pi0  , 3+ioff, 1, 1);
      if(ioff==0) book(_h_eta, 5+ioff, 1, 1);
    }


    /// Perform the per-event analysis
    void analyze(const Event& event) {
      // 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;
      // gamma
      const FinalState& fs = apply<FinalState>(event, "FS");
      for (const Particle& p : fs.particles(Cuts::pid==22)) {
      	double xE = p.E()/meanBeamMom;
      	_h_gamma->fill(xE);
      }
      // pi0, eta
      const UnstableParticles& ufs = apply<UnstableParticles>(event, "UFS");
      for (const Particle& p : ufs.particles(Cuts::pid==111 or Cuts::pid==221)) {
      	double modp = p.p3().mod();
      	double xE = p.E()/meanBeamMom;
      	double beta = modp/p.E();
      	if(p.pid()==111)
      	  _h_pi0->fill(xE,1./beta);
      	else if(_h_eta)
      	  _h_eta->fill(xE,1./beta);
      }
    }


    /// Normalise histograms etc., after the run
    void finalize() {
      scale(_h_gamma, crossSection()*sqr(sqrtS())/microbarn/sumOfWeights());
      scale(_h_pi0  , crossSection()*sqr(sqrtS())/microbarn/sumOfWeights());
      if(_h_eta) scale(_h_eta  , crossSection()*sqr(sqrtS())/microbarn/sumOfWeights());
    }

    //@}

    /// @name Histograms
    //@{
    Histo1DPtr _h_gamma, _h_pi0, _h_eta;
    //@}

  };


  // The hook for the plugin system
  DECLARE_RIVET_PLUGIN(JADE_1990_I282847);


}