Rivet analyses

title: L3_1997_I427107

$\eta^\prime$ and $\omega$ spectra at 91 GeV

Experiment: L3 (LEP)

Inspire ID: 427107

Status: VALIDATED

Authors: - Peter Richardson

References: - Phys.Lett. B393 (1997) 465-476, 1997

Beams: e- e+

Beam energies: (45.6, 45.6)GeV

Run details: - e+ e- to hadrons at the Z pole

Measurement of the momentum distribution of the $\eta^\prime$ and $\omega$ mesons at 91.2 GeV in $e^+e^-$ collisions.

Source code:L3_1997_I427107.cc

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

include "Rivet/Analysis.hh"

include "Rivet/Projections/Beam.hh"

include "Rivet/Projections/ChargedFinalState.hh"

include "Rivet/Projections/UnstableParticles.hh"

namespace Rivet {

/// @brief eta' and omega production at mz class L3_1997_I427107 : public Analysis { public:

/// Constructor
RIVET_DEFAULT_ANALYSIS_CTOR(L3_1997_I427107);


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

/// Book histograms and initialise projections before the run
void init() {

  // Initialise and register projections
  declare(Beam(), "Beams");
  declare(ChargedFinalState(), "FS");
  declare(UnstableParticles(), "UFS");

  // // Book histograms
  book(_histXpOmega, 5, 1, 1);
  book(_histLnXpOmega, 6, 1, 1);
  book(_histXpEtaP1, 7, 1, 1);
  book(_histLnXpEtaP1, 8, 1, 1);
  book(_histXpEtaP2, 9, 1, 1);
  book(_histLnXpEtaP2, 10, 1, 1);
}


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

  // Even if we only generate hadronic events, we still need a cut on numCharged >= 2.
  const FinalState& fs = apply<FinalState>(event, "FS");
  if (fs.particles().size() < 2) {
    MSG_DEBUG("Failed ncharged cut");
    vetoEvent;
  }
  MSG_DEBUG("Passed ncharged 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 Particles& mesons = apply<UnstableParticles>(event, "UFS")
                                .particles(Cuts::pid == PID::ETAPRIME or Cuts::pid == PID::OMEGA);

  for (const Particle& p : mesons) {
    double xp = p.p3().mod() / meanBeamMom;
    double xi = log(1. / xp);
    if (p.pid() == PID::ETAPRIME) {
      _histXpEtaP1->fill(xp);
      _histLnXpEtaP1->fill(xi);
      _histXpEtaP2->fill(xp);
      _histLnXpEtaP2->fill(xi);
    }
    else {
      _histXpOmega->fill(xp);
      _histLnXpOmega->fill(xi);
    }
  }
}


/// Normalise histograms etc., after the run
void finalize() {
  scale(_histXpEtaP1, 1. / sumOfWeights());
  scale(_histLnXpEtaP1, 1. / sumOfWeights());
  scale(_histXpEtaP2, 1. / sumOfWeights());
  scale(_histLnXpEtaP2, 1. / sumOfWeights());
  scale(_histXpOmega, 1. / sumOfWeights());
  scale(_histLnXpOmega, 1. / sumOfWeights());
}

/// @}


/// @name Histograms
/// @{
Histo1DPtr _histXpEtaP1, _histXpEtaP2;
Histo1DPtr _histLnXpEtaP1, _histLnXpEtaP2;
Histo1DPtr _histXpOmega;
Histo1DPtr _histLnXpOmega;
/// @}

};

RIVET_DECLARE_PLUGIN(L3_1997_I427107);

} ```