Rivet analyses

title: BESIII_2023_I2637232

$K^0_S$ momentum spectrum in $D\to K^0_SX$ decays

Experiment: BESIII (BEPC)

Inspire ID: 2637232

Status: VALIDATED NOHEPDATA

Authors: - Peter Richardson

References: - arXiv: 2302.14488

Beams: e+ e-

Beam energies: (1.9, 1.9)GeV

Run details: - e+e- to D Dbat at psi(3770)

Measurement of $K^0_S$ momentum spectrum in $D\to K^0_SX$ decays. The uncorrected data was read from the figures in the paper and the background given subtracted.

Source code:BESIII_2023_I2637232.cc

```c++ // -- C++ --

include "Rivet/Analysis.hh"

include "Rivet/Projections/UnstableParticles.hh"

namespace Rivet {

/// @brief D -> KS0 X class BESIII_2023_I2637232 : public Analysis { public:

/// Constructor
RIVET_DEFAULT_ANALYSIS_CTOR(BESIII_2023_I2637232);


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

/// Book histograms and initialise projections before the run
void init() {
  // projections
  declare(UnstableParticles(Cuts::pid == 30443), "UFS");
  // histos
  for (unsigned int ix = 0; ix < 2; ++ix) {
    book(_h[ix], 1, 1, 1 + ix);
  }
}

void findChildren(const Particle& p, Particles& K0) {
  for (const Particle& child : p.children()) {
    if (child.pid() == 310) {
      K0.push_back(child);
    }
    else if (!child.children().empty()) {
      findChildren(child, K0);
    }
  }
}

/// Perform the per-event analysis
void analyze(const Event& event) {
  const Particles& psi = apply<UnstableParticles>(event, "UFS").particles();
  if (psi.size() != 1) vetoEvent;
  for (const Particle& D : psi[0].children()) {
    int ih = -1;
    if (D.abspid() == 411)
      ih = 0;
    else if (D.abspid() == 421)
      ih = 1;
    else {
      continue;
    }
    Particles K0;
    findChildren(D, K0);
    for (const Particle& p : K0) {
      _h[ih]->fill(p.mom().p3().mod());
    }
  }
}


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

/// @}


/// @name Histograms
/// @{
Histo1DPtr _h[2];
/// @}

};

RIVET_DECLARE_PLUGIN(BESIII_2023_I2637232);

} ```