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BELLE_2020_I1785816

Dalitz decay of $D^0\to K^-\pi^+\eta$
Experiment: BELLE (KEKB)
Inspire ID: 1785816
Status: VALIDATED NOHEPDATA
Authors:
  • Peter Richardson
References:
  • Phys.Rev.D 102 (2020) 1, 012002
Beams: * *
Beam energies: ANY
Run details:
  • Any process producing D0 mesons

Measurement of the mass distributions in the decay $D^0\to K^-\pi^+\eta$ by BELLE. The data were read from the plots in the paper, and for many points the error bars are the size of the point. It is also not clear that any resolution effects have been unfolded.

Source code: BELLE_2020_I1785816.cc 
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// -*- C++ -*-
#include "Rivet/Analysis.hh"
#include "Rivet/Projections/UnstableParticles.hh"
#include "Rivet/Projections/DecayedParticles.hh"

namespace Rivet {


  /// @brief D0 -> K- pi+ eta
  class BELLE_2020_I1785816 : public Analysis {
  public:

    /// Constructor
    RIVET_DEFAULT_ANALYSIS_CTOR(BELLE_2020_I1785816);


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

    /// Book histograms and initialise projections before the run
    void init() {
      // Initialise and register projections
      UnstableParticles ufs = UnstableParticles(Cuts::abspid==421);
      declare(ufs, "UFS");
      DecayedParticles D0(ufs);
      D0.addStable(PID::PI0);
      D0.addStable(PID::K0S);
      D0.addStable(PID::ETA);
      D0.addStable(PID::ETAPRIME);
      declare(D0, "D0");
      // histograms
      book(_h_Kpi  ,1,1,1);
      book(_h_etapi,1,1,2);
      book(_h_Keta ,1,1,3);
      book(_dalitz, "dalitz",50,0.3,1.8,50,0.4,1.9);
    }

    /// Perform the per-event analysis
    void analyze(const Event& event) {
      static const map<PdgId,unsigned int> & mode   = { {-321,1},{ 211,1}, {221,1}};
      static const map<PdgId,unsigned int> & modeCC = { { 321,1},{-211,1}, {221,1}};
      DecayedParticles D0 = apply<DecayedParticles>(event, "D0");
      // loop over particles
      for(unsigned int ix=0;ix<D0.decaying().size();++ix) {
	int sign = 1;
	if (D0.decaying()[ix].pid()>0 && D0.modeMatches(ix,3,mode)) {
	  sign=1;
	}
	else if  (D0.decaying()[ix].pid()<0 && D0.modeMatches(ix,3,modeCC)) {
	  sign=-1;
	}
	else
	  continue;
	const Particles & eta= D0.decayProducts()[ix].at(221);
	const Particles & Km = D0.decayProducts()[ix].at(-sign*321);
	const Particles & pip= D0.decayProducts()[ix].at( sign*211);
	double metapi = (eta[0].momentum()+pip[0].momentum()).mass2();
	double metaK  = (eta[0].momentum()+ Km[0].momentum()).mass2();
	double mKpi   = ( Km[0].momentum()+pip[0].momentum()).mass2();
	_dalitz ->fill(mKpi,metapi);
	_h_etapi->fill(metapi);
	_h_Keta ->fill(metaK );
	_h_Kpi  ->fill(mKpi);
      }
    }


    /// Normalise histograms etc., after the run
    void finalize() {
      normalize(_h_Kpi  );
      normalize(_h_etapi);
      normalize(_h_Keta );
      normalize(_dalitz );
    }

    /// @}


    /// @name Histograms
    /// @{
    Histo1DPtr _h_Kpi,_h_etapi,_h_Keta;
    Histo2DPtr _dalitz;
    /// @}


  };


  RIVET_DECLARE_PLUGIN(BELLE_2020_I1785816);

}