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CMD3_2019_I1770428

$e^+e^-\to K^0_SK^0_S\pi^+\pi^-$ below 2 GeV
Experiment: CMD3 (VEPP-2M)
Inspire ID: 1770428
Status: VALIDATED
Authors:
  • Peter Richardson
References: Beams: e- e+
Beam energies: ANY
Run details:
  • e+e- to hadrons

Measurement of the cross section for $e^+e^-\to K^0_SK^0_S\pi^+\pi^-$ below 2 GeV by the CMD3 experiment

Source code: CMD3_2019_I1770428.cc
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// -*- C++ -*-
#include "Rivet/Analysis.hh"
#include "Rivet/Projections/FinalState.hh"

namespace Rivet {


  /// @brief CMD3 K0 K0 pi+pi-
  class CMD3_2019_I1770428 : public Analysis {
  public:

    /// Constructor
    DEFAULT_RIVET_ANALYSIS_CTOR(CMD3_2019_I1770428);


    /// @name Analysis methods
    //@{

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

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

      // Book histograms
      book(_cK0K0pippim , "TMP/K0K0pippim");
      book( _h_pipi ,2,1,1);
      book( _h_total,2,1,2);
    }


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

      map<long,int> nCount;
      int ntotal(0);
      Particles pip,k0;
      for (const Particle& p : fs.particles()) {
	nCount[p.pid()] += 1;
	if(p.abspid()==211)
	  pip.push_back(p);
	else if(p.pid()==310)
	  k0.push_back(p);
	++ntotal;
      }
      if(ntotal==4 && nCount[310]==2 && nCount[211]==1 && nCount[-211]==1) {
	_cK0K0pippim->fill();
	FourMomentum ppipi = pip[0].momentum()+pip[1].momentum();
	_h_pipi->fill(ppipi.mass()/MeV);
	for(unsigned int ix=0;ix<2;++ix)
	  _h_total->fill((ppipi+k0[ix].momentum()).mass()/MeV);
      }
    }


    /// Normalise histograms etc., after the run
    void finalize() {
      normalize(_h_pipi );
      normalize(_h_total);
      double fact = crossSection()/ sumOfWeights() /nanobarn;
      double sigma = _cK0K0pippim->val()*fact;
      double error = _cK0K0pippim->err()*fact;
      Scatter2D temphisto(refData(1, 1, 6));
      Scatter2DPtr  mult;
      book(mult, 1, 1, 6);
      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()/MeV, 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 _cK0K0pippim;
    Histo1DPtr _h_pipi, _h_total;
    //@}


  };


  // The hook for the plugin system
  DECLARE_RIVET_PLUGIN(CMD3_2019_I1770428);


}