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- > sigma+- sigmabar -+
 10  class BESIII_2020_I1814783 : public Analysis {
 11  public:
 12
 13    /// Constructor
 14    RIVET_DEFAULT_ANALYSIS_CTOR(BESIII_2020_I1814783);
 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      for(unsigned int ix=0;ix<2;++ix) {
 26        book(_n_plus [ix],1+ix,1,1);
 27        book(_n_minus[ix],1+ix,1,2);
 28        for (const string& en : _n_plus[ix].binning().edges<0>()) {
 29          const double end = std::stod(en)*GeV;
 30          if (isCompatibleWithSqrtS(end)) {
 31            _ecms[ix] = en;
 32            break;
 33          }
 34        }
 35      }
 36      if(isCompatibleWithSqrtS(2.396*GeV)) {
 37        book(_h_cTheta_A,3,1,1);
 38        book(_h_cTheta_B,3,1,2);
 39      }
 40      if (_ecms[0].empty() && _ecms[1].empty()) {
 41        MSG_ERROR("Beam energy incompatible with analysis.");
 42      }
 43    }
 44
 45    void findChildren(const Particle & p,map<long,int> & nRes, int &ncount) {
 46      for(const Particle &child : p.children()) {
 47        if(child.children().empty()) {
 48          nRes[child.pid()]-=1;
 49          --ncount;
 50        }
 51        else
 52          findChildren(child,nRes,ncount);
 53      }
 54    }
 55
 56    /// Perform the per-event analysis
 57    void analyze(const Event& event) {
 58      const FinalState& fs = apply<FinalState>(event, "FS");
 59      // total hadronic and muonic cross sections
 60      map<long,int> nCount;
 61      int ntotal(0);
 62      for (const Particle& p : fs.particles()) {
 63        nCount[p.pid()] += 1;
 64        ++ntotal;
 65      }
 66      // find the Sigmas
 67      const FinalState& ufs = apply<UnstableParticles>(event, "UFS");
 68      for(unsigned int ix=0;ix<ufs.particles().size();++ix) {
 69        const Particle& p1 = ufs.particles()[ix];
 70        if(abs(p1.pid())!=3112&&abs(p1.pid())!=3222) continue;
 71        bool matched = false;
 72        // check fs
 73        bool fs = true;
 74        for(const Particle & child : p1.children()) {
 75          if(child.pid()==p1.pid()) {
 76            fs = false;
 77            break;
 78          }
 79        }
 80        if(!fs) continue;
 81        // find the children
 82        map<long,int> nRes = nCount;
 83        int ncount = ntotal;
 84        findChildren(p1,nRes,ncount);
 85        for(unsigned int iy=ix+1;iy<ufs.particles().size();++iy) {
 86          const Particle& p2 = ufs.particles()[iy];
 87          if(p2.pid() != -p1.pid()) continue;
 88          // check fs
 89          bool fs = true;
 90          for(const Particle & child : p2.children()) {
 91            if(child.pid()==p2.pid()) {
 92              fs = false;
 93              break;
 94            }
 95          }
 96          if(!fs) continue;
 97          map<long,int> nRes2 = nRes;
 98          int ncount2 = ncount;
 99          findChildren(p2,nRes2,ncount2);
100          if(ncount2!=0) continue;
101          matched=true;
102          for(auto const & val : nRes2) {
103            if(val.second!=0) {
104              matched = false;
105              break;
106            }
107          }
108          if(matched) {
109            if(abs(p1.pid())==3222) {
110              for(unsigned int ix=0;ix<2;++ix) {
111                if(!_ecms[ix].empty()) _n_plus[ix]->fill(_ecms[ix]);
112              }
113              if(_h_cTheta_A) {
114                double cTheta = p1.pid()>0 ?
115                  cos(p1.momentum().polarAngle()) :
116                  cos(p2.momentum().polarAngle());
117                _h_cTheta_A->fill(cTheta);
118                _h_cTheta_B->fill(cTheta);
119              }
120            }
121            else if(abs(p1.pid())==3112) {
122              for(unsigned int ix=0;ix<2;++ix) {
123                if(!_ecms[ix].empty()) _n_minus[ix]->fill(_ecms[ix]);
124              }
125            }
126            break;
127          }
128        }
129        if(matched) break;
130      }
131    }
132
133
134    /// Normalise histograms etc., after the run
135    void finalize() {
136      if(_h_cTheta_A) {
137        normalize(_h_cTheta_A);
138        normalize(_h_cTheta_B);
139      }
140      double fact = crossSection()/ sumOfWeights() /picobarn;
141      for(unsigned int iy=0;iy<2;++iy) {
142        scale(_n_plus [iy],fact);
143        scale(_n_minus[iy],fact);
144      }
145    }
146    /// @}
147
148
149    /// @name Histograms
150    /// @{
151    BinnedHistoPtr<string> _n_plus[2],_n_minus[2];
152    Histo1DPtr _h_cTheta_A,_h_cTheta_B;
153    string _ecms[2];
154    /// @}
155
156  };
157
158
159  RIVET_DECLARE_PLUGIN(BESIII_2020_I1814783);
160
161}