Rivet analyses

title: BESIII_2018_I1691798

Cross-section for $K^0_SK^\pm\pi^\mp$ between 3.8 and 4.6 GeV

Experiment: BESIII (BEPC II)

Inspire ID: 1691798

Status: VALIDATED

Authors: - Peter Richardson

References: - arXiv: 1808.08733

Beams: e+ e-

Beam energies: (1.9, 1.9); (1.9, 1.9); (2.0, 2.0); (2.0, 2.0); (2.1, 2.1); (2.1, 2.1); (2.1, 2.1); (2.1, 2.1); (2.1, 2.1); (2.1, 2.1); (2.2, 2.2); (2.2, 2.2); (2.2, 2.2); (2.2, 2.2); (2.3, 2.3)GeV

Run details: - e+e- to hadrons

Measurement of the cross section for $K^0_SK^\pm\pi^\mp$ between 3.8 and 4.6 GeV.

Source code:BESIII_2018_I1691798.cc

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

include "Rivet/Analysis.hh"

include "Rivet/Projections/FinalState.hh"

namespace Rivet {

/// @brief Cross-section for KSO K+-pi-+ between 3.8 and 4.6 GeV class BESIII_2018_I1691798 : public Analysis { public:

/// Constructor
RIVET_DEFAULT_ANALYSIS_CTOR(BESIII_2018_I1691798);


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

/// Book histograms and initialise projections before the run
void init() {
  // Initialise and register projections
  declare(FinalState(), "FS");
  book(_nKKpi, 1, 1, 1);

  for (const string& en : _nKKpi.binning().edges<0>()) {
    const double eval = stod(en) * GeV;
    if (isCompatibleWithSqrtS(eval)) {
      _sqs = en;
      break;
    }
  }
  raiseBeamErrorIf(_sqs.empty());
}


/// Perform the per-event analysis
void analyze(const Event& event) {
  const FinalState& fs = apply<FinalState>(event, "FS");

  map<long, int> nCount;
  int ntotal(0);
  for (const Particle& p : fs.particles()) {
    nCount[p.pid()] += 1;
    ++ntotal;
  }

  if (ntotal == 3 && nCount[310] == 1
      && ((nCount[321] = 1 && nCount[-211] == 1) || (nCount[-321] = 1 && nCount[211] == 1)))
    _nKKpi->fill(_sqs);
}


/// Normalise histograms etc., after the run
void finalize() {
  scale(_nKKpi, crossSection() / sumOfWeights() / picobarn);
}

/// @}


/// @name Histograms
/// @{
BinnedHistoPtr<string> _nKKpi;
string _sqs = "";
/// @}

};

RIVET_DECLARE_PLUGIN(BESIII_2018_I1691798);

} ```