Rivet analyses

Mass distributions in the decays D0 → π+π−π+π− and D0 → K+K−π+π−

Experiment: CLEO (CESR)

Inspire ID: 1519168

Status: VALIDATED NOHEPDATA

Authors: - Peter Richardson

References: - JHEP 05 (2017) 143

Beams: * *

Beam energies: ANY

Run details: - Any process producing D0 mesons

Measurement of the mass distributions in the decays D0 → π+π−π+π− and D0 → K+K−π+π− using data from CLEO. 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:CLEO_2017_I1519168.cc

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

namespace Rivet {


  /// @brief D0 -> K+ K- pi+ pi- and 2pi+2pi-
  class CLEO_2017_I1519168 : public Analysis {
  public:

    /// Constructor
    RIVET_DEFAULT_ANALYSIS_CTOR(CLEO_2017_I1519168);


    /// @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<8;++ix)
    book(_h[ix   ],1,1,1+ix);
      for(unsigned int ix=0;ix<6;++ix)
    book(_h[ix+ 8],2,1,1+ix);
      for(unsigned int ix=0;ix<4;++ix)
    book(_h[ix+14],3,1,1+ix);
    }


    /// Perform the per-event analysis
    void analyze(const Event& event) {
      // define the decay mode
      static const map<PdgId,unsigned int> & mode1   = { { 211,2}, { -211,2}};
      static const map<PdgId,unsigned int> & mode2   = { { 321,1}, { -321,1}, { 211,1}, { -211,1}};
      DecayedParticles D0 = apply<DecayedParticles>(event, "D0");
      // loop over particles
      for(unsigned int ix=0;ix<D0.decaying().size();++ix) {
    int sign = D0.decaying()[ix].pid()/421;
    if ( D0.modeMatches(ix,4,mode1)) {
      const Particles & pip= D0.decayProducts()[ix].at( sign*211);
      const Particles & pim= D0.decayProducts()[ix].at(-sign*211);
      bool KSveto=false;
      set<double> mpm; 
      for(unsigned int ix=0;ix<2;++ix) {
        for(unsigned int iy=0;iy<2;++iy) {
          double m2 = (pip[ix].momentum()+pim[iy].momentum()).mass2();
          double m = sqrt(m2);
          mpm.insert(m2);
          if(abs(m-0.497611)<0.0165) KSveto=true;
        }
      }
      if(KSveto) continue;
      _h[0]->fill(*mpm.begin());
      _h[1]->fill(*mpm.rbegin());
      for(const double & m2 : mpm) _h[2]->fill(m2);
      FourMomentum ppp = pip[0].momentum()+pip[1].momentum();
      _h[3]->fill(ppp.mass2());
      FourMomentum pmm = pim[0].momentum()+pim[1].momentum();
      double m2ppm[2] = {(ppp+pim[0].momentum()).mass2(),(ppp+pim[1].momentum()).mass2()};
      if(m2ppm[0]>m2ppm[1]) swap(m2ppm[0],m2ppm[1]);
      _h[4]->fill(m2ppm[0]);
      _h[5]->fill(m2ppm[1]);
      double m2mmp[2] = {(pmm+pip[0].momentum()).mass2(),(pmm+pip[1].momentum()).mass2()};
      if(m2mmp[0]>m2mmp[1]) swap(m2mmp[0],m2mmp[1]);
      _h[6]->fill(m2mmp[0]);
      _h[7]->fill(m2ppm[1]);
    }
    else if ( D0.modeMatches(ix,4,mode2)) {
      const Particles & Kp = D0.decayProducts()[ix].at( sign*321);
      const Particles & Km = D0.decayProducts()[ix].at(-sign*321);
      const Particles & pip= D0.decayProducts()[ix].at( sign*211);
      const Particles & pim= D0.decayProducts()[ix].at(-sign*211);
      double mpipi = (pip[0].momentum()+pim[0].momentum()).mass();
      if(abs(mpipi-0.497611)<0.0165) continue;
      _h[ 8]->fill((Kp [0].momentum()+Km [0].momentum()).mass2());
      _h[ 9]->fill((Kp [0].momentum()+pip[0].momentum()).mass2());
      _h[10]->fill((Kp [0].momentum()+pim[0].momentum()).mass2());
      _h[11]->fill((Km [0].momentum()+pip[0].momentum()).mass2());
      _h[12]->fill((Km [0].momentum()+pim[0].momentum()).mass2());
      _h[13]->fill(sqr(mpipi));
      _h[14]->fill((Kp [0].momentum()+Km [0].momentum()+pip[0].momentum()).mass2());
      _h[15]->fill((Kp [0].momentum()+Km [0].momentum()+pim[0].momentum()).mass2());
      _h[16]->fill((Kp [0].momentum()+pip[0].momentum()+pim[0].momentum()).mass2());
      _h[17]->fill((Km [0].momentum()+pip[0].momentum()+pim[0].momentum()).mass2());
    }
      }
    }


    /// Normalise histograms etc., after the run
    void finalize() {
      for(unsigned int ix=0;ix<18;++ix)
    normalize(_h[ix],1.,false);
    }

    /// @}


    /// @name Histograms
    /// @{
    Histo1DPtr _h[18];
    /// @}


  };


  RIVET_DECLARE_PLUGIN(CLEO_2017_I1519168);

}