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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: Beams: e+ e-
Beam energies: ANY
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 
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// -*- 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    , "TMP/nKSKL");
    }


    /// 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();
    }


    /// Normalise histograms etc., after the run
    void finalize() {
      double sigma =  _nKSKL->val()*crossSection()/ sumOfWeights() /picobarn;
      double error =  _nKSKL->err()*crossSection()/ sumOfWeights() /picobarn;
      Scatter2D temphisto(refData(1, 1, 1));
      Scatter2DPtr  mult;
      book(mult, 1, 1, 1);
      for (size_t b = 0; b < temphisto.numPoints(); b++) {
	const double x  = temphisto.point(b).x();
	pair<double,double> ex = temphisto.point(b).xErrs();
	pair<double,double> ex2 = ex;
	if(ex2.first ==0.) ex2. first=0.0001;
	if(ex2.second==0.) ex2.second=0.0001;
	if (inRange(sqrtS()/GeV, x-ex2.first, x+ex2.second)) {
	  mult->addPoint(x, sigma, ex, make_pair(error,error));
	}
	else {
	  mult->addPoint(x, 0., ex, make_pair(0.,.0));
	}
      }
    }

    ///@}


    /// @name Histograms
    ///@{
    CounterPtr _nKSKL;
    ///@}


  };


  RIVET_DECLARE_PLUGIN(BESIII_2021_I1866051);

}