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SND_2020_I1806118

Cross Section for $e^+e^-\to K^+K^-\pi^0$ and $\phi\pi^0$ from threshold to 2.1 GeV
Experiment: SND (VEPP-2000)
Inspire ID: 1806118
Status: VALIDATED
Authors:
  • Peter Richardson
References: Beams: e+ e-
Beam energies: ANY
Run details:
  • e+ e- to hadrons

Cross section for $e^+e^-\to K^+K^-\pi^0$ between threshold and 2.1 GeV. The $\phi\pi^0$ radiative subprocess is also measured.

Source code: SND_2020_I1806118.cc
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// -*- C++ -*-
#include "Rivet/Analysis.hh"
#include "Rivet/Projections/FinalState.hh"
#include "Rivet/Projections/UnstableParticles.hh"

namespace Rivet {


  /// @brief Add a short analysis description here
  class SND_2020_I1806118 : public Analysis {
  public:

    /// Constructor
    DEFAULT_RIVET_ANALYSIS_CTOR(SND_2020_I1806118);


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

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

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

      // Book histograms
      book( _nKKPi,"TMP/nKKPi" );
      book(_nPhiPi,"TMP/nPhiPi");
    }

    void findChildren(const Particle & p,map<long,int> & nRes, int &ncount) {
      for (const Particle &child : p.children()) {
	if(child.children().empty()) {
	  nRes[child.pid()]-=1;
	  --ncount;
	}
	else
	  findChildren(child,nRes,ncount);
      }
    }

    /// 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;
      }
      // KK pi state
      if(ntotal==3 && nCount[321]==1 &&
	 nCount[-321]==1 && nCount[111]==1)
	_nKKPi->fill();
      // phi pi state
      const FinalState& ufs = apply<FinalState>(event, "UFS");
      for (const Particle& p : ufs.particles(Cuts::pid==333)) {
	if(p.children().empty()) continue;
	map<long,int> nRes = nCount;
	int ncount = ntotal;
	findChildren(p,nRes,ncount);
	if(ncount!=1) continue;
	bool matched = true;
	for(auto const & val : nRes) {
	  if(val.first==111) {
	    if(val.second!=1) {
	      matched = false;
	      break;
	      }
	  }
	  else if(val.second!=0) {
	    matched = false;
	    break;
	  }
	}
	if(matched) {
	  _nPhiPi->fill();
	  break;
	}
      }
    }


    /// Normalise histograms etc., after the run
    void finalize() {
      for(unsigned int ix=1;ix<3;++ix) {
	double sigma,error;
	if(ix==1) {
	  sigma = _nKKPi->val();
	  error = _nKKPi->err();
	}
	else {
	  sigma = _nPhiPi->val();
	  error = _nPhiPi->err();
	}
    	sigma *= crossSection()/ sumOfWeights() /nanobarn;
    	error *= crossSection()/ sumOfWeights() /nanobarn; 
	Scatter2D temphisto(refData(ix, 1, 1));
    	Scatter2DPtr  mult;
        book(mult, ix, 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 _nKKPi,_nPhiPi;
    ///@}


  };


  DECLARE_RIVET_PLUGIN(SND_2020_I1806118);

}