Rivet analyses

// -*- C++ -*-
#include "Rivet/Analysis.hh"
#include "Rivet/Projections/FinalState.hh"
#include "Rivet/Projections/UnstableParticles.hh"


namespace Rivet {


  /// @brief Add a short analysis description here
  class SND_2000_I524221 : public Analysis {
  public:

    /// Constructor
    RIVET_DEFAULT_ANALYSIS_CTOR(SND_2000_I524221);


    /// @name Analysis methods
    /// @{

    /// Book histograms and initialise projections before the run
    void init() {

      // Initialise and register projections
      declare(FinalState(), "FS");
      declare(UnstableParticles(), "UFS");
      book(_numEtaGamma, "TMP/EtaGamma");
      book(_numPi0Gamma, "TMP/Pi0Gamma");
    }

    void findChildren(const Particle & p,map<long,int> & nRes, int &ncount) {
      for (const Particle &child : p.children()) {
    if(child.children().empty()) {
      --nRes[child.pid()];
      --ncount;
    }
    else
      findChildren(child,nRes,ncount);
      }
    }

    /// Perform the per-event analysis
    void analyze(const Event& event) {

      const FinalState& fs = apply<FinalState>(event, "FS");

      map<long,int> nCount;
      int ntotal(0);
      for (const Particle& p : fs.particles()) {
    nCount[p.pid()] += 1;
    ++ntotal;
      }
      if(ntotal==2 && nCount[22]==1 && nCount[111]==1)
    _numPi0Gamma->fill();


      const FinalState& ufs = apply<FinalState>(event, "UFS");
      for (const Particle& p : ufs.particles()) {
    if(p.children().empty()) continue;
    // find the eta
    if(p.pid()==221) {
      map<long,int> nRes = nCount;
      int ncount = ntotal;
      findChildren(p,nRes,ncount);
      // eta pi+pi-
      if(ncount!=1) continue;
      bool matched = true;
      for(auto const & val : nRes) {
        if(val.first==22) {
          if(val.second !=1) {
        matched = false;
        break;
          }
        }
        else if(val.second!=0) {
          matched = false;
          break;
        }
      }
      if(matched)
        _numEtaGamma->fill();
    }
      }
    }


    /// Normalise histograms etc., after the run
    void finalize() {
      for (unsigned int ix=1;ix<3;++ix) {
        double sigma,error;
        if(ix==1) {
          sigma = _numEtaGamma->val();
          error = _numEtaGamma->err();
        }
        else {
          sigma = _numPi0Gamma->val();
          error = _numPi0Gamma->err();
        }
        sigma *= crossSection()/ sumOfWeights() /nanobarn;
        error *= crossSection()/ sumOfWeights() /nanobarn;
        Estimate1DPtr mult;
        book(mult, 1, 1, ix);
        for (auto& b : mult->bins()) {
          if (inRange(sqrtS()/MeV, b.xMin(), b.xMax())) {
            b.set(sigma, error);
          }
        }
      }
    }

    /// @}


    /// @name Histograms
    /// @{
    CounterPtr _numEtaGamma,_numPi0Gamma;
    /// @}


  };


  RIVET_DECLARE_PLUGIN(SND_2000_I524221);


}