Rivet analyses

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

namespace Rivet {


  /// @brief e+ e- > omega pi0, rho eta(')
  class BESII_2004_I661567 : public Analysis {
  public:

    /// Constructor
    RIVET_DEFAULT_ANALYSIS_CTOR(BESII_2004_I661567);


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

    /// Book histograms and initialise projections before the run
    void init() {
      // projection
      declare(FinalState(), "FS");
      declare(UnstableParticles(), "UFS");
      // counter
      for (size_t ix = 0; ix < 3; ++ix) {
        book(_sigma[ix], 1, 1, 1 + ix);
      }

      for (const string& en : _sigma[0].binning().edges<0>()) {
        double eval = stod(en) * GeV;
        if (isCompatibleWithSqrtS(eval)) {
          _sqs = en;
          break;
        }
      }
      raiseBeamErrorIf(_sqs.empty());
    }

    void findChildren(const Particle& p, map<long, int>& nRes, int& ncount) const {
      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) {
      // final state particles
      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 UnstableParticles& ufs = apply<UnstableParticles>(event, "UFS");
      // first the omega pi0 final state
      bool matched = false;
      for (const Particle& p : ufs.particles(Cuts::pid == 223)) {
        if (p.children().empty()) continue;
        map<long, int> nRes = nCount;
        int ncount = ntotal;
        findChildren(p, nRes, ncount);
        if (ncount == 1) {
          matched = true;
          for (const auto& val : nRes) {
            if (val.first == 111) {
              if (val.second != 1) {
                matched = false;
                break;
              }
            }
            else if (val.second != 0) {
              matched = false;
              break;
            }
          }
          if (matched) {
            _sigma[0]->fill(_sqs);
            break;
          }
        }
      }
      if (matched) return;
      // rho eta states
      for (const Particle& p : ufs.particles(Cuts::pid == 113)) {
        if (p.children().empty()) continue;
        map<long, int> nRes = nCount;
        int ncount = ntotal;
        findChildren(p, nRes, ncount);
        // check for eta/eta'
        for (const Particle& p2 : ufs.particles(Cuts::pid == 221 || Cuts::pid == 331)) {
          map<long, int> nResB = nRes;
          int ncountB = ncount;
          findChildren(p2, nResB, ncountB);
          if (ncountB != 0) continue;
          matched = true;
          for (const auto& val : nResB) {
            if (val.second != 0) {
              matched = false;
              break;
            }
          }
          if (matched) {
            if (p2.pid() == 221)
              _sigma[1]->fill(_sqs);
            else if (_sqs == "3.686")
              _sigma[2]->fill(_sqs);
            break;
          }
        }
      }
    }


    /// Normalise histograms etc., after the run
    void finalize() {
      scale(_sigma, crossSection() / picobarn / sumOfWeights());
    }

    /// @}


    /// @name Histograms
    /// @{
    BinnedHistoPtr<string> _sigma[3];
    string _sqs = "";
    /// @}
  };


  RIVET_DECLARE_PLUGIN(BESII_2004_I661567);

}