Rivet analyses

title: BESIII_2022_I2166759

$J/\psi$ and $\psi(2S)$ decays to $\eta\Sigma^+\bar\Sigma^-$

Experiment: BESIII (BEPC)

Inspire ID: 2166759

Status: VALIDATED NOHEPDATA

Authors: - Peter Richardson

References: - arXiv: 210.09601

Beams: * *

Beam energies: ANY

Run details: - Any process producing J/psi or psi(2S), originally e+e-

Measurements of mass distributions in $J/\psi$ and $\psi(2S)$ decays to $\eta\Sigma^+\bar\Sigma^-$. 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_I2166759.cc

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

include "Rivet/Analysis.hh"

include "Rivet/Projections/DecayedParticles.hh"

include "Rivet/Projections/UnstableParticles.hh"

namespace Rivet {

/// @brief J/.psi anbd psi(2S) -> eta Sigma+ Sigmabar- class BESIII_2022_I2166759 : public Analysis { public:

/// Constructor
RIVET_DEFAULT_ANALYSIS_CTOR(BESIII_2022_I2166759);


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

/// Book histograms and initialise projections before the run
void init() {
  UnstableParticles ufs = UnstableParticles(Cuts::pid == 443 or Cuts::pid == 100443);
  declare(ufs, "UFS");
  DecayedParticles psi(ufs);
  psi.addStable(PID::ETA);
  psi.addStable(PID::SIGMAPLUS);
  psi.addStable(PID::SIGMAMINUS);
  psi.addStable(-PID::SIGMAPLUS);
  psi.addStable(-PID::SIGMAMINUS);
  declare(psi, "psi");
  // histos
  for (unsigned int ix = 0; ix < 6; ++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 = {{3222, 1}, {-3222, 1}, {221, 1}};
  DecayedParticles psi = apply<DecayedParticles>(event, "psi");
  for (unsigned int ix = 0; ix < psi.decaying().size(); ++ix) {
    if (!psi.modeMatches(ix, 3, mode)) continue;
    unsigned int ioff = psi.decaying()[ix].pid() == 443 ? 0 : 3;
    const Particle& sigp = psi.decayProducts()[ix].at(3222)[0];
    const Particle& sigm = psi.decayProducts()[ix].at(-3222)[0];
    const Particle& eta = psi.decayProducts()[ix].at(221)[0];
    _h[ioff + 0]->fill((sigp.momentum() + eta.momentum()).mass());
    _h[ioff + 1]->fill((sigm.momentum() + eta.momentum()).mass());
    _h[ioff + 2]->fill((sigp.momentum() + sigm.momentum()).mass());
  }
}


/// Normalise histograms etc., after the run
void finalize() {
  for (unsigned int ix = 0; ix < 6; ++ix) normalize(_h[ix], 1., false);
}

/// @}


/// @name Histograms
/// @{
Histo1DPtr _h[6];
/// @}

};

RIVET_DECLARE_PLUGIN(BESIII_2022_I2166759);

} ```