1// -*- C++ -*-
  2#include "Rivet/Analysis.hh"
  3#include "Rivet/Projections/FinalState.hh"
  4#include "Rivet/Projections/UnstableParticles.hh"
  5
  6namespace Rivet {
  7
  8
  9  /// @brief  e+e- -> p pbar eta/omega
 10  class BESIII_2021_I1845443 : public Analysis {
 11  public:
 12
 13    /// Constructor
 14    RIVET_DEFAULT_ANALYSIS_CTOR(BESIII_2021_I1845443);
 15
 16
 17    /// @name Analysis methods
 18    ///@{
 19
 20    /// Book histograms and initialise projections before the run
 21    void init() {
 22      // Initialise and register projections
 23      declare(FinalState(), "FS");
 24      declare(UnstableParticles(), "UFS");
 25      book(_nEta, "/TMP/nEta" );
 26      book(_nOmega, "/TMP/nOmega" );
 27    }
 28
 29    void findChildren(const Particle & p,map<long,int> & nRes, int &ncount) {
 30      for (const Particle &child : p.children()) {
 31	if(child.children().empty()) {
 32	  nRes[child.pid()]-=1;
 33	  --ncount;
 34	}
 35	else
 36	  findChildren(child,nRes,ncount);
 37      }
 38    }
 39
 40    /// Perform the per-event analysis
 41    void analyze(const Event& event) {
 42      const FinalState& fs = apply<FinalState>(event, "FS");
 43      // total hadronic and muonic cross sections
 44      map<long,int> nCount;
 45      int ntotal(0);
 46      for (const Particle& p : fs.particles()) {
 47	nCount[p.pid()] += 1;
 48	++ntotal;
 49      }
 50      // find the eta/omega
 51      const FinalState& ufs = apply<UnstableParticles>(event, "UFS");
 52      for(const Particle& p : ufs.particles(Cuts::pid==PID::ETA or Cuts::pid==PID::OMEGA)) {
 53	map<long,int> nRes = nCount;
 54	int ncount = ntotal;
 55	findChildren(p,nRes,ncount);
 56	bool matched=true;
 57	for(auto const & val : nRes) {
 58	  if(abs(val.first)==PID::PROTON) {
 59	    if(val.second!=1) {
 60	      matched = false;
 61	      break;
 62	    }
 63	  }
 64	  else if(val.second!=0) {
 65	    matched = false;
 66	    break;
 67	  }
 68	}
 69	if(matched) {
 70	  if(p.pid()==PID::ETA)
 71	    _nEta->fill();
 72	  else
 73	    _nOmega->fill();
 74	  break;
 75	}
 76      }
 77    }
 78
 79
 80    /// Normalise histograms etc., after the run
 81    void finalize() {
 82      for(unsigned int ix=1;ix<3;++ix) {
 83        double sigma,error;
 84        if(ix==1) {
 85          sigma = _nEta->val();
 86          error = _nEta->err();
 87        }
 88        else {
 89          sigma = _nOmega->val();
 90          error = _nOmega->err();
 91        }
 92        sigma *= crossSection()/ sumOfWeights() /picobarn;
 93        error *= crossSection()/ sumOfWeights() /picobarn;
 94        Estimate1DPtr  mult;
 95        book(mult, ix, 1, 1);
 96        for (auto& b : mult->bins()) {
 97          if (inRange(sqrtS()/GeV, b.xMin(), b.xMax())) {
 98            b.set(sigma, error);
 99          }
100        }
101      }
102    }
103
104    ///@}
105
106
107    /// @name Histograms
108    ///@{
109    CounterPtr _nEta,_nOmega;
110    ///@}
111
112
113  };
114
115
116  RIVET_DECLARE_PLUGIN(BESIII_2021_I1845443);
117
118}