Rivet analyses

Mass distributions in ψ(2S) → ωKS0KS0

Experiment: BESIII (BEPC)

Inspire ID: 1921801

Status: VALIDATED NOHEPDATA

Authors: - Peter Richardson

References: - Phys.Rev.D 104 (2021) 9, 092003

Beams: * *

Beam energies: ANY

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

Measurement of mass distributions in ψ(2S) → ωKS0KS0 by BES. N.B. data read from plots and may not be corrected, no difference between KS10 and KS20 so these are symeterised.

Source code:BESIII_2021_I1921801.cc

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

namespace Rivet {


  /// @brief psi(2S) -> omega KS0 KS0
  class BESIII_2021_I1921801 : public Analysis {
  public:

    /// Constructor
    RIVET_DEFAULT_ANALYSIS_CTOR(BESIII_2021_I1921801);


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

    /// Book histograms and initialise projections before the run
    void init() {
      // Initialise and register projections
      UnstableParticles ufs = UnstableParticles(Cuts::pid == 100443);
      declare(ufs, "UFS");
      DecayedParticles psi2S(ufs);
      psi2S.addStable(PID::PI0);
      psi2S.addStable(PID::K0S);
      psi2S.addStable(PID::ETA);
      psi2S.addStable(PID::ETAPRIME);
      psi2S.addStable(PID::OMEGA);
      declare(psi2S, "psi2S");
      // histograms
      for (unsigned int ix = 0; ix < 3; ++ix) book(_h[ix], 1, 1, 1 + ix);
      book(_dalitz, "dalitz", 50, 1., 11., 50, 1., 11.);
    }


    /// Perform the per-event analysis
    void analyze(const Event& event) {
      // define the decay mode
      static const map<PdgId, unsigned int>& mode = {{310, 2}, {223, 1}};
      DecayedParticles psi2S = apply<DecayedParticles>(event, "psi2S");
      // loop over particles
      for (unsigned int ix = 0; ix < psi2S.decaying().size(); ++ix) {
        if (!psi2S.modeMatches(ix, 3, mode)) continue;
        const Particles& K0 = psi2S.decayProducts()[ix].at(310);
        const Particles& omega = psi2S.decayProducts()[ix].at(223);
        double m2Komega[2] = {(K0[0].momentum() + omega[0].momentum()).mass2(),
                              (K0[1].momentum() + omega[0].momentum()).mass2()};
        for (unsigned int ix = 0; ix < 2; ++ix) {
          double mKo = sqrt(m2Komega[ix]);
          _h[0]->fill(mKo);
          _h[1]->fill(mKo);
        }
        _h[2]->fill((K0[0].momentum() + K0[1].momentum()).mass());
        _dalitz->fill(m2Komega[0], m2Komega[1]);
        _dalitz->fill(m2Komega[1], m2Komega[0]);
      }
    }


    /// Normalise histograms etc., after the run
    void finalize() {
      for (unsigned int ix = 0; ix < 3; ++ix) normalize(_h[ix], 1., false);
      normalize(_dalitz);
    }

    /// @}


    /// @name Histograms
    /// @{
    Histo1DPtr _h[3];
    Histo2DPtr _dalitz;
    /// @}
  };


  RIVET_DECLARE_PLUGIN(BESIII_2021_I1921801);

}