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_2020_I1762922 : public Analysis {
 11  public:
 12
 13    /// Constructor
 14    RIVET_DEFAULT_ANALYSIS_CTOR(BESIII_2020_I1762922);
 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(_nJPsi, "TMP/JPsi");
 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    /// Perform the per-event analysis
 39    void analyze(const Event& event) {
 40      const FinalState& fs = apply<FinalState>(event, "FS");
 41      map<long,int> nCount;
 42      int ntotal(0);
 43      for (const Particle& p : fs.particles()) {
 44        nCount[p.pid()] += 1;
 45        ++ntotal;
 46      }
 47      const FinalState& ufs = apply<FinalState>(event, "UFS");
 48      for (const Particle& p : ufs.particles()) {
 49        if(p.children().empty()) continue;
 50        // find the h_c
 51        if(p.pid()==443) {
 52          map<long,int> nRes = nCount;
 53          int ncount = ntotal;
 54          findChildren(p,nRes,ncount);
 55          // omega pi+pi-
 56          if(ncount!=2) continue;
 57          bool matched = true;
 58          for(auto const & val : nRes) {
 59            if(abs(val.first)==331) {
 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            _nJPsi->fill();
 72            break;
 73          }
 74        }
 75      }
 76    }
 77
 78
 79    /// Normalise histograms etc., after the run
 80    void finalize() {
 81      double sigma = _nJPsi->val();
 82      double error = _nJPsi->err();
 83      sigma *= crossSection()/ sumOfWeights() /picobarn;
 84      error *= crossSection()/ sumOfWeights() /picobarn;
 85      Estimate1DPtr  mult;
 86      book(mult, 1, 1, 1);
 87      for (auto& b : mult->bins()) {
 88        if (inRange(sqrtS()/GeV, b.xMin(), b.xMax())) {
 89          b.set(sigma, error);
 90        }
 91      }
 92    }
 93
 94    /// @}
 95
 96
 97    /// @name Histograms
 98    /// @{
 99    CounterPtr _nJPsi;
100    /// @}
101
102  };
103
104
105
106  RIVET_DECLARE_PLUGIN(BESIII_2020_I1762922);
107
108}