Rivet analyses

χcJ → 4KS0

Experiment: BESIII (BEPC)

Inspire ID: 1716627

Status: VALIDATED NOHEPDATA

Authors: - Peter Richardson

References: - Phys.Rev.D 99 (2019) 5, 052008

Beams: * *

Beam energies: ANY

Run details: - Any process producing chi_c originally e+e-

Measurement of the mass distributions in the decays χcJ → 4KS0. The data were read from the plots in the paper and may not be corrected for efficiency or background.

Source code:BESIII_2019_I1716627.cc

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

namespace Rivet {


  /// @brief chi_cJ -> 4KS0
  class BESIII_2019_I1716627 : public Analysis {
  public:

    /// Constructor
    RIVET_DEFAULT_ANALYSIS_CTOR(BESIII_2019_I1716627);


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

    /// Book histograms and initialise projections before the run
    void init() {
      UnstableParticles ufs = UnstableParticles(Cuts::pid == 20443 or Cuts::pid == 445 or Cuts::pid == 10441);
      declare(ufs, "UFS");
      DecayedParticles chi(ufs);
      chi.addStable(PID::PI0);
      chi.addStable(PID::K0S);
      chi.addStable(PID::ETA);
      declare(chi, "chi");
      for (unsigned int iy = 0; iy < 2; ++iy) {
        book(_h[iy], 1, 1, 1 + iy);
      }
    }


    /// Perform the per-event analysis
    void analyze(const Event& event) {
      static const map<PdgId, unsigned int>& mode = {{310, 4}};
      DecayedParticles chi = apply<DecayedParticles>(event, "chi");
      // loop over particles
      for (unsigned int ix = 0; ix < chi.decaying().size(); ++ix) {
        if (!chi.modeMatches(ix, 4, mode)) continue;
        const Particles& K0 = chi.decayProducts()[ix].at(310);
        for (unsigned int iy = 0; iy < 4; ++iy) {
          _h[1]->fill((chi.decaying()[ix].momentum() - K0[iy].momentum()).mass());
          for (unsigned int iz = ix + 1; iz < 4; ++iz)
            _h[0]->fill((K0[ix].momentum() + K0[iz].momentum()).mass());
        }
      }
    }


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

    /// @}


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


  RIVET_DECLARE_PLUGIN(BESIII_2019_I1716627);

}