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, "TMP/chi0");
 25      book(_nChi1, "TMP/chi1");
 26      book(_nChi2, "TMP/chi2");
 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      const FinalState& fs = apply<FinalState>(event, "FS");
 43      map<long,int> nCount;
 44      int ntotal(0);
 45      for (const Particle& p :  fs.particles()) {
 46        nCount[p.pid()] += 1;
 47        ++ntotal;
 48      }
 49      const FinalState& ufs = apply<FinalState>(event, "UFS");
 50      for (const Particle& p :  ufs.particles(Cuts::pid==10441 or Cuts::pid==20443 or Cuts::pid==445)) {
 51        if(p.children().empty()) continue;
 52        map<long,int> nRes = nCount;
 53        int ncount = ntotal;
 54        findChildren(p,nRes,ncount);
 55        // chi gamma
 56        if(ncount!=1) continue;
 57        bool matched = true;
 58        for(auto const & val : nRes) {
 59          if(val.first==22) {
 60            if(val.second !=1) {
 61              matched = false;
 62              break;
 63            }
 64          }
 65          else if(val.second!=0) {
 66            matched = false;
 67            break;
 68          }
 69        }
 70        if(matched) {
 71          if(p.pid()==10441)
 72            _nChi0->fill();
 73          else if(p.pid()==20443)
 74            _nChi1->fill();
 75          else if(p.pid()==445)
 76            _nChi2->fill();
 77          break;
 78        }
 79      }
 80    }
 81
 82
 83    /// Normalise histograms etc., after the run
 84    void finalize() {
 85
 86      double fact =  crossSection()/ sumOfWeights() /picobarn;
 87      for(unsigned int ix=1;ix<4;++ix) {
 88        double sigma(0.),error(0.);
 89        if(ix==1) {
 90          sigma = _nChi0->val()*fact;
 91          error = _nChi0->err()*fact;
 92        }
 93        else if(ix==2) {
 94          sigma = _nChi1->val()*fact;
 95          error = _nChi1->err()*fact;
 96        }
 97        else if(ix==3) {
 98          sigma = _nChi2->val()*fact;
 99          error = _nChi2->err()*fact;
100        }
101        Estimate1DPtr  mult;
102        book(mult,ix, 1, 8);
103        for (auto& b : mult->bins()) {
104          if (inRange(sqrtS()/GeV, b.xMin(), b.xMax())) {
105            b.set(sigma, error);
106          }
107        }
108      }
109    }
110    /// @}
111
112    /// @name Histograms
113    /// @{
114    CounterPtr _nChi0,_nChi1,_nChi2;
115    /// @}
116
117  };
118
119
120  RIVET_DECLARE_PLUGIN(BESIII_2015_I1329785);
121
122
123}