Rivet analyses

title: BESIII_2010_I878544

Mass distributions in $\chi_{cJ}\to 4\pi^0$

Experiment: BESIII (BEPC)

Inspire ID: 878544

Status: VALIDATED NOHEPDATA

Authors: - Peter Richardson

References: - Phys.Rev.D 83 (2011) 012006

Beams: * *

Beam energies: ANY

Run details: - Any process producing chi_c0,1,2

easurement of the mass distributions in the decays $\chi_{cJ}\to 4\pi^0$. The data were read from the plots in the paper and may not be corrected for backgrounds and efficiency.

Source code:BESIII_2010_I878544.cc

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

include "Rivet/Analysis.hh"

include "Rivet/Projections/DecayedParticles.hh"

include "Rivet/Projections/UnstableParticles.hh"

namespace Rivet {

/// @brief chi_cJ -> 4 pi0 class BESIII_2010_I878544 : public Analysis { public:

/// Constructor
RIVET_DEFAULT_ANALYSIS_CTOR(BESIII_2010_I878544);


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

/// Book histograms and initialise projections before the run
void init() {
  // projections
  UnstableParticles ufs = UnstableParticles(Cuts::pid == 10441 || Cuts::pid == 445 || Cuts::pid == 20443);
  declare(ufs, "UFS");
  DecayedParticles chi(ufs);
  chi.addStable(PID::PI0);
  declare(chi, "chi");
  // histograms
  for (unsigned int ix = 0; ix < 3; ++ix) book(_h[ix], 1, 1, 1 + ix);
}


/// Perform the per-event analysis
void analyze(const Event& event) {
  static const map<PdgId, unsigned int>& mode = {{111, 4}};
  DecayedParticles chi = apply<DecayedParticles>(event, "chi");
  // loop over particles
  for (unsigned int ix = 0; ix < chi.decaying().size(); ++ix) {
    if (!chi.modeMatches(ix, 4, mode)) continue;
    const Particles& pi0 = chi.decayProducts()[ix].at(111);
    unsigned int imode = 0;
    if (chi.decaying()[ix].pid() == 20443)
      imode = 1;
    else if (chi.decaying()[ix].pid() == 445)
      imode = 2;
    for (unsigned int ix = 0; ix < pi0.size(); ++ix) {
      for (unsigned int iy = ix + 1; iy < pi0.size(); ++iy) {
        _h[imode]->fill((pi0[ix].momentum() + pi0[iy].momentum()).mass());
      }
    }
  }
}


/// Normalise histograms etc., after the run
void finalize() {
  for (unsigned int ix = 0; ix < 3; ++ix) normalize(_h[ix]);
}

/// @}


/// @name Histograms
/// @{
Histo1DPtr _h[3];
/// @}

};

RIVET_DECLARE_PLUGIN(BESIII_2010_I878544);

} ```