Rivet analyses

title: BESIII_2021_I1859124

Dalitz plot analysis of $D^+\to K^+ K^0_S\pi^0$

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 $D^+\to K^+ K^0_S\pi^0$. 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++ // -- 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);

} ```