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 Cross section for $e^+e^-\to \gamma\chi_{c(0,1,2)}$ at energies between 4.009 and 4.36 GeV
 10  class BESIII_2015_I1329785 : public Analysis {
 11  public:
 12
 13    /// Constructor
 14    RIVET_DEFAULT_ANALYSIS_CTOR(BESIII_2015_I1329785);
 15
 16
 17    /// @name Analysis methods
 18    /// @{
 19
 20    /// Book histograms and initialise projections before the run
 21    void init() {
 22      declare(FinalState(), "FS");
 23      declare(UnstableParticles(), "UFS");
 24      book(_nChi0, 1, 1, 8);
 25      book(_nChi1, 2, 1, 8);
 26      book(_nChi2, 3, 1, 8);
 27      for (const string& en : _nChi0.binning().edges<0>()) {
 28        const double end = std::stod(en)*GeV;
 29        if (isCompatibleWithSqrtS(end)) {
 30          _ecms = en;
 31          break;
 32        }
 33      }
 34      if(_ecms.empty()) MSG_ERROR("Beam energy incompatible with analysis.");
 35    }
 36
 37    void findChildren(const Particle & p,map<long,int> & nRes, int &ncount) {
 38      for( const Particle &child : p.children()) {
 39        if(child.children().empty()) {
 40          --nRes[child.pid()];
 41          --ncount;
 42        }
 43        else
 44          findChildren(child,nRes,ncount);
 45      }
 46    }
 47
 48    /// Perform the per-event analysis
 49    void analyze(const Event& event) {
 50      const FinalState& fs = apply<FinalState>(event, "FS");
 51      map<long,int> nCount;
 52      int ntotal(0);
 53      for (const Particle& p :  fs.particles()) {
 54        nCount[p.pid()] += 1;
 55        ++ntotal;
 56      }
 57      const FinalState& ufs = apply<FinalState>(event, "UFS");
 58      for (const Particle& p :  ufs.particles(Cuts::pid==10441 or Cuts::pid==20443 or Cuts::pid==445)) {
 59        if(p.children().empty()) continue;
 60        map<long,int> nRes = nCount;
 61        int ncount = ntotal;
 62        findChildren(p,nRes,ncount);
 63        // chi gamma
 64        if(ncount!=1) continue;
 65        bool matched = true;
 66        for(auto const & val : nRes) {
 67          if(val.first==22) {
 68            if(val.second !=1) {
 69              matched = false;
 70              break;
 71            }
 72          }
 73          else if(val.second!=0) {
 74            matched = false;
 75            break;
 76          }
 77        }
 78        if(matched) {
 79          if(p.pid()==10441)
 80            _nChi0->fill(_ecms);
 81          else if(p.pid()==20443)
 82            _nChi1->fill(_ecms);
 83          else if(p.pid()==445)
 84            _nChi2->fill(_ecms);
 85          break;
 86        }
 87      }
 88    }
 89
 90
 91    /// Normalise histograms etc., after the run
 92    void finalize() {
 93      double fact =  crossSection()/ sumOfWeights() /picobarn;
 94      scale(_nChi0,fact);
 95      scale(_nChi1,fact);
 96      scale(_nChi2,fact);
 97    }
 98    /// @}
 99
100    /// @name Histograms
101    /// @{
102    BinnedHistoPtr<string> _nChi0,_nChi1,_nChi2;
103    string _ecms;
104    /// @}
105
106  };
107
108
109  RIVET_DECLARE_PLUGIN(BESIII_2015_I1329785);
110
111
112}