1// -*- C++ -*-
  2#include "Rivet/Analysis.hh"
  3#include "Rivet/Projections/UnstableParticles.hh"
  4#include "Rivet/Projections/FinalState.hh"
  5
  6namespace Rivet {
  7
  8
  9  /// @brief e+e- -> phi lambda lambda bar
 10  class BESIII_2021_I1859248 : public Analysis {
 11  public:
 12
 13    /// Constructor
 14    RIVET_DEFAULT_ANALYSIS_CTOR(BESIII_2021_I1859248);
 15
 16
 17    /// @name Analysis methods
 18    ///@{
 19
 20    /// Book histograms and initialise projections before the run
 21    void init() {
 22
 23      // Initialise and register projections
 24      declare(FinalState(), "FS");
 25      declare(UnstableParticles(), "UFS");
 26      // counter
 27      book(_c_phiLL, "TMP/c_phiLL");
 28    }
 29
 30    void findChildren(const Particle & p,map<long,int> & nRes, int &ncount) {
 31      for(const Particle &child : p.children()) {
 32	if(child.children().empty()) {
 33	  nRes[child.pid()]-=1;
 34	  --ncount;
 35	}
 36	else
 37	  findChildren(child,nRes,ncount);
 38      }
 39    }
 40
 41    /// Perform the per-event analysis
 42    void analyze(const Event& event) {
 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      const FinalState& ufs = apply<FinalState>(event, "UFS");
 52      // loop over phi mesons
 53      for (const Particle& phi : ufs.particles(Cuts::pid==333)) {
 54	bool matched = false;
 55	map<long,int> nRes=nCount;
 56	int ncount = ntotal;
 57	findChildren(phi,nRes,ncount);
 58	// then Lambda baryons
 59	for (const Particle& lambda : ufs.particles(Cuts::pid==3122)) {
 60	  map<long,int> nResB = nRes;
 61	  int ncountB = ncount;
 62	  findChildren(lambda,nResB,ncountB);
 63	  for (const Particle& lambar : ufs.particles(Cuts::pid==-3122)) {
 64	    map<long,int> nResC = nResB;
 65	    int ncountC = ncountB;
 66	    findChildren(lambar,nResC,ncountC);
 67	    for(auto const & val : nResC) {
 68	      if(val.second!=0) {
 69		matched = false;
 70		break;
 71	      }
 72	    }
 73	    if(matched) {
 74	      _c_phiLL->fill();
 75	      break;
 76	    }
 77	  }
 78	  if(matched) break;
 79	}
 80	if(matched) break;
 81      }
 82    }
 83
 84
 85    /// Normalise histograms etc., after the run
 86    void finalize() {
 87      double fact = crossSection()/ sumOfWeights() /picobarn;
 88      double sigma = _c_phiLL->val()*fact;
 89      double error = _c_phiLL->err()*fact;
 90      Estimate1DPtr  mult;
 91      book(mult, 1, 1, 1);
 92      for (auto& b : mult->bins()) {
 93        if (inRange(sqrtS()/GeV, b.xMin(), b.xMax())) {
 94          b.set(sigma, error);
 95        }
 96      }
 97    }
 98
 99    ///@}
100
101
102    /// @name Histograms
103    ///@{
104    CounterPtr _c_phiLL;
105    ///@}
106
107
108  };
109
110
111  RIVET_DECLARE_PLUGIN(BESIII_2021_I1859248);
112
113}