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BESIII_2019_I1743841

Cross section for $K^+K^-K^+K^-$ and $K^+K^-\phi$ for $E_{\text{CMS}}=2.10$ to $3.08$ GeV
Experiment: BESIII (BEPC)
Inspire ID: 1743841
Status: VALIDATED
Authors:
  • Peter Richardson
References: Beams: e+ e-
Beam energies: ANY
Run details:
  • e+e- to hadrons

Measurement of the cross section for $e^+e^- \to$ $K^+K^-K^+K^-$ and $K^+K^-\phi$ for center of mass energies between 2.10 and 3.08 GeV by the BESIII experiment.

Source code: BESIII_2019_I1743841.cc
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// -*- C++ -*-
#include "Rivet/Analysis.hh"
#include "Rivet/Projections/FinalState.hh"
#include "Rivet/Projections/UnstableParticles.hh"

namespace Rivet {


  /// @brief 2K+2K- and K+K- phi cross section
  class BESIII_2019_I1743841 : public Analysis {
  public:

    /// Constructor
    DEFAULT_RIVET_ANALYSIS_CTOR(BESIII_2019_I1743841);


    /// @name Analysis methods
    //@{

    /// Book histograms and initialise projections before the run
    void init() {
      // Initialise and register projections
      declare(FinalState(), "FS");
      declare(UnstableParticles(), "UFS");
      // book counters
      book(_c2Kp2Km , "TMP/2Kp2Km" );
      book(_cKpKmPhi, "TMP/KpKmPhi");
    }

    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;
      }
      if(ntotal==4 && nCount[321]==2 && nCount[-321]==2)
	_c2Kp2Km->fill();
      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);
	// phi K+K-
	if(ncount==2) {
	  bool matched = true;
	  for(auto const & val : nRes) {
	    if(abs(val.first)==321) {
	      if(val.second!=1) {
		matched = false;
		break;
	      }
	    }
	    else if(val.second!=0) {
	      matched = false;
	      break;
	    }
	  }
	  if(matched)
	    _cKpKmPhi->fill();
	}
      }
    }


    /// Normalise histograms etc., after the run
    void finalize() {
      for(unsigned int ix=1;ix<3;++ix) {
	double sigma = 0., error = 0.;
	if(ix==1) {
	  sigma =  _c2Kp2Km->val();
	  error =  _c2Kp2Km->err();
	}
	else {
	  sigma =  _cKpKmPhi->val();
	  error =  _cKpKmPhi->err();
	}
    	sigma *= crossSection()/ sumOfWeights() /picobarn;
    	error *= crossSection()/ sumOfWeights() /picobarn;
	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 _c2Kp2Km,_cKpKmPhi;
    //@}


  };


  // The hook for the plugin system
  DECLARE_RIVET_PLUGIN(BESIII_2019_I1743841);


}