Rivet analyses

Dalitz plot analysis of D0 → π+π−π0

Experiment: CLEO (CESR)

Inspire ID: 679349

Status: VALIDATED NOHEPDATA

Authors: - Peter Richardson

References: - Phys.Rev.D 72 (2005) 031102

Beams: * *

Beam energies: ANY

Run details: - Any process producing D0 -> pi+pi-pi0, original e+e->Upsilon(4S)

Measurement of the mass distributions in the decay D0 → π+π−π0. The data were read from the plots in the paper. Resolution/acceptance effects have been not unfolded and given the agreement with the model in the paper this analysis should only be used for qualitative studies.

Source code:CLEO_2005_I679349.cc

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

namespace Rivet {


  /// @brief D0 -> pi+pi-pi0
  class CLEO_2005_I679349 : public Analysis {
  public:

    /// Constructor
    RIVET_DEFAULT_ANALYSIS_CTOR(CLEO_2005_I679349);


    /// @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::ETA);
      D0.addStable(PID::ETAPRIME);
      declare(D0, "D0");
      // histograms
      book(_h_pi[0],1,1,1);
      book(_h_pi[1],1,1,2);
      book(_h_pi[2],1,1,3);
      book(_dalitz, "dalitz",50,0.,3.2,50,0.0,3.2);
    }

    /// Perform the per-event analysis
    void analyze(const Event& event) {
      // define the decay mode
      static const map<PdgId,unsigned int> & mode   = { {211,1},{-211,1}, { 111,1}};
      DecayedParticles D0 = apply<DecayedParticles>(event, "D0");
      // loop over particles
      for(unsigned int ix=0;ix<D0.decaying().size();++ix) {
    if ( !D0.modeMatches(ix,3,mode) ) continue;
    int sign = D0.decaying()[ix].pid()/421;
    const Particles & pi0= D0.decayProducts()[ix].at( 111);
    const Particles & pip= D0.decayProducts()[ix].at( sign*211);
    const Particles & pim= D0.decayProducts()[ix].at(-sign*211);
    double mneut = (pim[0].momentum()+pip[0].momentum()).mass2();
    double mplus  = (pip[0].momentum()+pi0[0].momentum()).mass2();
    double mminus = (pim[0].momentum()+pi0[0].momentum()).mass2();
    _h_pi[0]->fill(mplus);
    _h_pi[1]->fill(mneut);
    _h_pi[2]->fill(mminus);
    _dalitz->fill(mneut,mplus);
      }
    }


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

    }

    /// @}


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


  };


  RIVET_DECLARE_PLUGIN(CLEO_2005_I679349);

}