Rivet analyses

Dalitz plot analysis of D0 → KS0K+K−

Experiment: BESIII (BEPC)

Inspire ID: 1799437

Status: VALIDATED NOHEPDATA

Authors: - Peter Richardson

References: - arXiv: 2006.02800

Beams: * *

Beam energies: ANY

Run details: - Any process producing D0

Measurement of Kinematic distributions in the decay D0 → KS0K+K− by BES. The data were read from the plots in the paper. Resolution/acceptance effects have been not unfolded. Given the agreement with the model in the paper this analysis should only be used for qualitative studies.

Source code:BESIII_2020_I1799437.cc

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

namespace Rivet {


  /// @brief D0 -> K_S0 K+ K-
  class BESIII_2020_I1799437 : public Analysis {
  public:

    /// Constructor
    RIVET_DEFAULT_ANALYSIS_CTOR(BESIII_2020_I1799437);


    /// @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
      book(_h_K0Km, 1, 1, 3);
      book(_h_K0Kp, 1, 1, 2);
      book(_h_KpKm, 1, 1, 1);
      book(_dalitz, "dalitz", 50, 0.9, 1.9, 50, 0.9, 1.9);
    }

    /// Perform the per-event analysis
    void analyze(const Event& event) {
      static const map<PdgId, unsigned int>& mode = {{321, 1}, {-321, 1}, {310, 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& K0 = D0.decayProducts()[ix].at(310);
        const Particles& Kp = D0.decayProducts()[ix].at(sign * 321);
        const Particles& Km = D0.decayProducts()[ix].at(-sign * 321);
        double mminus = (Km[0].momentum() + K0[0].momentum()).mass2();
        double mplus = (Kp[0].momentum() + K0[0].momentum()).mass2();
        double mKK = (Kp[0].momentum() + Km[0].momentum()).mass2();
        _h_K0Kp->fill(mplus);
        _h_K0Km->fill(mminus);
        _h_KpKm->fill(mKK);
        _dalitz->fill(mKK, mplus);
      }
    }


    /// Normalise histograms etc., after the run
    void finalize() {
      normalize(_h_K0Km);
      normalize(_h_K0Kp);
      normalize(_h_KpKm);
      normalize(_dalitz);
    }

    /// @}


    /// @name Histograms
    /// @{
    Histo1DPtr _h_K0Km, _h_KpKm, _h_K0Kp;
    Histo2DPtr _dalitz;
    /// @}
  };


  RIVET_DECLARE_PLUGIN(BESIII_2020_I1799437);

}