Rivet analyses

title: BESIII_2017_I1505590

$\chi_{c2}$ decays to $K^+K^-\pi^0$, $K^0_SK^\pm\pi^\mp$ and $\pi^+\pi^-\pi^0$

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 $\chi_{c2}$ decays to $K^+K^-\pi^0$, $K^0_SK^\pm\pi^\mp$ and $\pi^+\pi^-\pi^0$. 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++ // -- 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);

} ```