Rivet analyses

title: BESIII_2020_I1763897

$\chi_{c(0,1,2)}\to \phi\phi\eta$

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 $\chi_{c(0,1,2)}\to \phi\phi\eta$. 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++ // -- 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);

} ```