Rivet analyses

Decay of χc0 → pp̄ηπ0

Experiment: BESIII (BEPC)

Inspire ID: 2860910

Status: VALIDATED NOHEPDATA

Authors: - Peter Richardson

References: - Phys.Rev.D 111 (2025) 3, 032008 - arXiv: 2412.13832

Beams: * *

Beam energies: ANY

Run details: - Any process producing chi_c0

Measurement of the mass distributions in the decays χc0 → pp̄ηπ0. The data were read from the plots in the paper and the background given subtracted but may not be corrected for efficiency.

Source code:BESIII_2024_I2860910.cc

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

namespace Rivet {


  /// @brief chi_c0 -> p pbar eta pi0
  class BESIII_2024_I2860910 : public Analysis {
  public:

    /// Constructor
    RIVET_DEFAULT_ANALYSIS_CTOR(BESIII_2024_I2860910);


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

    /// Book histograms and initialise projections before the run
    void init() {
      UnstableParticles ufs = UnstableParticles(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 ix = 0; ix < 4; ++ix) book(_h[ix], 1, 1, ix + 1);
    }


    /// Perform the per-event analysis
    void analyze(const Event& event) {
      static const map<PdgId, unsigned int>& mode1 = {{2212, 1}, {-2212, 1}, {111, 1}, {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, 4, mode1)) continue;
        const Particle& pi0 = chi.decayProducts()[ix].at(111)[0];
        const Particle& eta = chi.decayProducts()[ix].at(221)[0];
        const Particle& pp = chi.decayProducts()[ix].at(2212)[0];
        const Particle& pb = chi.decayProducts()[ix].at(-2212)[0];
        _h[0]->fill((pp.momentum() + pb.momentum()).mass());
        _h[1]->fill((eta.momentum() + pi0.momentum()).mass());
        _h[2]->fill((pp.momentum() + eta.momentum()).mass());
        _h[2]->fill((pb.momentum() + eta.momentum()).mass());
        _h[3]->fill((pp.momentum() + pi0.momentum()).mass());
        _h[3]->fill((pb.momentum() + pi0.momentum()).mass());
      }
    }


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

    /// @}


    /// @name Histograms
    /// @{
    Histo1DPtr _h[4];
    /// @}
  };


  RIVET_DECLARE_PLUGIN(BESIII_2024_I2860910);

}