Rivet analyses

title: BES_2001_I556330

$J/\psi\to p \bar{p}\eta$

Experiment: BES (BEPC)

Inspire ID: 556330

Status: VALIDATED NOHEPDATA

Authors: - Peter Richardson

References: - Phys.Lett.B 510 (2001) 75-82

Beams: * *

Beam energies: ANY

Run details: - Any process producing J/psi originally e+e-

Measurement of the mass distributions in the decay $J/\psi\to p \bar{p}\eta$. The data were read from the plots in the paper and may not be corrected for detector efficiency or backgrounds.

Source code:BES_2001_I556330.cc

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

include "Rivet/Analysis.hh"

include "Rivet/Projections/DecayedParticles.hh"

include "Rivet/Projections/UnstableParticles.hh"

namespace Rivet {

/// @brief J/psi -> p pbar eta class BES_2001_I556330 : public Analysis { public:

/// Constructor
RIVET_DEFAULT_ANALYSIS_CTOR(BES_2001_I556330);


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

/// Book histograms and initialise projections before the run
void init() {
  UnstableParticles ufs = UnstableParticles(Cuts::pid == 443);
  declare(ufs, "UFS");
  DecayedParticles psi(ufs);
  psi.addStable(PID::PI0);
  psi.addStable(PID::K0S);
  psi.addStable(PID::ETA);
  psi.addStable(PID::ETAPRIME);
  declare(psi, "psi");
  for (unsigned int ix = 0; ix < 2; ++ix) book(_h[ix], 1 + ix, 1, 1);
  book(_dalitz, "dalitz", 50, 2., 5., 50, 2., 5.);
}


/// Perform the per-event analysis
void analyze(const Event& event) {
  static const map<PdgId, unsigned int>& mode = {{2212, 1}, {-2212, 1}, {221, 1}};
  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 Particles& eta = psi.decayProducts()[ix].at(221);
    const Particles& pp = psi.decayProducts()[ix].at(2212);
    const Particles& pbar = psi.decayProducts()[ix].at(-2212);
    double mminus = (pbar[0].momentum() + eta[0].momentum()).mass2();
    double mplus = (pp[0].momentum() + eta[0].momentum()).mass2();
    _h[0]->fill(sqrt(mplus));
    _h[0]->fill(sqrt(mminus));
    _h[1]->fill((pp[0].momentum() + pbar[0].momentum()).mass());
    _dalitz->fill(mplus, mminus);
  }
}


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

/// @}


/// @name Histograms
/// @{
Histo1DPtr _h[2];
Histo2DPtr _dalitz;
/// @}

};

RIVET_DECLARE_PLUGIN(BES_2001_I556330);

} ```