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- > eta(') gamma
 10  class BABAR_2006_I716277 : public Analysis {
 11  public:
 12
 13    /// Constructor
 14    RIVET_DEFAULT_ANALYSIS_CTOR(BABAR_2006_I716277);
 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(_numEtaGamma,      1, 1, 1);
 26      book(_numEtaPrimeGamma, 1, 1, 2);
 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()];
 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
 43      const FinalState& fs = apply<FinalState>(event, "FS");
 44
 45      map<long,int> nCount;
 46      int ntotal(0);
 47      for (const Particle& p : fs.particles()) {
 48	nCount[p.pid()] += 1;
 49	++ntotal;
 50      }
 51
 52      const FinalState& ufs = apply<FinalState>(event, "UFS");
 53      for (const Particle& p : ufs.particles()) {
 54	if(p.children().empty()) continue;
 55	// find the eta/eta prime
 56        if(p.pid()!=221 && p.pid()!=331) continue;
 57	map<long,int> nRes = nCount;
 58	int ncount = ntotal;
 59	findChildren(p,nRes,ncount);
 60	// eta pi+pi-
 61	if(ncount!=1) continue;
 62	bool matched = true;
 63	for(auto const & val : nRes) {
 64	  if(val.first==22) {
 65	    if(val.second !=1) {
 66	      matched = false;
 67	      break;
 68	    }
 69	  }
 70	  else if(val.second!=0) {
 71	    matched = false;
 72	    break;
 73	  }
 74	}
 75	if(matched) {
 76	  if(p.pid()==221)
 77	    _numEtaGamma->fill("10.58"s);
 78	  else
 79	    _numEtaPrimeGamma->fill("10.58"s);
 80	}
 81      }
 82    }
 83
 84    /// Normalise histograms etc., after the run
 85    void finalize() {
 86      double fact = crossSection()/ sumOfWeights() /femtobarn;
 87      scale(_numEtaGamma,fact);
 88      scale(_numEtaPrimeGamma,fact);
 89    }
 90
 91    /// @}
 92
 93
 94    /// @name Histograms
 95    /// @{
 96    BinnedHistoPtr<string> _numEtaGamma,_numEtaPrimeGamma;
 97    /// @}
 98
 99
100  };
101
102
103  RIVET_DECLARE_PLUGIN(BABAR_2006_I716277);
104
105
106}