Rivet analyses

Mass distributions in J/ψ → γK+K−π0

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/ψ → γK+K−π0. The data were read from the plots in the paper and are not corrected.

Source code:BES_1998_I482964.cc

// -*- 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);

}