Rivet analyses

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


namespace Rivet {


  /// @brief e+e- -> 4 pions
  class CMD2_1999_I483994 : public Analysis {
  public:

    /// Constructor
    RIVET_DEFAULT_ANALYSIS_CTOR(CMD2_1999_I483994);


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

    /// Book histograms and initialise projections before the run
    void init() {
      // Initialise and register projections
      declare(FinalState(), "FS");
      declare(UnstableParticles(), "UFS");
      book(_ncharged, 1, 1, 1);
      book(_nneutral, 2, 1, 1);
      book(_nomega, 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;
      }
      if (ntotal == 4) {
        if (nCount[211] == 2 && nCount[-211] == 2)
          _ncharged->fill(round(sqrtS() / MeV));
        else if (nCount[211] == 1 && nCount[-211] == 1 && nCount[111] == 2)
          _nneutral->fill(round(sqrtS() / MeV));
      }


      const FinalState& ufs = apply<FinalState>(event, "UFS");
      for (const Particle& p : ufs.particles()) {
        if (p.children().empty()) continue;
        // find the omega
        if (p.pid() == 223) {
          map<long, int> nRes = nCount;
          int ncount = ntotal;
          findChildren(p, nRes, ncount);
          // omega pi+pi-
          if (ncount != 1) continue;
          bool matched = true;
          for (const auto& val : nRes) {
            if (abs(val.first) == 111) {
              if (val.second != 1) {
                matched = false;
                break;
              }
            }
            else if (val.second != 0) {
              matched = false;
              break;
            }
          }
          if (matched) _nomega->fill(round(sqrtS() / MeV));
        }
      }
    }


    /// Normalise histograms etc., after the run
    void finalize() {
      double fact = crossSection() / sumOfWeights() / nanobarn;
      scale(_ncharged, fact);
      scale(_nneutral, fact);
      scale(_nomega, fact);
    }

    /// @}


    /// @name Histograms
    /// @{
    BinnedHistoPtr<int> _ncharged, _nneutral, _nomega;
    /// @}
  };


  RIVET_DECLARE_PLUGIN(CMD2_1999_I483994);


}