Rivet analyses

χc(0, 1, 2) → ϕϕη

Experiment: BESIII (BEPC)

Inspire ID: 1763897

Status: VALIDATED NOHEPDATA

Authors: - Peter Richardson

References: - Phys.Rev.D 101 (2020) 1, 012012

Beams: * *

Beam energies: ANY

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

Measurement of the mass distributions in the decays χc(0, 1, 2) → ϕϕη. The data were read from the plots in the paper and may not be corrected for efficiency or background.

Source code:BESIII_2020_I1763897.cc

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

namespace Rivet {


  /// @brief chi_c -> phi phi eta
  class BESIII_2020_I1763897 : public Analysis {
  public:

    /// Constructor
    RIVET_DEFAULT_ANALYSIS_CTOR(BESIII_2020_I1763897);


    /// @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);
      chi.addStable(PID::ETAPRIME);
      chi.addStable(PID::PHI);
      declare(chi, "chi");
      for (unsigned int ix = 0; ix < 3; ++ix) {
        book(_dalitz[ix], "dalitz_" + toString(ix + 1), 50, 2., 7., 50, 2., 7.);
        for (unsigned int iy = 0; iy < 2; ++iy) {
          book(_h[ix][iy], 1 + ix, 1, 1 + iy);
        }
      }
    }


    /// Perform the per-event analysis
    void analyze(const Event& event) {
      static const map<PdgId, unsigned int>& mode = {{333, 2}, {221, 1}};
      DecayedParticles chi = apply<DecayedParticles>(event, "chi");
      // loop over particles
      for (unsigned int ix = 0; ix < chi.decaying().size(); ++ix) {
        if (!chi.modeMatches(ix, 3, mode)) continue;
        unsigned int iloc = chi.decaying()[ix].pid() == 10441 ? 0 : chi.decaying()[ix].pid() == 445 ? 2 : 1;
        const Particle& eta = chi.decayProducts()[ix].at(221)[0];
        const Particles& phi = chi.decayProducts()[ix].at(333);
        _h[iloc][0]->fill((phi[0].momentum() + phi[1].momentum()).mass());
        double mPhiEta[2] = {(phi[0].momentum() + eta.momentum()).mass2(),
                             (phi[1].momentum() + eta.momentum()).mass2()};
        _h[iloc][1]->fill(sqrt(mPhiEta[0]));
        _h[iloc][1]->fill(sqrt(mPhiEta[1]));
        _dalitz[iloc]->fill(mPhiEta[0], mPhiEta[1]);
        _dalitz[iloc]->fill(mPhiEta[1], mPhiEta[0]);
      }
    }


    /// Normalise histograms etc., after the run
    void finalize() {
      for (unsigned int ix = 0; ix < 3; ++ix) {
        normalize(_dalitz[ix]);
        for (unsigned int iy = 0; iy < 2; ++iy) {
          normalize(_h[ix][iy], 1., false);
        }
      }
    }

    /// @}


    /// @name Histograms
    /// @{
    Histo1DPtr _h[3][2];
    Histo2DPtr _dalitz[3];
    /// @}
  };


  RIVET_DECLARE_PLUGIN(BESIII_2020_I1763897);

}