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/UnstableParticles.hh"
#include "Rivet/Projections/DecayedParticles.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`