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BESIII_2019_I1756876

Cross section for $e^+e^-\to D^+D^-\pi^+\pi^-$ for $E_{\text{CMS}}=4.36\to4.60$ GeV
Experiment: BESIII (BEPC)
Inspire ID: 1756876
Status: VALIDATED
Authors:
  • Peter Richardson
References: Beams: e- e+
Beam energies: (2.2, 2.2); (2.2, 2.2); (2.2, 2.2); (2.2, 2.2); (2.3, 2.3); (2.3, 2.3); (2.3, 2.3) GeV
Run details:
  • e+e- to hadrons

Cross section for $e^+e^-\to D^+D^-\pi^+\pi^-$ for $E_{\text{CMS}}=4.36\to4.60$ GeV. The cross sections for the subprocesses $e^+e^-\to D_1(2420)^\pm D^\mp$ and $e^+e^-\to \psi(3770) \pi^+\pi^-$ are measured.

Source code: BESIII_2019_I1756876.cc
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// -*- C++ -*-
#include "Rivet/Analysis.hh"
#include "Rivet/Projections/FinalState.hh"
#include "Rivet/Projections/UnstableParticles.hh"

namespace Rivet {


  /// @brief Cross section for D+D- pi+ pi- (D1 D and psi(3770) pi+pi- subprocesses)
  class BESIII_2019_I1756876 : public Analysis {
  public:

    /// Constructor
    DEFAULT_RIVET_ANALYSIS_CTOR(BESIII_2019_I1756876);


    /// @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(_nD1D, "/TMP/nD1D");
      book(_nPsi, "/TMP/nPsi");

    }

    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) {
      cerr << "testing in analysis\n";
      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");
      bool matched=false;
      for(const Particle& p1 : ufs.particles(Cuts::abspid==411)) {
	int sign = p1.pid()/411;
	map<long,int> nRes = nCount;
	int ncount = ntotal;
	findChildren(p1,nRes,ncount);
	matched=false;
	for(const Particle& p2 : ufs.particles(Cuts::pid==-sign*411)) {
	  map<long,int> nRes2 = nRes;
	  int ncount2 = ncount;
	  findChildren(p2,nRes2,ncount2);
	  if(ncount2!=1) continue;
	  matched=true;
	  for(auto const & val : nRes2) {
	    if(abs(val.first)==211) {
	      if(val.second!=1) {
		matched = false;
		break;
	      }
	    }
	    else if(val.second!=0) {
	      matched = false;
	      break;
	    }
	  }
	  if(matched) break;
	}
	if(matched)
	  break;
      }
      if(!matched) vetoEvent;
      // psi(3770) pi+pi-
      for(const Particle& p1 : ufs.particles(Cuts::abspid==30443)) {
       	if(p1.children().empty()) continue;
	map<long,int> nRes = nCount;
        int ncount = ntotal;
        findChildren(p1,nRes,ncount);
	// psi(3770) pi+pi-
	if(ncount!=2) continue;
	bool matched = true;
	for(auto const & val : nRes) {
	  if(abs(val.first)==211) {
	    if(val.second !=1) {
	      matched = false;
	      break;
	    }
	  }
	  else if(val.second!=0) {
	    matched = false;
	    break;
	  }
	}
	if(matched) {
	  _nPsi->fill();
	  break;
	}
      }
      // D1 D
      for(const Particle& p1 : ufs.particles(Cuts::abspid==10413)) {
       	if(p1.children().empty()) continue;
      	int sign = p1.pid()/10413;
      	map<long,int> nRes = nCount;
      	int ncount = ntotal;
      	findChildren(p1,nRes,ncount);
      	matched=false;
	for(const Particle& p2 : ufs.particles(Cuts::pid==-sign*411)) {
	  map<long,int> nRes2 = nRes;
	  int ncount2 = ncount;
	  findChildren(p2,nRes2,ncount2);
	  if(ncount2!=1) continue;
	  matched=true;
	  for(auto const & val : nRes2) {
	    if(abs(val.first)==211) {
	      if(val.second!=1) {
		matched = false;
		break;
	      }
	    }
	    else if(val.second!=0) {
	      matched = false;
	      break;
	    }
	  }
	  if(matched) break;
	}
	if(matched) {
	  _nD1D->fill();
      	  break;
	}
      }
    }

    /// Normalise histograms etc., after the run
    void finalize() {
      double fact = crossSection()/ sumOfWeights()/picobarn;
      for(unsigned int iy=9;iy<11;++iy) {
	double sigma,error;
	if(iy==9) {
	  sigma = _nD1D->val()*fact;
	  error = _nD1D->err()*fact;
	}
	else if(iy==10) {
	  sigma = _nPsi->val()*fact;
	  error = _nPsi->err()*fact;
	}
	Scatter2D temphisto(refData(1, 1, iy));
        Scatter2DPtr     mult;
	book(mult,1,1,iy);
        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 _nD1D, _nPsi;
    //@}

  };


  // The hook for the plugin system
  DECLARE_RIVET_PLUGIN(BESIII_2019_I1756876);


}