Rivet analyses

Dalitz plot analysis of D+ → K+KS0π0

Experiment: BESIII (BEPC)

Inspire ID: 1859124

Status: VALIDATED NOHEPDATA

Authors: - Peter Richardson

References: - Phys.Rev.D 104 (2021) 012006

Beams: * *

Beam energies: ANY

Run details: - Any process producing D+ -> K+ KS0 pi0

Measurement of the mass distributions in the decay D+ → K+KS0π0. The data were read from the plots in the paper. Resolution/acceptance effects have been not unfolded and given the agreement with the model in the paper this analysis should only be used for qualitative studies.

Source code:BESIII_2021_I1859124.cc

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

namespace Rivet {


  /// @brief D+ -> K+ KS0 pi0
  class BESIII_2021_I1859124 : public Analysis {
  public:

    /// Constructor
    RIVET_DEFAULT_ANALYSIS_CTOR(BESIII_2021_I1859124);


    /// @name Analysis methods
    /// @{

    /// Book histograms and initialise projections before the run
    void init() {
      // Initialise and register projections
      UnstableParticles ufs = UnstableParticles(Cuts::abspid == 411);
      declare(ufs, "UFS");
      DecayedParticles DP(ufs);
      DP.addStable(PID::PI0);
      DP.addStable(PID::K0S);
      declare(DP, "DP");
      // histos
      book(_h_Kppi0, 1, 1, 1);
      book(_h_K0pi0, 1, 1, 2);
      book(_h_KpK0, 1, 1, 3);
      book(_dalitz, "dalitz", 50, 0.3, 2., 50, 0.3, 2.);
    }

    /// Perform the per-event analysis
    void analyze(const Event& event) {
      static const map<PdgId, unsigned int>& mode = {{321, 1}, {111, 1}, {310, 1}};
      static const map<PdgId, unsigned int>& modeCC = {{-321, 1}, {111, 1}, {310, 1}};
      DecayedParticles DP = apply<DecayedParticles>(event, "DP");
      // loop over particles
      for (unsigned int ix = 0; ix < DP.decaying().size(); ++ix) {
        int sign = 1;
        if (DP.decaying()[ix].pid() > 0 && DP.modeMatches(ix, 3, mode)) {
          sign = 1;
        }
        else if (DP.decaying()[ix].pid() < 0 && DP.modeMatches(ix, 3, modeCC)) {
          sign = -1;
        }
        else
          continue;
        const Particle& K0 = DP.decayProducts()[ix].at(310)[0];
        const Particle& pi0 = DP.decayProducts()[ix].at(111)[0];
        const Particle& Kp = DP.decayProducts()[ix].at(sign * 321)[0];
        double mplus = (Kp.momentum() + pi0.momentum()).mass2();
        double mneut = (K0.momentum() + pi0.momentum()).mass2();
        double mKK = (Kp.momentum() + K0.momentum()).mass2();
        _h_Kppi0->fill(sqrt(mplus));
        _h_K0pi0->fill(sqrt(mneut));
        _h_KpK0->fill(sqrt(mKK));
        _dalitz->fill(mplus, mneut);
      }
    }


    /// Normalise histograms etc., after the run
    void finalize() {
      normalize(_h_Kppi0);
      normalize(_h_K0pi0);
      normalize(_h_KpK0);
      normalize(_dalitz);
    }

    /// @}


    /// @name Histograms
    /// @{
    Histo1DPtr _h_Kppi0, _h_K0pi0, _h_KpK0;
    Histo2DPtr _dalitz;
    /// @}
  };


  RIVET_DECLARE_PLUGIN(BESIII_2021_I1859124);

}