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- -> pi+ pi- pi0 eta_c
 10  class BESIII_2021_I1826422 : public Analysis {
 11  public:
 12
 13    /// Constructor
 14    RIVET_DEFAULT_ANALYSIS_CTOR(BESIII_2021_I1826422);
 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      book(_sigma, 1,1,1);
 26      for (const string& en : _sigma.binning().edges<0>()) {
 27        const double end = std::stod(en)*GeV;
 28        if (isCompatibleWithSqrtS(end)) {
 29          _ecms = en;
 30          break;
 31        }
 32      }
 33      if (_ecms.empty()) MSG_ERROR("Beam energy incompatible with analysis.");
 34    }
 35
 36    void findChildren(const Particle & p,map<long,int> & nRes, int &ncount) {
 37      for (const Particle &child : p.children()) {
 38        if (child.children().empty()) {
 39          nRes[child.pid()]-=1;
 40          --ncount;
 41        }
 42        else {
 43          findChildren(child,nRes,ncount);
 44        }
 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& chi : ufs.particles(Cuts::pid==445)) {
 59        if (chi.children().empty()) continue;
 60        map<long,int> nRes=nCount;
 61        int ncount = ntotal;
 62        findChildren(chi,nRes,ncount);
 63        if (ncount!=3) continue;
 64        bool matched = true;
 65        for (const auto& val : nRes) {
 66          if (abs(val.first)==211 || val.first==111) {
 67            if (val.second!=1) {
 68              matched = false;
 69      	      break;
 70      	    }
 71      	  }
 72      	  else if (val.second!=0) {
 73      	    matched = false;
 74      	    break;
 75      	  }
 76      	}
 77        if (matched) {
 78          _sigma->fill(_ecms);
 79          break;
 80        }
 81      }
 82    }
 83
 84
 85    /// Normalise histograms etc., after the run
 86    void finalize() {
 87      scale(_sigma,crossSection()/ sumOfWeights() /picobarn);
 88    }
 89
 90    /// @}
 91
 92
 93    /// @name Histograms
 94    /// @{
 95    BinnedHistoPtr<string> _sigma;
 96    string _ecms;
 97    /// @}
 98
 99
100  };
101
102
103  RIVET_DECLARE_PLUGIN(BESIII_2021_I1826422);
104
105}