Rivet analyses

Mass distributions in J/ψ and ψ(2S) to π⁺π⁻π⁰

Experiment: BESIII (BEPC)

Inspire ID: 1088606

Status: VALIDATED NOHEPDATA

Authors: - Peter Richardson

References: - Phys.Lett.B 710 (2012) 594-599

Beams: * *

Beam energies: ANY

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

Measurement of the ππ mass distribution in the decays J/ψ and ψ(2S) to π⁺π⁻π⁰ be BES. N.B. data read from plots and may not be corrected.

Source code:`BESIII_2012_I1088606.cc`

// -*- C++ -*-
#include "Rivet/Analysis.hh"
#include "Rivet/Projections/DecayedParticles.hh"
#include "Rivet/Projections/UnstableParticles.hh"

namespace Rivet {


  /// @brief J/psi and psi(2S) -> pi+pi-pi0
  class BESIII_2012_I1088606 : public Analysis {
  public:

    /// Constructor
    RIVET_DEFAULT_ANALYSIS_CTOR(BESIII_2012_I1088606);


    /// @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::PI0);
      psi.addStable(PID::K0S);
      psi.addStable(PID::ETA);
      psi.addStable(PID::ETAPRIME);
      declare(psi, "psi");
      book(_h_pipi[0], 1, 1, 1);
      book(_h_pipi[1], 1, 1, 2);
      book(_dalitz[0], "dalitz_Jpsi", 50, 0., 9., 50, 0.0, 9.);
      book(_dalitz[1], "dalitz_psi2S", 50, 0., 14., 50, 0.0, 14.);
    }

    /// Perform the per-event analysis
    void analyze(const Event& event) {
      static const map<PdgId, unsigned int>& mode = {{211, 1}, {-211, 1}, {111, 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& pi0 = psi.decayProducts()[ix].at(111);
        const Particles& pip = psi.decayProducts()[ix].at(211);
        const Particles& pim = psi.decayProducts()[ix].at(-211);
        double mminus = (pim[0].momentum() + pi0[0].momentum()).mass2();
        double mplus = (pip[0].momentum() + pi0[0].momentum()).mass2();
        double mneut = (pip[0].momentum() + pim[0].momentum()).mass2();
        unsigned int iloc = psi.decaying()[ix].pid() / 100000;
        _h_pipi[iloc]->fill(sqrt(mneut));
        _h_pipi[iloc]->fill(sqrt(mplus));
        _h_pipi[iloc]->fill(sqrt(mminus));
        _dalitz[iloc]->fill(mplus, mminus);
      }
    }


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

    /// @}


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


  RIVET_DECLARE_PLUGIN(BESIII_2012_I1088606);

}

Rivet analyses

Mass distributions in J/ψ and ψ(2S) to π+π−π0

Source code:BESIII_2012_I1088606.cc

Mass distributions in J/ψ and ψ(2S) to π⁺π⁻π⁰

Source code:`BESIII_2012_I1088606.cc`