Rivet analyses

Dalitz plot analysis of J/ψ → π+π−π0, K+K−π0 and KS0K±π∓

Experiment: BABAR (PEP-II)

Inspire ID: 1512302

Status: VALIDATED NOHEPDATA

Authors: - Peter Richardson

References: - Phys.Rev.D 95 (2017) 7, 072007

Beams: * *

Beam energies: ANY

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

Measurement of the mass distributions in the decays J/ψ → π+π−π0, K+K−π0 and KS0K±π∓ by BaBar. The data were read from the plots in the paper and therefore for some points the error bars are the size of the point. Also the sideband background from the plots has been subtracted. It is also not clear that any resolution effects have been unfolded.

Source code:BABAR_2017_I1512302.cc

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

namespace Rivet {


  /// @brief J/psi dalitz decays
  class BABAR_2017_I1512302 : public Analysis {
  public:

    /// Constructor
    RIVET_DEFAULT_ANALYSIS_CTOR(BABAR_2017_I1512302);


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

    /// Book histograms and initialise projections before the run
    void init() {
      // Initialise and register projections
      UnstableParticles ufs = UnstableParticles(Cuts::pid== 443);
      declare(ufs, "UFS");
      DecayedParticles PSI(ufs);
      PSI.addStable(PID::PI0);
      PSI.addStable(PID::K0S);
      declare(PSI,"PSI");
      // histos
      book(_h_pippim,1,1,1);
      book(_h_pippi0,1,1,2);
      book(_dalitz_3pi, "dalitz_3pi",50,0.,9.,50,0.0,9.);
      book(_h_KpKm ,2,1,1);
      book(_h_Kppi0,2,1,2);
      book(_dalitz_KpKmpi, "dalitz_KpKmpi",50,0.,7.,50,0.0,7.);
      book(_h_K0Kp ,3,1,1);
      book(_h_K0pip,3,1,2);
      book(_h_Kppip,3,1,3);
      book(_dalitz_K0Kppim, "dalitz_K0Kppim",50,0.,8.,50,0.,8.);
    }

    /// Perform the per-event analysis
    void analyze(const Event& event) {
      static const map<PdgId,unsigned int> & mode1   = { { 211,1},{-211,1}, {111,1}};
      static const map<PdgId,unsigned int> & mode2   = { { 321,1},{-321,1}, {111,1}};
      static const map<PdgId,unsigned int> & mode3   = { { 321,1},{-211,1}, {310,1}};
      static const map<PdgId,unsigned int> & mode3CC = { {-321,1},{ 211,1}, {310,1}};
      DecayedParticles PSI = apply<DecayedParticles>(event, "PSI");
      // loop over particles
      for(unsigned int ix=0;ix<PSI.decaying().size();++ix) {
    if (PSI.modeMatches(ix,3,mode1)) {
      const Particle & pip = PSI.decayProducts()[ix].at( 211)[0];
      const Particle & pim = PSI.decayProducts()[ix].at(-211)[0];
      const Particle & pi0 = PSI.decayProducts()[ix].at( 111)[0];
      double mminus = (pim.momentum()+pi0.momentum()).mass2();
      double mplus  = (pip.momentum()+pi0.momentum()).mass2();
      double mneut  = (pip.momentum()+pim.momentum()).mass2();
      _h_pippim->fill(mneut );
      _h_pippi0->fill(mplus );
      _h_pippi0->fill(mminus);
      _dalitz_3pi->fill(mplus,mminus);
    }
    else if (PSI.modeMatches(ix,3,mode2)) {
      const Particle & Kp  = PSI.decayProducts()[ix].at( 321)[0];
      const Particle & Km  = PSI.decayProducts()[ix].at(-321)[0];
      const Particle & pi0 = PSI.decayProducts()[ix].at( 111)[0];
      double mminus = (Km.momentum()+pi0.momentum()).mass2();
      double mplus  = (Kp.momentum()+pi0.momentum()).mass2();
      double mneut  = (Kp.momentum()+Km.momentum()).mass2();
      _h_KpKm->fill(mneut );
      _h_Kppi0->fill(mplus );
      _h_Kppi0->fill(mminus);
      _dalitz_KpKmpi->fill(mplus,mminus);
    }
    else {
      int sign =1;
      if     (PSI.modeMatches(ix,3,mode3  )) sign= 1;
      else if(PSI.modeMatches(ix,3,mode3CC)) sign=-1;
      else continue;
      const Particle & Kp  = PSI.decayProducts()[ix].at( sign*321)[0];
      const Particle & pim = PSI.decayProducts()[ix].at(-sign*211)[0];
      const Particle & K0  = PSI.decayProducts()[ix].at(      310)[0];
      double mplus  = (Kp.momentum()  +  K0.momentum()).mass2();
      double mminus = (K0.momentum()  + pim.momentum()).mass2();
      double mKK    = (Kp.momentum()  +  K0.momentum()).mass2();
      _h_K0Kp ->fill(mKK);
      _h_Kppip->fill(mplus);
      _h_K0pip->fill(mminus);
      _dalitz_K0Kppim->fill(mplus,mminus);
    }
      }
    }


    /// Normalise histograms etc., after the run
    void finalize() {
      normalize(_h_pippim,1.,false);
      normalize(_h_pippi0,1.,false);
      normalize(_dalitz_3pi);
      normalize(_h_KpKm,1.,false);
      normalize(_h_Kppi0,1.,false);
      normalize(_dalitz_KpKmpi);
      normalize(_h_Kppip);
      normalize(_h_K0pip);
      normalize(_h_K0Kp );
      normalize(_dalitz_K0Kppim);
    }

    /// @}


    /// @name Histograms
    /// @{
    Histo1DPtr _h_pippim,_h_pippi0;
    Histo2DPtr _dalitz_3pi;
    Histo1DPtr _h_KpKm,_h_Kppi0;
    Histo2DPtr _dalitz_KpKmpi;
    Histo1DPtr _h_Kppip,_h_K0pip,_h_K0Kp;
    Histo2DPtr _dalitz_K0Kppim;
    /// @}


  };


  RIVET_DECLARE_PLUGIN(BABAR_2017_I1512302);

}