Rivet analyses

title: BESIII_2019_I1712729

$J/\psi\to \phi\eta\eta^\prime$

Experiment: BESIII (BEPC)

Inspire ID: 1712729

Status: VALIDATED NOHEPDATA

Authors: - Peter Richardson

References: - Phys.Rev.D 99 (2019) 11, 112008

Beams: * *

Beam energies: ANY

Run details: - Any process producing J/psi originally e+e-

Measurement of the mass distributions in the decay $J/\psi\to \phi\eta\eta^\prime$. The data were read from the plots in the paper. It is also not clear that any resolution effects have been unfolded.

Source code:BESIII_2019_I1712729.cc

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

include "Rivet/Analysis.hh"

include "Rivet/Projections/DecayedParticles.hh"

include "Rivet/Projections/UnstableParticles.hh"

namespace Rivet {

/// @brief J/psi -> phi eta eta' class BESIII_2019_I1712729 : public Analysis { public:

/// Constructor
RIVET_DEFAULT_ANALYSIS_CTOR(BESIII_2019_I1712729);


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

/// Book histograms and initialise projections before the run
void init() {
  UnstableParticles ufs = UnstableParticles(Cuts::pid == 443);
  declare(ufs, "UFS");
  DecayedParticles psi(ufs);
  psi.addStable(PID::PI0);
  psi.addStable(PID::K0S);
  psi.addStable(PID::ETA);
  psi.addStable(PID::ETAPRIME);
  psi.addStable(PID::OMEGA);
  psi.addStable(PID::PHI);
  declare(psi, "psi");
  for (unsigned int ix = 0; ix < 2; ++ix) book(_h[ix], 1, 1, 1 + ix);
  book(_dalitz, "dalitz", 50, 3.5, 7., 50, 2.0, 5.);
}


/// Perform the per-event analysis
void analyze(const Event& event) {
  static const map<PdgId, unsigned int>& mode = {{333, 1}, {221, 1}, {331, 1}};
  DecayedParticles psi = apply<DecayedParticles>(event, "psi");
  // loop over particles
  for (unsigned int ix = 0; ix < psi.decaying().size(); ++ix) {
    if (!psi.modeMatches(ix, 3, mode)) continue;
    const Particle& phi = psi.decayProducts()[ix].at(333)[0];
    const Particle& eta = psi.decayProducts()[ix].at(221)[0];
    const Particle& etap = psi.decayProducts()[ix].at(331)[0];
    double mphieta = (phi.momentum() + eta.momentum()).mass2();
    double mphietap = (phi.momentum() + etap.momentum()).mass2();
    _h[0]->fill(sqrt(mphietap));
    _h[1]->fill(sqrt(mphietap));
    _dalitz->fill(mphietap, mphieta);
  }
}


/// Normalise histograms etc., after the run
void finalize() {
  for (unsigned int ix = 0; ix < 2; ++ix) normalize(_h[ix]);
  normalize(_dalitz);
}

/// @}


/// @name Histograms
/// @{
Histo1DPtr _h[2];
Histo2DPtr _dalitz;
/// @}

};

RIVET_DECLARE_PLUGIN(BESIII_2019_I1712729);

} ```