Rivet analyses

title: BESIII_2019_I1716627

$\chi_{cJ}\to 4K^0_S$

Experiment: BESIII (BEPC)

Inspire ID: 1716627

Status: VALIDATED NOHEPDATA

Authors: - Peter Richardson

References: - Phys.Rev.D 99 (2019) 5, 052008

Beams: * *

Beam energies: ANY

Run details: - Any process producing chi_c originally e+e-

Measurement of the mass distributions in the decays $\chi_{cJ}\to 4K^0_S$. The data were read from the plots in the paper and may not be corrected for efficiency or background.

Source code:BESIII_2019_I1716627.cc

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

include "Rivet/Analysis.hh"

include "Rivet/Projections/DecayedParticles.hh"

include "Rivet/Projections/UnstableParticles.hh"

namespace Rivet {

/// @brief chi_cJ -> 4KS0 class BESIII_2019_I1716627 : public Analysis { public:

/// Constructor
RIVET_DEFAULT_ANALYSIS_CTOR(BESIII_2019_I1716627);


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

/// Book histograms and initialise projections before the run
void init() {
  UnstableParticles ufs = UnstableParticles(Cuts::pid == 20443 or Cuts::pid == 445 or Cuts::pid == 10441);
  declare(ufs, "UFS");
  DecayedParticles chi(ufs);
  chi.addStable(PID::PI0);
  chi.addStable(PID::K0S);
  chi.addStable(PID::ETA);
  declare(chi, "chi");
  for (unsigned int iy = 0; iy < 2; ++iy) {
    book(_h[iy], 1, 1, 1 + iy);
  }
}


/// Perform the per-event analysis
void analyze(const Event& event) {
  static const map<PdgId, unsigned int>& mode = {{310, 4}};
  DecayedParticles chi = apply<DecayedParticles>(event, "chi");
  // loop over particles
  for (unsigned int ix = 0; ix < chi.decaying().size(); ++ix) {
    if (!chi.modeMatches(ix, 4, mode)) continue;
    const Particles& K0 = chi.decayProducts()[ix].at(310);
    for (unsigned int iy = 0; iy < 4; ++iy) {
      _h[1]->fill((chi.decaying()[ix].momentum() - K0[iy].momentum()).mass());
      for (unsigned int iz = ix + 1; iz < 4; ++iz)
        _h[0]->fill((K0[ix].momentum() + K0[iz].momentum()).mass());
    }
  }
}


/// Normalise histograms etc., after the run
void finalize() {
  for (unsigned int iy = 0; iy < 2; ++iy) {
    normalize(_h[iy]);
  }
}

/// @}


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

};

RIVET_DECLARE_PLUGIN(BESIII_2019_I1716627);

} ```