Rivet analyses

Mass distributions for D⁰ → 2π⁺2π⁻ and π⁺π⁻2π⁰

Experiment: BESIII (BEPC)

Inspire ID: 2730532

Status: VALIDATED NOHEPDATA

Authors: - Peter Richardson

References: - arXiv: 1605.03814’

Beams: * *

Beam energies: ANY

Run details: - Any process producing D0 mesons, originally e+e-

Mass distributions for D⁰ → 2π⁺2π⁻ and π⁺π⁻2π⁰.

Source code:`BESIII_2024_I2730532.cc`

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

namespace Rivet {


  /// @brief D0 -> 4 pions
  class BESIII_2024_I2730532 : public Analysis {
  public:

    /// Constructor
    RIVET_DEFAULT_ANALYSIS_CTOR(BESIII_2024_I2730532);

    /// @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");
      for (unsigned int ix = 0; ix < 7; ++ix) {
        book(_h_0[ix], 2, 1, 1 + ix);
        if (ix >= 3) continue;
        book(_h_c[ix], 1, 1, 1 + ix);
      }
    }

    /// Perform the per-event analysis
    void analyze(const Event& event) {
      // define the decay mode
      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 Kveto = false;
          set<double> mpm;
          for (unsigned int ix = 0; ix < 2; ++ix) {
            if ((pim[0].mom() + pim[1].mom() + pip[ix].mom()).mass() < 0.51) continue;
            for (unsigned int iy = 0; iy < 2; ++iy) {
              double m = (pip[ix].mom() + pim[iy].mom()).mass();
              mpm.insert(m);
              if (abs(m - .4976) < 0.03) Kveto = true;
            }
          }
          if (Kveto) continue;
          for (const double& m : mpm) _h_c[0]->fill(m);
          for (unsigned int ix = 0; ix < 2; ++ix) {
            _h_c[1]->fill((D0.decaying()[ix].mom() - pim[ix].mom()).mass());
            _h_c[2]->fill((D0.decaying()[ix].mom() - pip[ix].mom()).mass());
          }
        }
        else if (D0.modeMatches(ix, 4, mode2)) {
          const Particles& pi0 = D0.decayProducts()[ix].at(111);
          const Particle& pip = D0.decayProducts()[ix].at(sign * 211)[0];
          const Particle& pim = D0.decayProducts()[ix].at(-sign * 211)[0];
          double m00 = (pi0[0].mom() + pi0[1].mom()).mass();
          if (m00 > 0.4376 && m00 < 5276) continue;
          double mpm = (pip.mom() + pim.mom()).mass();
          if (abs(mpm - .4976) < 0.03) continue;
          double mp0[2], mm0[2], mpm0[2];
          bool veto = false;
          for (unsigned int ix = 0; ix < 2; ++ix) {
            mp0[ix] = (pi0[ix].mom() + pip.mom()).mass();
            mm0[ix] = (pi0[ix].mom() + pim.mom()).mass();
            if (mm0[ix] > 0.4677 && mm0[ix] < .5067) veto = true;
            mpm0[ix] = (pi0[ix].mom() + pim.mom() + pip.mom()).mass();
            if (mpm0[ix] < .57) veto = true;
          }
          if (veto) continue;
          for (unsigned int ix = 0; ix < 2; ++ix) {
            _h_0[0]->fill(mpm0[ix]);
            _h_0[5]->fill(mp0[ix]);
            _h_0[6]->fill(mm0[ix]);
          }
          _h_0[1]->fill((pi0[0].mom() + pi0[1].mom() + pip.mom()).mass());
          _h_0[2]->fill((pi0[0].mom() + pi0[1].mom() + pim.mom()).mass());
          _h_0[3]->fill(mpm);
          _h_0[4]->fill(m00);
        }
      }
    }

    /// Normalise histograms etc., after the run
    void finalize() {
      normalize(_h_c);
      normalize(_h_0);
    }
    /// @}

    /// @name Histograms
    /// @{
    Histo1DPtr _h_c[3], _h_0[7];
    const map<PdgId, unsigned int> mode1 = {{211, 2}, {-211, 2}};
    const map<PdgId, unsigned int> mode2 = {{111, 2}, {211, 1}, {-211, 1}};
    /// @}
  };


  RIVET_DECLARE_PLUGIN(BESIII_2024_I2730532);

}

Rivet analyses

Mass distributions for D0 → 2π+2π− and π+π−2π0

Source code:BESIII_2024_I2730532.cc

Mass distributions for D⁰ → 2π⁺2π⁻ and π⁺π⁻2π⁰

Source code:`BESIII_2024_I2730532.cc`