Rivet analyses

title: BESIII_2023_I2702517

$\psi(2S)\to \Lambda \bar{\Lambda}\eta^\prime$

Experiment: BESIII (BEPC)

Inspire ID: 2702517

Status: VALIDATED NOHEPDATA

Authors: - Peter Richardson

References: - arXiv: 2309.13790

Beams: * *

Beam energies: ANY

Run details: - Any process producing psi(2S) originally e+e-

Measurement of the mass distributions in the decay $\psi(2S)\to \Lambda \bar{\Lambda}\eta^\prime$. 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_I2702517.cc

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

include "Rivet/Analysis.hh"

include "Rivet/Projections/DecayedParticles.hh"

include "Rivet/Projections/UnstableParticles.hh"

namespace Rivet {

/// @brief psi(2S) -> Lambda Lambdabar eta' class BESIII_2023_I2702517 : public Analysis { public:

/// Constructor
RIVET_DEFAULT_ANALYSIS_CTOR(BESIII_2023_I2702517);


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

/// Book histograms and initialise projections before the run
void init() {
  UnstableParticles ufs = UnstableParticles(Cuts::pid == 100443);
  declare(ufs, "UFS");
  DecayedParticles psi(ufs);
  psi.addStable(PID::PI0);
  psi.addStable(PID::K0S);
  psi.addStable(PID::ETA);
  psi.addStable(PID::ETAPRIME);
  psi.addStable(PID::OMEGA);
  psi.addStable(3122);
  psi.addStable(-3122);
  declare(psi, "psi");
  for (unsigned int ix = 0; ix < 2; ++ix) {
    for (unsigned int iy = 0; iy < 2; ++iy) {
      book(_h[ix][iy], 1 + ix, 1, 1 + iy);
    }
  }
}


/// Perform the per-event analysis
void analyze(const Event& event) {
  DecayedParticles psi = apply<DecayedParticles>(event, "psi");
  // loop over particles
  for (unsigned int ix = 0; ix < psi.decaying().size(); ++ix) {
    if (!psi.modeMatches(ix, 3, mode)) continue;
    const Particle& eta = psi.decayProducts()[ix].at(331)[0];
    const Particle& lam = psi.decayProducts()[ix].at(3122)[0];
    const Particle& lbar = psi.decayProducts()[ix].at(-3122)[0];
    for (unsigned int iy = 0; iy < 2; ++iy) {
      _h[0][iy]->fill((lbar.mom() + eta.mom()).mass());
      _h[0][iy]->fill((lam.mom() + eta.mom()).mass());
      _h[1][iy]->fill((lam.mom() + lbar.mom()).mass());
    }
  }
}


/// Normalise histograms etc., after the run
void finalize() {
  for (unsigned int ix = 0; ix < 2; ++ix) {
    normalize(_h[ix], 1., false);
  }
}

/// @}


/// @name Histograms
/// @{
Histo1DPtr _h[2][2];
const map<PdgId, unsigned int> mode = {{3122, 1}, {-3122, 1}, {331, 1}};
/// @}

};

RIVET_DECLARE_PLUGIN(BESIII_2023_I2702517);

} ```