Rivet analyses

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

namespace Rivet {


  /// @brief e+e- > eta pi0 gamma
  class SND_2020_I1800477 : public Analysis {
  public:

    /// Constructor
    RIVET_DEFAULT_ANALYSIS_CTOR(SND_2020_I1800477);


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

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

      // Initialise and register projections
      declare(FinalState(), "FS");
      declare(UnstableParticles(), "UFS");
      book(_c_omega, "/TMP/omega", refData(1,1,1));
      book(_c_total, "/TMP/total", refData(3,1,1));
    }

    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;
      }
      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) continue;
    map<long,int> nRes = nCount;
    int ncount = ntotal;
    findChildren(p,nRes,ncount);
    // check eta pi0 gamma FS
    if(ncount!=2) continue;
    bool matched=true;
    for(auto const & val : nRes) {
      if(abs(val.first)==22 || val.first==111 ) {
        if(val.second !=1) {
          matched = false;
          break;
        }
      }
      else if(val.second!=0) {
        matched = false;
        break;
      }
    }
    if(!matched) continue;
    _c_total->fill(sqrtS());
    // check if from omega
    for (const Particle& p2 : ufs.particles()) {
      if(p2.pid()!=223) continue;
      map<long,int> nResB = nRes;
      int ncountB = ncount;
      findChildren(p2,nResB,ncountB);
      if(ncountB!=0) continue;
      bool matched2 = true;
      for(auto const & val : nResB) {
        if(val.second!=0) {
          matched2 = false;
          break;
        }
      }
      if(matched2)
        _c_omega->fill(sqrtS());
    }
      }
    }


    /// Normalise histograms etc., after the run
    void finalize() {
      double fact = crossSection()/picobarn/sumOfWeights();
      scale(_c_total,fact);
      Estimate1DPtr  mult;
      book(mult, 1, 1, 1);
      barchart(_c_total,mult);
      scale(_c_omega,fact);
      book(mult, 3, 1, 1);
      barchart(_c_omega,mult);
    }

    /// @}


    /// @name Histograms
    /// @{
    Histo1DPtr _c_total,_c_omega;
    /// @}


  };


  RIVET_DECLARE_PLUGIN(SND_2020_I1800477);

}