Rivet analyses

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

namespace Rivet {


  /// @brief cross section for e+e- -> 2pi+ 2pi- pi0 and rho0 omega
  class ARGUS_1987_I247567 : public Analysis {
  public:

    /// Constructor
    RIVET_DEFAULT_ANALYSIS_CTOR(ARGUS_1987_I247567);


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

    /// Book histograms and initialise projections before the run
    void init() {
      // Initialise and register projections
      declare(FinalState(), "FS");
      declare(UnstableParticles(Cuts::pid == 113 || Cuts::pid == 223), "UFS");
      // histos
      for (size_t ix = 0; ix < 2; ++ix) {
        book(_c[ix], 1 + ix, 1, 1);
        for (const string& en : _c[ix].binning().edges<0>()) {
          const size_t idx = en.find("-");
          if (idx != std::string::npos) {
            const double emin = std::stod(en.substr(0, idx));
            const double emax = stod(en.substr(idx + 1, string::npos));
            if (inRange(sqrtS() / GeV, emin, emax)) {
              _sqs[ix] = en;
              break;
            }
          }
          else {
            const double eval = stod(en) * GeV;
            if (isCompatibleWithSqrtS(eval)) {
              _sqs[ix] = en;
              break;
            }
          }
        }
      }
      raiseBeamErrorIf(_sqs[0].empty() && _sqs[1].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()] -= 1;
          --ncount;
        }
        else {
          findChildren(child, nRes, ncount);
        }
      }
    }


    /// Perform the per-event analysis
    void analyze(const Event& event) {
      const FinalState& fs = apply<FinalState>(event, "FS");
      // find the final-state particles
      map<long, int> nCount;
      int ntotal(0);
      for (const Particle& p : fs.particles()) {
        nCount[p.pid()] += 1;
        ++ntotal;
      }
      if (ntotal == 5 && nCount[211] == 2 && nCount[-211] == 2 && nCount[111] == 1) _c[0]->fill(_sqs[0]);
      // rho0 mesons
      const UnstableParticles& ufs = apply<UnstableParticles>(event, "UFS");
      for (const Particle& rho : ufs.particles(Cuts::pid == 113)) {
        if (rho.children().empty()) continue;
        map<long, int> nRes = nCount;
        int ncount = ntotal;
        findChildren(rho, nRes, ncount);
        bool matched = false;
        // omega
        for (const Particle& omega : ufs.particles(Cuts::pid == 223)) {
          if (omega.children().empty()) continue;
          map<long, int> nRes2 = nRes;
          int ncount2 = ncount;
          findChildren(omega, nRes2, ncount2);
          if (ncount2 != 0) continue;
          matched = true;
          for (const auto& val : nRes2) {
            if (val.second != 0) {
              matched = false;
              break;
            }
          }
          if (matched) {
            _c[1]->fill(_sqs[1]);
            break;
          }
        }
        if (matched) break;
      }
    }


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

    /// @}


    /// @name Histograms
    /// @{
    BinnedHistoPtr<string> _c[2];
    string _sqs[2];
    /// @}
  };


  RIVET_DECLARE_PLUGIN(ARGUS_1987_I247567);

}