Rivet analyses

title: BESII_2005_I690784

$\chi_{c0}\to \pi^+\pi^- K^+K^-$

Experiment: BESII (BEPC)

Inspire ID: 690784

Status: VALIDATED NOHEPDATA

Authors: - Peter Richardson

References: - Phys.Rev.D 72 (2005) 092002

Beams: * *

Beam energies: ANY

Run details: - Any process producing chi_c0

Measurement of the mass distributions in the decays $\chi_{c0}\to \pi^+\pi^- K^+K^-$. The data were read from the plots in the paper and may not be corrected for backgrounds and efficiency.

Source code:BESII_2005_I690784.cc

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

include "Rivet/Analysis.hh"

include "Rivet/Projections/DecayedParticles.hh"

include "Rivet/Projections/UnstableParticles.hh"

namespace Rivet {

/// @brief chi_c0 -> pi+ pi- K+ K- class BESII_2005_I690784 : public Analysis { public:

/// Constructor
RIVET_DEFAULT_ANALYSIS_CTOR(BESII_2005_I690784);


/// @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 = {{211, 1}, {-211, 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, 4, mode1)) continue;
    const Particle& pim = chi.decayProducts()[ix].at(-211)[0];
    const Particle& pip = chi.decayProducts()[ix].at(211)[0];
    const Particle& Km = chi.decayProducts()[ix].at(-321)[0];
    const Particle& Kp = chi.decayProducts()[ix].at(321)[0];
    _h[0]->fill((Km.momentum() + Kp.momentum()).mass());
    _h[1]->fill((pim.momentum() + pip.momentum()).mass());
    _h[2]->fill((Km.momentum() + pip.momentum()).mass());
    _h[2]->fill((Kp.momentum() + pim.momentum()).mass());
    _h[3]->fill((Km.momentum() + pip.momentum() + pim.momentum()).mass());
    _h[3]->fill((Kp.momentum() + pim.momentum() + pip.momentum()).mass());
  }
}


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

/// @}


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

};

RIVET_DECLARE_PLUGIN(BESII_2005_I690784);

} ```