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- -> pi0pi0psi(2S) for energies between 4.009 to 4.600 GeV
 10  class BESIII_2018_I1633425 : public Analysis {
 11  public:
 12
 13    /// Constructor
 14    RIVET_DEFAULT_ANALYSIS_CTOR(BESIII_2018_I1633425);
 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(_nPsi2, 1, 1, 1);
 25      for (const string& en : _nPsi2.binning().edges<0>()) {
 26        const double end = std::stod(en)*GeV;
 27        if (isCompatibleWithSqrtS(end)) {
 28          _ecms = en;
 29          break;
 30        }
 31      }
 32      if (_ecms.empty())
 33        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()];
 40          --ncount;
 41        }
 42        else
 43          findChildren(child,nRes,ncount);
 44      }
 45    }
 46
 47    /// Perform the per-event analysis
 48    void analyze(const Event& event) {
 49      const FinalState& fs = apply<FinalState>(event, "FS");
 50      map<long,int> nCount;
 51      int ntotal(0);
 52      for (const Particle& p : fs.particles()) {
 53        nCount[p.pid()] += 1;
 54        ++ntotal;
 55      }
 56      const FinalState& ufs = apply<FinalState>(event, "UFS");
 57      for (const Particle& p : ufs.particles()) {
 58        if(p.children().empty()) continue;
 59        // find the psi(2S)
 60        if(p.pid()==100443) {
 61          map<long,int> nRes = nCount;
 62          int ncount = ntotal;
 63          findChildren(p,nRes,ncount);
 64          // omega pi+pi-
 65          if(ncount!=2) continue;
 66          bool matched = true;
 67          for(auto const & val : nRes) {
 68            if(abs(val.first)==111) {
 69              if(val.second !=2) {
 70                matched = false;
 71                break;
 72              }
 73            }
 74            else if(val.second!=0) {
 75              matched = false;
 76              break;
 77            }
 78          }
 79          if(matched) {
 80            _nPsi2->fill(_ecms);
 81            break;
 82          }
 83        }
 84      }
 85    }
 86
 87    /// Normalise histograms etc., after the run
 88    void finalize() {
 89      scale(_nPsi2, crossSection()/ sumOfWeights() /picobarn);
 90    }
 91    /// @}
 92
 93
 94    /// @name Histograms
 95    /// @{
 96    BinnedHistoPtr<string> _nPsi2;
 97    string _ecms;
 98    /// @}
 99
100  };
101
102
103  RIVET_DECLARE_PLUGIN(BESIII_2018_I1633425);
104
105}