Rivet analyses

title: BES_1998_I482964

Mass distributions in $J/\psi\to\gamma K^+K^-\pi^0$

Experiment: BES (BEPC)

Inspire ID: 482964

Status: VALIDATED NOHEPDATA

Authors: - Peter Richardson

References: - Phys.Lett.B 440 (1998) 217-224

Beams: * *

Beam energies: ANY

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

Measurement of mass distributions in $J/\psi\to\gamma K^+K^-\pi^0$. The data were read from the plots in the paper and are not corrected.

Source code:BES_1998_I482964.cc

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

include "Rivet/Analysis.hh"

include "Rivet/Projections/DecayedParticles.hh"

include "Rivet/Projections/UnstableParticles.hh"

namespace Rivet {

/// @brief J/psi -> gamma K+K-pi0 class BES_1998_I482964 : public Analysis { public:

/// Constructor
RIVET_DEFAULT_ANALYSIS_CTOR(BES_1998_I482964);


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

/// Book histograms and initialise projections before the run
void init() {
  // Initialise and register projections
  UnstableParticles ufs = UnstableParticles(Cuts::abspid == 443);
  declare(ufs, "UFS");
  DecayedParticles PSI(ufs);
  PSI.addStable(PID::K0S);
  PSI.addStable(PID::PI0);
  declare(PSI, "PSI");
  // 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) {
  // find the J/psi decays
  static const map<PdgId, unsigned int>& mode1 = {{321, 1}, {321, 1}, {111, 1}, {22, 1}};
  DecayedParticles PSI = apply<DecayedParticles>(event, "PSI");
  // loop over particles
  for (unsigned int ix = 0; ix < PSI.decaying().size(); ++ix) {
    if (!PSI.modeMatches(ix, 4, mode1)) continue;
    const Particle& Kp = PSI.decayProducts()[0].at(321)[0];
    const Particle& Km = PSI.decayProducts()[0].at(-321)[0];
    const Particle& pi0 = PSI.decayProducts()[0].at(111)[0];
    FourMomentum pKK = Kp.mom() + Km.mom();
    _h[0]->fill((pKK + pi0.mom()).mass() / GeV);
    _h[1]->fill((Kp.mom() + pi0.mom()).mass() / GeV);
    _h[1]->fill((Km.mom() + pi0.mom()).mass() / GeV);
    _h[2]->fill(pKK.mass() / GeV);
  }
}


/// Normalise histograms etc., after the run
void finalize() {
  normalize(_h, 1.0, false);
}

/// @}


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

};

RIVET_DECLARE_PLUGIN(BES_1998_I482964);

} ```