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 Lambda Lambdabar cross section
 10  class BESIII_2023_I2642062 : public Analysis {
 11  public:
 12
 13    /// Constructor
 14    RIVET_DEFAULT_ANALYSIS_CTOR(BESIII_2023_I2642062);
 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"); declare(UnstableParticles(), "UFS");
 24      book(_sigmaLambda,"TMP/sigma", refData(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()]-=1;
 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      // total hadronic and muonic cross sections
 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      // find the Lambdas
 50      const FinalState& ufs = apply<UnstableParticles>(event, "UFS");
 51      for (unsigned int ix=0; ix<ufs.particles().size(); ++ix) {
 52        const Particle& p1 = ufs.particles()[ix];
 53        if (abs(p1.pid())!=3122) continue;
 54        bool matched = false;
 55        // check fs
 56        bool fs = true;
 57        for (const Particle& child : p1.children()) {
 58          if (child.pid()==p1.pid()) {
 59            fs = false;
 60            break;
 61          }
 62        }
 63        if (!fs) continue;
 64        // find the children
 65        map<long,int> nRes = nCount;
 66        int ncount = ntotal;
 67        findChildren(p1,nRes,ncount);
 68        for (unsigned int iy=ix+1;iy<ufs.particles().size();++iy) {
 69          const Particle& p2 = ufs.particles()[iy];
 70          if (abs(p2.pid())!=3122) continue;
 71          // check fs
 72          bool fs = true;
 73          for (const Particle& child : p2.children()) {
 74            if (child.pid()==p2.pid()) {
 75              fs = false;
 76              break;
 77            }
 78          }
 79          if (!fs) continue;
 80          map<long,int> nRes2 = nRes;
 81          int ncount2 = ncount;
 82          findChildren(p2,nRes2,ncount2);
 83          if (ncount2!=0) continue;
 84          matched=true;
 85          for (const auto& val : nRes2) {
 86            if (val.second!=0) {
 87              matched = false;
 88              break;
 89            }
 90          }
 91          if (matched) {
 92	    _sigmaLambda->fill(sqrtS());
 93            break;
 94          }
 95        }
 96        if (matched) break;
 97      }
 98    }
 99
100
101    /// Normalise histograms etc., after the run
102    void finalize() {
103      scale(_sigmaLambda,crossSection()/ sumOfWeights() /picobarn);
104      Estimate1DPtr tmp;
105      book(tmp,1,1,1);
106      barchart(_sigmaLambda,tmp);
107    }
108
109    /// @}
110
111
112    /// @name Histograms
113    /// @{
114    Histo1DPtr _sigmaLambda;
115    /// @}
116
117
118  };
119
120
121  RIVET_DECLARE_PLUGIN(BESIII_2023_I2642062);
122
123}