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BABAR_2008_I776519

Cross section for $e^+e^-\to D^+D^-$ and $D^0\bar{D}^0$ below 5 GeV
Experiment: BABAR (PEP-II)
Inspire ID: 776519
Status: VALIDATED
Authors:
  • Peter Richardson
References: Beams: e+ e-
Beam energies: ANY
Run details:
  • e+e- to hadrons

Cross section for $e^+e^-\to D^+D^-$ and $D^0\bar{D}^0$ below 5 GeV

Source code: BABAR_2008_I776519.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 BABAR_2008_I776519 : public Analysis {
  public:

    /// Constructor
    DEFAULT_RIVET_ANALYSIS_CTOR(BABAR_2008_I776519);


    /// @name Analysis methods
    //@{

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

      // Initialise and register projections
      declare(FinalState(), "FS");
      declare(UnstableParticles(), "UFS");
      book(_nD0, "/TMP/nD0");
      book(_nDp, "/TMP/nDp");

    }

    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(unsigned int ix=0;ix<ufs.particles().size();++ix) {
	const Particle& p1 = ufs.particles()[ix];
	if(abs(p1.pid())!=411 && abs(p1.pid())!=421)
	  continue;
	map<long,int> nRes = nCount;
	int ncount = ntotal;
	findChildren(p1,nRes,ncount);
	bool matched=false;
	for(unsigned int iy=0;iy<ufs.particles().size();++iy) {
	  if(ix==iy) continue;
	  const Particle& p2 = ufs.particles()[iy];
	  if(p2.pid()!=-p1.pid()) continue;
	  map<long,int> nRes2 = nRes;
	  int ncount2 = ncount;
	  findChildren(p2,nRes2,ncount2);
	  if(ncount2!=0) continue;
	  matched=true;
	  for(auto const & val : nRes2) {
	    if(val.second!=0) {
	      matched = false;
	      break;
	    }
	  }
	  if(matched) break;
	}
	if(matched) {
	  if(abs(p1.pid())==411)
	    _nDp->fill();
	  else if(abs(p1.pid())==421)
	    _nD0->fill();
	}
      }
    }


    /// Normalise histograms etc., after the run
    void finalize() {

      for(unsigned int ix=1;ix<3;++ix) {
	double sigma,error;
	if(ix==1) {
	  sigma = _nD0->val();
	  error = _nD0->err();
	}
	else {
	  sigma = _nDp->val();
	  error = _nDp->err();
	}
    	sigma *= crossSection()/ sumOfWeights() /nanobarn;
    	error *= crossSection()/ sumOfWeights() /nanobarn; 
	Scatter2D temphisto(refData(1, 1, ix));
    	Scatter2DPtr  mult;
        book(mult, 1, 1, ix);
	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 _nD0,_nDp;
    //@}


  };


  // The hook for the plugin system
  DECLARE_RIVET_PLUGIN(BABAR_2008_I776519);


}