Rivet analyses

title: BESIII_2014_I1280710

$\chi_{c(1,2)}\to \eta^\prime K^+K^-$

Experiment: BESIII ()

Inspire ID: 1280710

Status: VALIDATED NOHEPDATA

Authors: - Peter Richardson

References: - Phys.Rev.D 89 (2014) 7, 074030

Beams: * *

Beam energies: ANY

Run details: - Any process producing chi_c1 or chi_c2

Measurement of the mass distributions in the decays $\chi_{c(1,2)}\to \eta^\prime K^+K^-$. The data were read from the plots in the paper and may not be corrected for efficiency.

Source code:BESIII_2014_I1280710.cc

```c++ // -- C++ --

include "Rivet/Analysis.hh"

include "Rivet/Projections/DecayedParticles.hh"

include "Rivet/Projections/UnstableParticles.hh"

namespace Rivet {

/// @brief chi_c -> eta' K+K- class BESIII_2014_I1280710 : public Analysis { public:

/// Constructor
RIVET_DEFAULT_ANALYSIS_CTOR(BESIII_2014_I1280710);


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

/// Book histograms and initialise projections before the run
void init() {
  UnstableParticles ufs = UnstableParticles(Cuts::pid == 20443 or Cuts::pid == 445);
  declare(ufs, "UFS");
  DecayedParticles chi(ufs);
  chi.addStable(PID::PI0);
  chi.addStable(PID::K0S);
  chi.addStable(PID::ETA);
  chi.addStable(PID::ETAPRIME);
  declare(chi, "chi");
  for (unsigned int ix = 0; ix < 4; ++ix)
    for (unsigned int iy = 0; iy < 2; ++iy) book(_h[ix][iy], 1 + ix, 1, 1 + iy);
  for (unsigned int ix = 0; ix < 2; ++ix)
    book(_dalitz[ix], "dalitz_" + toString(ix + 1), 50, 2., 10., 50, 2., 10.);
}


/// Perform the per-event analysis
void analyze(const Event& event) {
  static const map<PdgId, unsigned int>& mode1 = {{331, 1}, {321, 1}, {-321, 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, mode1)) continue;
    unsigned int iloc = chi.decaying()[ix].pid() == 445 ? 1 : 0;
    const Particle& eta = chi.decayProducts()[ix].at(331)[0];
    const Particle& Km = chi.decayProducts()[ix].at(-321)[0];
    const Particle& Kp = chi.decayProducts()[ix].at(321)[0];
    double m1 = (Kp.momentum() + Km.momentum()).mass2();
    double m2 = (eta.momentum() + Kp.momentum()).mass2();
    double m3 = (eta.momentum() + Km.momentum()).mass2();
    _dalitz[iloc]->fill(m2, m3);
    for (unsigned int ix = 0; ix < 2; ++ix) {
      _h[2 * iloc + ix][0]->fill(sqrt(m1));
      _h[2 * iloc + ix][1]->fill(sqrt(m2));
      _h[2 * iloc + ix][1]->fill(sqrt(m3));
    }
  }
}


/// Normalise histograms etc., after the run
void finalize() {
  for (unsigned int iy = 0; iy < 2; ++iy) {
    normalize(_dalitz[iy]);
    for (unsigned int ix = 0; ix < 4; ++ix) normalize(_h[ix][iy], 1., false);
  }
}

/// @}


/// @name Histograms
/// @{
Histo1DPtr _h[4][2];
Histo2DPtr _dalitz[2];
/// @}

};

RIVET_DECLARE_PLUGIN(BESIII_2014_I1280710);

} ```