Rivet analyses

title: BESIII_2023_I2696635

Dalitz decay $D^+\to K^0_S\pi^+\eta$

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

} ```