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- J/psi
 10  class BESIII_2023_I2156632 : public Analysis {
 11  public:
 12
 13    /// Constructor
 14    RIVET_DEFAULT_ANALYSIS_CTOR(BESIII_2023_I2156632);
 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      for(unsigned int ix=0;ix<3;++ix)
 25        book(_sigmaPsi[ix], "TMP/psi-" + toString(ix+1), refData(1,1,1+ix));
 26    }
 27
 28    void findChildren(const Particle& p,map<long,int>& nRes, int& ncount) {
 29      for (const Particle &child : p.children()) {
 30        if (child.children().empty()) {
 31          --nRes[child.pid()];
 32          --ncount;
 33        }
 34        else {
 35          findChildren(child,nRes,ncount);
 36        }
 37      }
 38    }
 39
 40    /// Perform the per-event analysis
 41    void analyze(const Event& event) {
 42      const FinalState& fs = apply<FinalState>(event, "FS");
 43      map<long,int> nCount;
 44      int ntotal(0);
 45      for (const Particle& p: fs.particles()) {
 46        nCount[p.pid()] += 1;
 47        ++ntotal;
 48      }
 49      const FinalState& ufs = apply<FinalState>(event, "UFS");
 50      // find the psis
 51      for (const Particle& p :  ufs.particles(Cuts::pid==443)) {
 52        if (p.children().empty()) continue;
 53        map<long,int> nRes = nCount;
 54        int ncount = ntotal;
 55        findChildren(p,nRes,ncount);
 56        // psi pi+pi-
 57        if (ncount!=2) continue;
 58        bool matched = true;
 59        for (const auto& val : nRes) {
 60          if (abs(val.first)==211) {
 61            if (val.second !=1) {
 62              matched = false;
 63              break;
 64            }
 65          }
 66          else if (val.second!=0) {
 67            matched = false;
 68            break;
 69          }
 70        }
 71        if (matched) {
 72	  for(unsigned int ix=0;ix<3;++ix) _sigmaPsi[ix]->fill(sqrtS()/MeV);
 73          break;
 74        }
 75      }
 76    }
 77
 78
 79    /// Normalise histograms etc., after the run
 80    void finalize() {
 81      for(unsigned int ix=0;ix<3;++ix) {
 82        scale(_sigmaPsi[ix],crossSection()/ sumOfWeights() /picobarn);
 83        Estimate1DPtr tmp;
 84        book(tmp,1,1,1+ix);
 85        barchart(_sigmaPsi[ix],tmp);
 86      }
 87    }
 88
 89    /// @}
 90
 91
 92    /// @name Histograms
 93    /// @{
 94    Histo1DPtr _sigmaPsi[3];
 95    /// @}
 96
 97
 98  };
 99
100
101  RIVET_DECLARE_PLUGIN(BESIII_2023_I2156632);
102
103}