Rivet analyses

title: BESIII_2021_I1866051

Cross section for $e^+e^-\to$ $K_S^0K_L^0$between2.00 and 3.08 GeV

Experiment: BESIII (BEPC)

Inspire ID: 1866051

Status: VALIDATED

Authors: - Peter Richardson

References: - arXiv: 2105.13597

Beams: e+ e-

Beam energies: (1.0, 1.0); (1.0, 1.0); (1.1, 1.1); (1.1, 1.1); (1.1, 1.1); (1.1, 1.1); (1.1, 1.1); (1.1, 1.1); (1.2, 1.2); (1.2, 1.2); (1.2, 1.2); (1.3, 1.3); (1.3, 1.3); (1.4, 1.4); (1.5, 1.5)GeV

Run details: - e+e- to hadrons

Measurement of the cross section for $e^+e^-\to$ $K_S^0K_L^0$ for energies between 2.00 and 3.08 GeV.

Source code:BESIII_2021_I1866051.cc

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

include "Rivet/Analysis.hh"

include "Rivet/Projections/FinalState.hh"

namespace Rivet {

/// @brief e+e- > K0K0 class BESIII_2021_I1866051 : public Analysis { public:

/// Constructor
RIVET_DEFAULT_ANALYSIS_CTOR(BESIII_2021_I1866051);


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

/// Book histograms and initialise projections before the run
void init() {

  // Initialise and register projections
  declare(FinalState(), "FS");

  // Book histograms
  book(_nKSKL, 1, 1, 1);
  for (const string& en : _nKSKL.binning().edges<0>()) {
    const double end = stod(en) * GeV;
    if (isCompatibleWithSqrtS(end)) {
      _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 == 2 && nCount[130] == 1 && nCount[310] == 1) {
    _nKSKL->fill(_sqs);
  }
}


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

///@}


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

};

RIVET_DECLARE_PLUGIN(BESIII_2021_I1866051);

} ```