Rivet analyses

χc(0, 1, 2) → ϕϕη

Experiment: BESIII (BEPC)

Inspire ID: 1763897

Status: VALIDATED NOHEPDATA

Authors: - Peter Richardson

References: - Phys.Rev.D 101 (2020) 1, 012012

Beams: * *

Beam energies: ANY

Run details: - Any process producing chi_c originally e+e-

Measurement of the mass distributions in the decays χc(0, 1, 2) → ϕϕη. The data were read from the plots in the paper and may not be corrected for efficiency or background.

Source code:BESIII_2020_I1763897.cc

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

namespace Rivet {


  /// @brief chi_c -> phi phi eta
  class BESIII_2020_I1763897 : public Analysis {
  public:

    /// Constructor
    RIVET_DEFAULT_ANALYSIS_CTOR(BESIII_2020_I1763897);


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

    /// Book histograms and initialise projections before the run
    void init() {
      UnstableParticles ufs = UnstableParticles(Cuts::pid==20443 or
                        Cuts::pid==445   or
                        Cuts::pid==10441);
      declare(ufs, "UFS");
      DecayedParticles chi(ufs);
      chi.addStable( PID::PI0);
      chi.addStable( PID::K0S);
      chi.addStable( PID::ETA);
      chi.addStable( PID::ETAPRIME);
      chi.addStable( PID::PHI);
      declare(chi, "chi");
      for(unsigned int ix=0;ix<3;++ix) {
    book(_dalitz[ix], "dalitz_"+toString(ix+1),50,2.,7.,50,2.,7.);
    for(unsigned int iy=0;iy<2;++iy) {
      book(_h[ix][iy],1+ix,1,1+iy);
    }
      }
    }


    /// Perform the per-event analysis
    void analyze(const Event& event) {
      static const map<PdgId,unsigned int> & mode   = { {333,2}, {221,1}};
      DecayedParticles chi = apply<DecayedParticles>(event, "chi");
      // loop over particles
      for(unsigned int ix=0;ix<chi.decaying().size();++ix) {
    if(!chi.modeMatches(ix,3,mode)) continue;
    unsigned int iloc = chi.decaying()[ix].pid()==10441 ? 0 : chi.decaying()[ix].pid()==445 ? 2 : 1;
    const Particle  & eta = chi.decayProducts()[ix].at(221)[0];
    const Particles & phi = chi.decayProducts()[ix].at(333);
    _h[iloc][0]->fill((phi[0].momentum()+phi[1].momentum()).mass());
    double mPhiEta[2]={(phi[0].momentum()+eta.momentum()).mass2(),
               (phi[1].momentum()+eta.momentum()).mass2()};
    _h[iloc][1]->fill(sqrt(mPhiEta[0]));
    _h[iloc][1]->fill(sqrt(mPhiEta[1]));
    _dalitz[iloc]->fill(mPhiEta[0],mPhiEta[1]);
    _dalitz[iloc]->fill(mPhiEta[1],mPhiEta[0]);
      }
    }


    /// Normalise histograms etc., after the run
    void finalize() {
      for(unsigned int ix=0;ix<3;++ix) {
    normalize(_dalitz[ix]);
    for(unsigned int iy=0;iy<2;++iy) {
      normalize(_h[ix][iy],1.,false);
    }
      }
    }

    /// @}


    /// @name Histograms
    /// @{
    Histo1DPtr _h[3][2];
    Histo2DPtr _dalitz[3];
    /// @}


  };


  RIVET_DECLARE_PLUGIN(BESIII_2020_I1763897);

}