Rivet analyses

title: BESIII_2022_I2166668

$\chi_{cJ}\to \Lambda\bar\Lambda^0\eta$ decays

Experiment: BESIII (BEPC)

Inspire ID: 2166668

Status: VALIDATED NOHEPDATA

Authors: - Peter Richardson

References: - Phys.Rev.D 106 (2022) 7, 072004

Beams: * *

Beam energies: ANY

Run details: - Any process producing chi_cJ, originally e+e-

Measurements of mass distributions in $\chi_{cJ}\to \Lambda\bar\Lambda^0\eta$ decays. The data were read from the plots in the paper and may not be corrected for efficiency but the background given in the paper has been subtracted.

Source code:BESIII_2022_I2166668.cc

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

include "Rivet/Analysis.hh"

include "Rivet/Projections/DecayedParticles.hh"

include "Rivet/Projections/UnstableParticles.hh"

namespace Rivet {

/// @brief chi_cJ -> Lambda Lambdabar0 eta class BESIII_2022_I2166668 : public Analysis { public:

/// Constructor
RIVET_DEFAULT_ANALYSIS_CTOR(BESIII_2022_I2166668);


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

/// Book histograms and initialise projections before the run
void init() {
  UnstableParticles ufs = UnstableParticles(Cuts::pid == 10441 or Cuts::pid == 20443 or Cuts::pid == 445);
  declare(ufs, "UFS");
  DecayedParticles chi(ufs);
  chi.addStable(PID::ETA);
  chi.addStable(PID::LAMBDA);
  chi.addStable(-PID::LAMBDA);
  declare(chi, "chi");
  // histos
  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) {
  static const map<PdgId, unsigned int>& mode = {{3122, 1}, {-3122, 1}, {221, 1}};
  DecayedParticles chi = apply<DecayedParticles>(event, "chi");
  for (unsigned int ix = 0; ix < chi.decaying().size(); ++ix) {
    if (!chi.modeMatches(ix, 3, mode)) continue;
    const Particle& lam = chi.decayProducts()[ix].at(3122)[0];
    const Particle& lamb = chi.decayProducts()[ix].at(-3122)[0];
    const Particle& eta = chi.decayProducts()[ix].at(221)[0];
    _h[0]->fill((lam.momentum() + lamb.momentum()).mass());
    _h[1]->fill((lam.momentum() + eta.momentum()).mass());
    _h[2]->fill((lamb.momentum() + eta.momentum()).mass());
  }
}


/// Normalise histograms etc., after the run
void finalize() {
  for (unsigned int ix = 0; ix < 3; ++ix) normalize(_h[ix], 1., false);
}

/// @}


/// @name Histograms
/// @{
Histo1DPtr _h[3];
/// @}

};

RIVET_DECLARE_PLUGIN(BESIII_2022_I2166668);

} ```