Rivet analyses

Mass distributions in χcJ → 4π0

Experiment: BESIII (BEPC)

Inspire ID: 878544

Status: VALIDATED NOHEPDATA

Authors: - Peter Richardson

References: - Phys.Rev.D 83 (2011) 012006

Beams: * *

Beam energies: ANY

Run details: - Any process producing chi_c0,1,2

easurement of the mass distributions in the decays χcJ → 4π0. The data were read from the plots in the paper and may not be corrected for backgrounds and efficiency.

Source code:BESIII_2010_I878544.cc

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

namespace Rivet {


  /// @brief chi_cJ -> 4 pi0
  class BESIII_2010_I878544 : public Analysis {
  public:

    /// Constructor
    RIVET_DEFAULT_ANALYSIS_CTOR(BESIII_2010_I878544);


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

    /// Book histograms and initialise projections before the run
    void init() {
      // projections
      UnstableParticles ufs = UnstableParticles(Cuts::pid == 10441 || Cuts::pid == 445 || Cuts::pid == 20443);
      declare(ufs, "UFS");
      DecayedParticles chi(ufs);
      chi.addStable(PID::PI0);
      declare(chi, "chi");
      // histograms
      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) {
      static const map<PdgId, unsigned int>& mode = {{111, 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& pi0 = chi.decayProducts()[ix].at(111);
        unsigned int imode = 0;
        if (chi.decaying()[ix].pid() == 20443)
          imode = 1;
        else if (chi.decaying()[ix].pid() == 445)
          imode = 2;
        for (unsigned int ix = 0; ix < pi0.size(); ++ix) {
          for (unsigned int iy = ix + 1; iy < pi0.size(); ++iy) {
            _h[imode]->fill((pi0[ix].momentum() + pi0[iy].momentum()).mass());
          }
        }
      }
    }


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

    /// @}


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


  RIVET_DECLARE_PLUGIN(BESIII_2010_I878544);

}