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BESIII_2020_I1788734

Cross section for $e^+e^-\to \phi\eta^\prime$ for $\sqrt{s}$ between 3.05 and 3.08 GeV
Experiment: BESIII (BEPC)
Inspire ID: 1788734
Status: VALIDATED
Authors:
  • Peter Richardson
References: Beams: e+ e-
Beam energies: ANY
    No run details listed

Measurement of the cross section for $e^+e^-\to \phi\eta^\prime$ for $\sqrt{s}$ between 3.05 and 3.08 GeV by BESIII

Source code: BESIII_2020_I1788734.cc
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// -*- C++ -*-
#include "Rivet/Analysis.hh"
#include "Rivet/Projections/FinalState.hh"
#include "Rivet/Projections/UnstableParticles.hh"

namespace Rivet {


  /// @brief e+e- > phi eta'
  class BESIII_2020_I1788734 : public Analysis {
  public:

    /// Constructor
    DEFAULT_RIVET_ANALYSIS_CTOR(BESIII_2020_I1788734);


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

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

      // Initialise and register projections
      declare(FinalState(), "FS");
      declare(UnstableParticles(), "UFS");
      book(_nEtaPhi, "TMP/phietaprime");
    }

    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;
      }
      const FinalState& ufs = apply<FinalState>(event, "UFS");
      for (const Particle& p : ufs.particles(Cuts::pid==PID::PHI)) {
	if(p.children().empty()) continue;
	map<long,int> nRes=nCount;
	int ncount = ntotal;
	findChildren(p,nRes,ncount);
	for (const Particle& p2 : ufs.particles(Cuts::pid==PID::ETAPRIME)) {
	  if(p2.parents()[0].isSame(p)) continue;
	  map<long,int> nResB = nRes;
	  int ncountB = ncount;
	  findChildren(p2,nResB,ncountB);
	  if(ncountB!=0) continue;
	  bool matched2 = true;
	  for(auto const & val : nResB) {
	    if(val.second!=0) {
	      matched2 = false;
	      break;
	    }
	  }
	  if(matched2) {
	    _nEtaPhi->fill();
	  }
	}
      }
    }


    /// Normalise histograms etc., after the run
    void finalize() {
      double sigma = _nEtaPhi->val()*crossSection()/ sumOfWeights() /picobarn;
      double error = _nEtaPhi->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 _nEtaPhi;
    ///@}


  };


  DECLARE_RIVET_PLUGIN(BESIII_2020_I1788734);

}