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_2018_I1627871 : public Analysis {
 11  public:
 12
 13    /// Constructor
 14    RIVET_DEFAULT_ANALYSIS_CTOR(BESIII_2018_I1627871);
 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(_nLambda, "/TMP/nLambda" );
 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()]-=1;
 32          --ncount;
 33        }
 34        else
 35          findChildren(child,nRes,ncount);
 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(auto const & val : nRes2) {
 86            if(val.second!=0) {
 87              matched = false;
 88              break;
 89            }
 90          }
 91          if(matched) {
 92            _nLambda->fill();
 93            break;
 94          }
 95        }
 96        if(matched) break;
 97      }
 98    }
 99
100
101    /// Normalise histograms etc., after the run
102    void finalize() {
103      double sigma = _nLambda->val();
104      double error = _nLambda->err();
105      sigma *= crossSection()/ sumOfWeights() /picobarn;
106      error *= crossSection()/ sumOfWeights() /picobarn;
107      Estimate1D temphisto(refData(1, 1, 1));
108      Estimate1DPtr  mult;
109      book(mult, 1, 1, 1);
110      for (auto& b : mult->bins()) {
111        if (inRange(sqrtS()/GeV, b.xMin(), b.xMax())) {
112          b.set(sigma, error);
113        }
114      }
115    }
116    /// @}
117
118    /// @name Histograms
119    /// @{
120    CounterPtr _nLambda;
121    /// @}
122  };
123
124
125  RIVET_DECLARE_PLUGIN(BESIII_2018_I1627871);
126
127
128}