Rivet analyses

χc2 decays to K+K−π0, KS0K±π∓ and π+π−π0

Experiment: BESIII (BEPC)

Inspire ID: 1505590

Status: VALIDATED NOHEPDATA

Authors: - Peter Richardson

References: - Phys.Rev.D 96 (2017) 11, 111102

Beams: * *

Beam energies: ANY

Run details: - Any process producing chi_c2

Mass distributions in χc2 decays to K+K−π0, KS0K±π∓ and π+π−π0. The data was read from the plots in the paper and is not corrected for efficiency and acceptance.

Source code:BESIII_2017_I1505590.cc

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

namespace Rivet {


  /// @brief chi_c2 decays
  class BESIII_2017_I1505590 : public Analysis {
  public:

    /// Constructor
    RIVET_DEFAULT_ANALYSIS_CTOR(BESIII_2017_I1505590);


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

    /// Book histograms and initialise projections before the run
    void init() {
      // projections
      UnstableParticles ufs = UnstableParticles(Cuts::pid == 445);
      declare(ufs, "UFS");
      DecayedParticles chi(ufs);
      chi.addStable(PID::PI0);
      chi.addStable(PID::K0S);
      declare(chi, "chi");
      // histograms
      for (unsigned int ix = 0; ix < 4; ++ix) {
        if (ix < 2) book(_h[ix], 1, 1, 1 + ix);
        book(_h[2 + ix], 2, 1, 1 + ix);
      }
    }


    /// Perform the per-event analysis
    void analyze(const Event& event) {
      DecayedParticles chi = apply<DecayedParticles>(event, "chi");
      // loop over particles
      for (unsigned int ix = 0; ix < chi.decaying().size(); ++ix) {
        int sign = 1;
        // K+ K- pi0
        if (chi.modeMatches(ix, 3, mode1)) {
          const Particle& Kp = chi.decayProducts()[ix].at(321)[0];
          const Particle& Km = chi.decayProducts()[ix].at(-321)[0];
          const Particle& pi0 = chi.decayProducts()[ix].at(111)[0];
          _h[0]->fill((Kp.mom() + pi0.mom()).mass() / GeV);
          _h[0]->fill((Km.mom() + pi0.mom()).mass() / GeV);
          _h[1]->fill((Kp.mom() + Km.mom()).mass() / GeV);
          continue;
        }
        // pi+ pi- pi0
        else if (chi.modeMatches(ix, 3, mode3)) {
          const Particle& pip = chi.decayProducts()[ix].at(211)[0];
          const Particle& pim = chi.decayProducts()[ix].at(-211)[0];
          const Particle& pi0 = chi.decayProducts()[ix].at(111)[0];
          _h[5]->fill((pip.mom() + pi0.mom()).mass() / GeV);
          _h[5]->fill((pim.mom() + pi0.mom()).mass() / GeV);
          continue;
        }
        else if (chi.modeMatches(ix, 3, mode2)) {
          sign = 1;
        }
        else if (chi.modeMatches(ix, 3, mode2CC)) {
          sign = -1;
        }
        else {
          continue;
        }
        const Particle& KS0 = chi.decayProducts()[ix].at(310)[0];
        const Particle& Kp = chi.decayProducts()[ix].at(sign * 321)[0];
        const Particle& pim = chi.decayProducts()[ix].at(-sign * 211)[0];
        _h[2]->fill((Kp.mom() + pim.mom()).mass() / GeV);
        _h[3]->fill((KS0.mom() + pim.mom()).mass() / GeV);
        _h[4]->fill((KS0.mom() + Kp.mom()).mass() / GeV);
      }
    }


    /// Normalise histograms etc., after the run
    void finalize() {
      normalize(_h, 1.0, false);
    }

    /// @}


    /// @name Histograms
    /// @{
    Histo1DPtr _h[6];
    const map<PdgId, unsigned int> mode1 = {{321, 1}, {-321, 1}, {111, 1}};
    const map<PdgId, unsigned int> mode2 = {{310, 1}, {321, 1}, {-211, 1}};
    const map<PdgId, unsigned int> mode2CC = {{310, 1}, {-321, 1}, {211, 1}};
    const map<PdgId, unsigned int> mode3 = {{211, 1}, {-211, 1}, {111, 1}};
    /// @}
  };


  RIVET_DECLARE_PLUGIN(BESIII_2017_I1505590);

}