Rivet analyses

Dalitz decay D+ → KS0π+η

Experiment: BESIII (BEPC)

Inspire ID: 2696635

Status: VALIDATED NOHEPDATA

Authors: - Peter Richardson

References: - arXiv: 2309.05760

Beams: * *

Beam energies: ANY

Run details: - Any process producing D+ mesons

Measurement of the mass distributions in the decay D+ → KS0π+η by BES. The data were read from the plots in the paper. It is also not clear that any resolution effects have been unfolded.

Source code:BESIII_2023_I2696635.cc

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

namespace Rivet {


  /// @brief D+ -> K0S pi+ eta
  class BESIII_2023_I2696635 : public Analysis {
  public:

    /// Constructor
    RIVET_DEFAULT_ANALYSIS_CTOR(BESIII_2023_I2696635);


    /// @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);
      DP.addStable(PID::ETA);
      declare(DP, "DP");
      // histograms#
      for (unsigned int ix = 0; ix < 3; ++ix) {
        book(_h[ix], 1, 1, 1 + ix);
      }
    }


    /// Perform the per-event analysis
    void analyze(const Event& event) {
      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& pip = DP.decayProducts()[ix].at(sign * 211)[0];
        const Particle& KS0 = DP.decayProducts()[ix].at(310)[0];
        const Particle& eta = DP.decayProducts()[ix].at(221)[0];
        _h[0]->fill((pip.mom() + KS0.mom()).mass() / GeV);
        _h[1]->fill((eta.mom() + KS0.mom()).mass() / GeV);
        _h[2]->fill((pip.mom() + eta.mom()).mass() / GeV);
      }
    }


    /// Normalise histograms etc., after the run
    void finalize() {
      normalize(_h, 1.0, false);
    }

    /// @}


    /// @name Histograms
    /// @{
    Histo1DPtr _h[3];
    const map<PdgId, unsigned int> mode = {{211, 1}, {310, 1}, {221, 1}};
    const map<PdgId, unsigned int> modeCC = {{-211, 1}, {310, 1}, {221, 1}};
    /// @}
  };


  RIVET_DECLARE_PLUGIN(BESIII_2023_I2696635);

}