Rivet Analyses Reference

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// -*- C++ -*-
#include "Rivet/Analysis.hh"
#include "Rivet/Projections/FinalState.hh"
#include "Rivet/Projections/UnstableParticles.hh"

namespace Rivet {


  /// @brief e+e- > eta omega and omega pi0
  class BESIII_2022_I2047667 : public Analysis {
  public:

    /// Constructor
    RIVET_DEFAULT_ANALYSIS_CTOR(BESIII_2022_I2047667);


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

    /// Book histograms and initialise projections before the run
    void init() {
      // Initialise and register projections
      declare(FinalState(), "FS");
      declare(UnstableParticles(), "UFS");
      book(_nMeson[0], "/TMP/n_pi0");
      book(_nMeson[1], "/TMP/n_eta");
    }

    void findChildren(const Particle & p,map<long,int> & nRes, int &ncount) {
      for( const Particle &child : p.children()) {
	if(child.children().empty()) {
	  --nRes[child.pid()];
	  --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 UnstableParticles& ufs = apply<UnstableParticles>(event, "UFS");
      for (const Particle& p : ufs.particles(Cuts::pid==223)) {
	if(p.children().empty()) continue;
	map<long,int> nRes = nCount;
	int ncount = ntotal;
	findChildren(p,nRes,ncount);
	if(ncount==1) {
	  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) {
	    _nMeson[0]->fill();
	    continue;
	  }
	}
	else {
	  // check for eta
	  for (const Particle& p2 : ufs.particles(Cuts::pid==221)) {
	    map<long,int> nResB = nRes;
	    int ncountB = ncount;
	    findChildren(p2,nResB,ncountB);
	    if(ncountB!=0) continue;
	    bool matched = true;
	    for(auto const & val : nResB) {
	      if(val.second!=0) {
		matched = false;
		break;
	      }
	    }
	    if(matched) {
	      _nMeson[1]->fill();
	      break;
	    }
	  }
	}
      }
    }


    /// Normalise histograms etc., after the run
    void finalize() {
      double fact = crossSection()/picobarn/sumOfWeights();
      for(unsigned int ix=0;ix<2; ++ix) {
	double sigma = _nMeson[ix]->val()*fact;
	double error = _nMeson[ix]->err()*fact;
	Scatter2D temphisto(refData(1, 1, 1+ix));
	Scatter2DPtr  mult;
	book(mult, 1, 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 _nMeson[2];
    /// @}


  };


  RIVET_DECLARE_PLUGIN(BESIII_2022_I2047667);

}