1// -*- C++ -*-
  2#include "Rivet/Analysis.hh"
  3#include "Rivet/Projections/FinalState.hh"
  4#include "Rivet/Projections/FastJets.hh"
  5#include "Rivet/Projections/UnstableParticles.hh"
  6#include "Rivet/Projections/LeptonFinder.hh"
  7#include "Rivet/Projections/MissingMomentum.hh"
  8#include "Rivet/Projections/DirectFinalState.hh"
  9
 10namespace Rivet {
 11
 12
 13  /// @brief e+e- -> phi pi+ pi-
 14  class BESIII_2021_I1997451 : public Analysis {
 15  public:
 16
 17    /// Constructor
 18    RIVET_DEFAULT_ANALYSIS_CTOR(BESIII_2021_I1997451);
 19
 20
 21    /// @name Analysis methods
 22    /// @{
 23
 24    /// Book histograms and initialise projections before the run
 25    void init() {
 26
 27      // Initialise and register projections
 28      declare(FinalState(), "FS");
 29      declare(UnstableParticles(), "UFS");
 30      // counter
 31      book(_cphipippim  , "TMP/phipippim");
 32    }
 33
 34    void findChildren(const Particle & p,map<long,int> & nRes, int &ncount) {
 35      for (const Particle &child : p.children()) {
 36	if(child.children().empty()) {
 37	  nRes[child.pid()]-=1;
 38	  --ncount;
 39	}
 40	else
 41	  findChildren(child,nRes,ncount);
 42      }
 43    }
 44
 45
 46    /// Perform the per-event analysis
 47    void analyze(const Event& event) {
 48      const FinalState& fs = apply<FinalState>(event, "FS");
 49
 50      map<long,int> nCount;
 51      int ntotal(0);
 52      for (const Particle& p : fs.particles()) {
 53        nCount[p.pid()] += 1;
 54        ++ntotal;
 55      }
 56      const FinalState& ufs = apply<FinalState>(event, "UFS");
 57      for (const Particle& p : ufs.particles(Cuts::pid==PID::PHI)) {
 58	if(p.children().empty()) continue;
 59	map<long,int> nRes=nCount;
 60	int ncount = ntotal;
 61	findChildren(p,nRes,ncount);
 62	// phi pi+pi-
 63	if(ncount==2) {
 64	  bool matched = true;
 65	  for(auto const & val : nRes) {
 66	    if(abs(val.first)==211) {
 67	      if(val.second!=1) {
 68		matched = false;
 69		break;
 70	      }
 71	    }
 72	    else if(val.second!=0) {
 73	      matched = false;
 74	      break;
 75	    }
 76	  }
 77	  if(matched) {
 78	    _cphipippim->fill();
 79	    break;
 80	  }
 81	}
 82      }
 83    }
 84
 85
 86    /// Normalise histograms etc., after the run
 87    void finalize() {
 88      double sigma = _cphipippim->val()* crossSection()/ sumOfWeights() /picobarn;
 89      double error = _cphipippim->err()* crossSection()/ sumOfWeights() /picobarn;
 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 _cphipippim;
105    /// @}
106
107
108  };
109
110
111  RIVET_DECLARE_PLUGIN(BESIII_2021_I1997451);
112
113}