Rivet analyses

Mass distributions in the decay D0 → K−π+π0π0

Experiment: BESIII (BEPC)

Inspire ID: 1725265

Status: VALIDATED NOHEPDATA

Authors: - Peter Richardson

References: - Phys.Rev.D 99 (2019) 9, 092008

Beams: * *

Beam energies: ANY

Run details: - Any process producing D0 mesons

Measurement of the mass distributions in the decay D0 → K−π+π0π0 by BES. The data were read from the plots in the paper and therefore for some points the error bars are the size of the point. It is also not clear that any resolution effects have been unfolded.

Source code:BESIII_2019_I1725265.cc

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

namespace Rivet {


  /// @brief D0 -> K- pi+ pi0 pi0
  class BESIII_2019_I1725265 : public Analysis {
  public:

    /// Constructor
    RIVET_DEFAULT_ANALYSIS_CTOR(BESIII_2019_I1725265);


    /// @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
      for(unsigned int ix=0;ix<4;++ix)
    book(_h[ix],1,1,1+ix);
    }

    /// Perform the per-event analysis
    void analyze(const Event& event) {
      // define the decay mode
      static const map<PdgId,unsigned int> & mode   = { {-321,1},{ 211,1}, { 111,2}};
      static const map<PdgId,unsigned int> & modeCC = { { 321,1},{-211,1}, { 111,2}};
      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,4,mode)) {
      sign=1;
    }
    else if  (D0.decaying()[ix].pid()<0 && D0.modeMatches(ix,4,modeCC)) {
      sign=-1;
    }
    else
      continue;
    const Particles & pi0= D0.decayProducts()[ix].at(111);
    double mpipi = (pi0[0].momentum()+pi0[1].momentum()).mass();
    if (mpipi>.458 && mpipi<.52) continue;
    const Particles & Km = D0.decayProducts()[ix].at(-sign*321);
    const Particles & pip= D0.decayProducts()[ix].at( sign*211);
    _h[0]->fill((Km [0].momentum()+pip[0].momentum()).mass2());
    _h[1]->fill((Km [0].momentum()+pi0[0].momentum()).mass2());
    _h[1]->fill((Km [0].momentum()+pi0[1].momentum()).mass2());
    _h[2]->fill((pip[0].momentum()+pi0[0].momentum()).mass2());
    _h[2]->fill((pip[0].momentum()+pi0[1].momentum()).mass2());
    _h[3]->fill(sqr(mpipi));
      }
    }


    /// Normalise histograms etc., after the run
    void finalize() {
      for(unsigned int ix=0;ix<4;++ix)
    normalize(_h[ix],1.,false);
    }

    /// @}


    /// @name Histograms
    /// @{
    Histo1DPtr _h[4];
    /// @}


  };


  RIVET_DECLARE_PLUGIN(BESIII_2019_I1725265);

}