Rivet analyses

Dalitz plot analysis of ηc → KS0K±π∓ and ηc → K+K−π0

Experiment: BABAR (PEP-II)

Inspire ID: 1403544

Status: VALIDATED

Authors: - Peter Richardson

References: - Phys.Rev.D 89 (2014) 11, 112004

Beams: * *

Beam energies: ANY

Run details: - Any process producing eta_c (originally gamma gamma -> eta_c)

Measurement of the mass distributions in the decays ηc → KS0K±π∓ and ηc → K+K−π0 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_2015_I1403544.cc

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

namespace Rivet {


  /// @brief eta_c -> K+K-pi0 KS0 K+-pi-+
  class BABAR_2015_I1403544 : public Analysis {
  public:

    /// Constructor
    RIVET_DEFAULT_ANALYSIS_CTOR(BABAR_2015_I1403544);


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

    /// Book histograms and initialise projections before the run
    void init() {
      // Initialise and register projections
      UnstableParticles ufs = UnstableParticles(Cuts::pid== 441);
      declare(ufs, "UFS");
      DecayedParticles ETAC(ufs);
      ETAC.addStable(PID::PI0);
      ETAC.addStable(PID::K0S);
      ETAC.addStable(PID::ETA);
      ETAC.addStable(PID::ETAPRIME);
      declare(ETAC,"ETAC");
      // histograms
      book(_h_Kppip,3,1,1);
      book(_h_K0pip,3,1,2);
      book(_h_K0Kp ,3,1,3);
      book(_dalitz[0], "dalitz_1",50,0.,8.,50,0.,8.);
      book(_h_Kppi0,4,1,1);
      book(_h_Kmpi0,4,1,2);
      book(_h_KpKm ,4,1,3);
      book(_dalitz[1], "dalitz_2",50,0.,8.,50,0.,8.);
    }

    /// Perform the per-event analysis
    void analyze(const Event& event) {
      static const map<PdgId,unsigned int> & mode1   = { { 321,1}, {-321,1}, { 111,1}};
      static const map<PdgId,unsigned int> & mode2   = { { 321,1}, {-211,1}, { 310,1}};
      static const map<PdgId,unsigned int> & mode2CC = { {-321,1}, { 211,1}, { 310,1}};
      DecayedParticles ETAC = apply<DecayedParticles>(event, "ETAC");
      // loop over particles
      for(unsigned int ix=0;ix<ETAC.decaying().size();++ix) {
    // K+ K- pi0
    if (ETAC.modeMatches(ix,3,mode1)&&
        ETAC.decaying()[ix].mass()>2.922 && ETAC.decaying()[ix].mass()<3.036) {
      const Particle & Kp  = ETAC.decayProducts()[ix].at( 321)[0];
      const Particle & Km  = ETAC.decayProducts()[ix].at(-321)[0];
      const Particle & pi0 = ETAC.decayProducts()[ix].at( 111)[0];
      double mplus  = (Kp.momentum()+pi0.momentum()).mass2();
      double mminus = (Km.momentum()+pi0.momentum()).mass2();
      double mKK    = (Kp.momentum()+Km .momentum()).mass2();
      _h_KpKm->fill(mKK);
      _h_Kppi0->fill(mplus);
      _h_Kmpi0->fill(mminus);
      _dalitz[1]->fill(mplus,mminus);
      continue;
    }
    else if(ETAC.decaying()[ix].mass()>2.922 && ETAC.decaying()[ix].mass()<3.039) {
      int sign=1;
      if     (ETAC.modeMatches(ix,3,mode2  )) sign= 1;
      else if(ETAC.modeMatches(ix,3,mode2CC)) sign=-1;
      else continue;
      const Particle & KS0 = ETAC.decayProducts()[ix].at( 310)[0];
      const Particle & Kp  = ETAC.decayProducts()[ix].at( sign*321)[0];
      const Particle & pim = ETAC.decayProducts()[ix].at(-sign*211)[0];
      double mplus  = (Kp.momentum()  + pim.momentum()).mass2();
      double mminus = (KS0.momentum() + pim.momentum()).mass2();
      double mKK    = (Kp.momentum()  + KS0.momentum()).mass2();
      _h_K0Kp ->fill(mKK);
      _h_Kppip->fill(mplus);
      _h_K0pip->fill(mminus);
      _dalitz[0]->fill(mplus,mminus);
    }
      }
    }


    /// Normalise histograms etc., after the run
    void finalize() {
      normalize(_h_Kppip);
      normalize(_h_K0pip);
      normalize(_h_K0Kp );
      normalize(_dalitz[0]);
      normalize(_h_Kppi0);
      normalize(_h_Kmpi0);
      normalize(_h_KpKm );
      normalize(_dalitz[1]);
    }

    /// @}


    /// @name Histograms
    /// @{
    Histo1DPtr _h_Kppip,_h_K0pip,_h_K0Kp;
    Histo1DPtr _h_Kppi0,_h_Kmpi0,_h_KpKm;
    Histo2DPtr _dalitz[2];
    /// @}


  };


  RIVET_DECLARE_PLUGIN(BABAR_2015_I1403544);

}