Rivet analyses

title: BESIII_2024_I2860910

Decay of $\chi_{c0}\to p\bar{p} \eta\pi^0$

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 $\chi_{c0}\to p\bar{p} \eta\pi^0$. 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++ // -- 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);

} ```