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BESIII_2024_I2730532

Mass distributions for $D^0\to2\pi^+2\pi^-$ and $\pi^+\pi^-2\pi^0$
Experiment: BESIII (BEPC)
Inspire ID: 2730532
Status: VALIDATED NOHEPDATA
Authors:
  • Peter Richardson
References: Beams: * *
Beam energies: ANY
Run details:
  • Any process producing D0 mesons, originally e+e-

Mass distributions for $D^0\to2\pi^+2\pi^-$ and $\pi^+\pi^-2\pi^0$.

Source code: BESIII_2024_I2730532.cc
  1// -*- C++ -*-
  2#include "Rivet/Analysis.hh"
  3#include "Rivet/Projections/UnstableParticles.hh"
  4#include "Rivet/Projections/DecayedParticles.hh"
  5
  6namespace Rivet {
  7
  8
  9  /// @brief D0 -> 4 pions
 10  class BESIII_2024_I2730532 : public Analysis {
 11  public:
 12
 13    /// Constructor
 14    RIVET_DEFAULT_ANALYSIS_CTOR(BESIII_2024_I2730532);
 15
 16    /// @name Analysis methods
 17    /// @{
 18
 19    /// Book histograms and initialise projections before the run
 20    void init() {
 21      // Initialise and register projections
 22      UnstableParticles ufs = UnstableParticles(Cuts::abspid==421);
 23      declare(ufs, "UFS");
 24      DecayedParticles D0(ufs);
 25      D0.addStable(PID::PI0);
 26      D0.addStable(PID::K0S);
 27      D0.addStable(PID::ETA);
 28      D0.addStable(PID::ETAPRIME);
 29      declare(D0, "D0");
 30      for(unsigned int ix=0;ix<7;++ix) {
 31        book(_h_0[ix],2,1,1+ix);
 32        if(ix>=3) continue;
 33        book(_h_c[ix],1,1,1+ix);
 34      }
 35    }
 36
 37    /// Perform the per-event analysis
 38    void analyze(const Event& event) {
 39      // define the decay mode
 40      DecayedParticles D0 = apply<DecayedParticles>(event, "D0");
 41      // loop over particles
 42      for (unsigned int ix=0;ix<D0.decaying().size(); ++ix) {
 43      int sign = D0.decaying()[ix].pid()/421;
 44      if (D0.modeMatches(ix,4,mode1)) {
 45        const Particles & pip= D0.decayProducts()[ix].at( sign*211);
 46        const Particles & pim= D0.decayProducts()[ix].at(-sign*211);
 47        bool Kveto=false;
 48        set<double> mpm;
 49        for (unsigned int ix=0;ix<2;++ix) {
 50          if((pim[0].mom()+pim[1].mom()+pip[ix].mom()).mass()<0.51) continue;
 51          for(unsigned int iy=0;iy<2;++iy) {
 52            double m = (pip[ix].mom()+pim[iy].mom()).mass();
 53            mpm.insert(m);
 54            if(abs(m-.4976)<0.03) Kveto=true;
 55          }
 56        }
 57        if (Kveto) continue;
 58        for (const double& m : mpm) _h_c[0]->fill(m);
 59          for (unsigned int ix=0;ix<2;++ix) {
 60            _h_c[1]->fill((D0.decaying()[ix].mom()-pim[ix].mom()).mass());
 61            _h_c[2]->fill((D0.decaying()[ix].mom()-pip[ix].mom()).mass());
 62          }
 63        }
 64        else if (D0.modeMatches(ix,4,mode2)) {
 65          const Particles& pi0= D0.decayProducts()[ix].at(      111);
 66          const Particle & pip= D0.decayProducts()[ix].at( sign*211)[0];
 67          const Particle & pim= D0.decayProducts()[ix].at(-sign*211)[0];
 68          double m00 = (pi0[0].mom()+pi0[1].mom()).mass();
 69          if (m00>0.4376&&m00<5276) continue;
 70          double mpm =  (pip.mom()+pim.mom()).mass();
 71          if (abs(mpm-.4976)<0.03) continue;
 72          double mp0[2],mm0[2],mpm0[2];
 73          bool veto=false;
 74          for (unsigned int ix=0;ix<2;++ix) {
 75            mp0[ix] = (pi0[ix].mom()+pip.mom()).mass();
 76            mm0[ix] = (pi0[ix].mom()+pim.mom()).mass();
 77            if (mm0[ix]>0.4677&&mm0[ix]<.5067) veto=true;
 78            mpm0[ix] = (pi0[ix].mom()+pim.mom()+pip.mom()).mass();
 79            if (mpm0[ix]<.57) veto=true;
 80          }
 81          if (veto) continue;
 82          for (unsigned int ix=0;ix<2;++ix) {
 83            _h_0[0]->fill(mpm0[ix]);
 84            _h_0[5]->fill(mp0[ix]);
 85            _h_0[6]->fill(mm0[ix]);
 86          }
 87          _h_0[1]->fill((pi0[0].mom()+pi0[1].mom()+pip.mom()).mass());
 88          _h_0[2]->fill((pi0[0].mom()+pi0[1].mom()+pim.mom()).mass());
 89          _h_0[3]->fill(mpm);
 90          _h_0[4]->fill(m00);
 91        }
 92      }
 93    }
 94
 95    /// Normalise histograms etc., after the run
 96    void finalize() {
 97      normalize(_h_c);
 98      normalize(_h_0);
 99    }
100    /// @}
101
102    /// @name Histograms
103    /// @{
104    Histo1DPtr _h_c[3],_h_0[7];
105    const map<PdgId,unsigned int> mode1 = { { 211,2}, { -211,2}};
106    const map<PdgId,unsigned int> mode2 = { { 111,2}, { 211,1}, { -211,1}};
107    /// @}
108
109  };
110
111
112  RIVET_DECLARE_PLUGIN(BESIII_2024_I2730532);
113
114}