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- -> eta J/psi
 10  class BESIII_2012_I1126960 : public Analysis {
 11  public:
 12
 13    /// Constructor
 14    RIVET_DEFAULT_ANALYSIS_CTOR(BESIII_2012_I1126960);
 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(_h,1,1,1);
 25    }
 26
 27    void findChildren(const Particle & p,map<long,int> & nRes, int &ncount) {
 28      for (const Particle &child : p.children()) {
 29        if (child.children().empty()) {
 30          --nRes[child.pid()];
 31          --ncount;
 32        }
 33        else {
 34          findChildren(child,nRes,ncount);
 35        }
 36      }
 37    }
 38
 39    /// Perform the per-event analysis
 40    void analyze(const Event& event) {
 41      const FinalState& fs = apply<FinalState>(event, "FS");
 42      map<long,int> nCount;
 43      int ntotal(0);
 44      for (const Particle& p : fs.particles()) {
 45        nCount[p.pid()] += 1;
 46        ++ntotal;
 47      }
 48      const FinalState& ufs = apply<FinalState>(event, "UFS");
 49      for (const Particle& p : ufs.particles(Cuts::pid==PID::JPSI)) {
 50        if (p.children().empty()) continue;
 51        // find the J/psi
 52        map<long,int> nRes = nCount;
 53        int ncount = ntotal;
 54        findChildren(p,nRes,ncount);
 55        bool matched=false;
 56        for (const Particle& p2 : ufs.particles(Cuts::pid==PID::ETA)) {
 57          if (p2.children().empty()) continue;
 58          bool JpsiParent=false;
 59          Particle parent=p2;
 60          while (!parent.parents().empty()) {
 61            parent=parent.parents()[0];
 62            if (parent.pid()==PID::JPSI) {
 63              JpsiParent=true;
 64              break;
 65            }
 66          }
 67          if (JpsiParent) continue;
 68          map<long,int> nRes2 = nRes;
 69          int ncount2 = ncount;
 70          findChildren(p2,nRes2,ncount2);
 71          if (ncount2!=0) continue;
 72          matched = true;
 73          for (const auto& val : nRes2) {
 74            if (val.second!=0) {
 75              matched = false;
 76              break;
 77            }
 78          }
 79          if (matched) {
 80            _h->fill(4.009);
 81            break;
 82          }
 83        }
 84        if (matched) break;
 85      }
 86    }
 87
 88
 89    /// Normalise histograms etc., after the run
 90    void finalize() {
 91      scale(_h,crossSection()/ sumOfWeights() /picobarn);
 92    }
 93
 94    /// @}
 95
 96
 97    /// @name Histograms
 98    /// @{
 99    Histo1DPtr _h;
100    /// @}
101
102
103  };
104
105
106  RIVET_DECLARE_PLUGIN(BESIII_2012_I1126960);
107
108}