Rivet analyses

Radiative J/ψ → γη^′η^′

Experiment: BESIII (BEPC)

Inspire ID: 2016785

Status: VALIDATED NOHEPDATA

Authors: - Peter Richardson

References: - Phys.Rev.D 105 (2022) 7, 072002

Beams: * *

Beam energies: ANY

Run details: none listed

Measurement of the mass distributions in the decay J/ψ → γη^′η^′. 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_2022_I2016785.cc`

// -*- C++ -*-
#include "Rivet/Analysis.hh"
#include "Rivet/Projections/DecayedParticles.hh"
#include "Rivet/Projections/UnstableParticles.hh"

namespace Rivet {


  /// @brief J/psi -> gamma eta' eta'
  class BESIII_2022_I2016785 : public Analysis {
  public:

    /// Constructor
    RIVET_DEFAULT_ANALYSIS_CTOR(BESIII_2022_I2016785);


    /// @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);
      declare(psi, "psi");
      for (unsigned int ix = 0; ix < 2; ++ix) book(_h[ix], 1, 1, 1 + ix);
    }


    /// Perform the per-event analysis
    void analyze(const Event& event) {
      static const map<PdgId, unsigned int>& mode = {{331, 2}, {22, 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 Particles& eta = psi.decayProducts()[ix].at(331);
        const Particle& gamma = psi.decayProducts()[ix].at(22)[0];
        _h[0]->fill((eta[0].momentum() + eta[1].momentum()).mass());
        for (unsigned int ix = 0; ix < 2; ++ix) _h[1]->fill((gamma.momentum() + eta[ix].momentum()).mass());
      }
    }


    /// Normalise histograms etc., after the run
    void finalize() {
      for (unsigned int ix = 0; ix < 2; ++ix) normalize(_h[ix], 1., false);
    }

    /// @}


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


  RIVET_DECLARE_PLUGIN(BESIII_2022_I2016785);

}

Rivet analyses

Radiative J/ψ → γη′η′

Source code:BESIII_2022_I2016785.cc

Radiative J/ψ → γη^′η^′

Source code:`BESIII_2022_I2016785.cc`