Rivet analyses

title: BESIII_2020_I1799437

Dalitz plot analysis of $D^0\to K^0_SK^+K^-$

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 $D^0\to K^0_SK^+K^-$ 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++ // -- 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);

} ```