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_I527752 : public Analysis {
  public:

    /// Constructor
    RIVET_DEFAULT_ANALYSIS_CTOR(SND_2000_I527752);


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

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

      // Initialise and register projections
      declare(FinalState(), "FS");
      declare(UnstableParticles(), "UFS");
      book(_numOmegaPi, 1, 1, 1);
      for (const string& en : _numOmegaPi.binning().edges<0>()) {
        const size_t idx = en.find("-");
        if (idx != string::npos) {
          const double emin = stod(en.substr(0, idx));
          const double emax = stod(en.substr(idx + 1, string::npos));
          if (inRange(sqrtS() / MeV, emin, emax)) {
            _sqs = en;
            break;
          }
        }
        else {
          const double end = stod(en) * MeV;
          if (isCompatibleWithSqrtS(end)) {
            _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()] += 1;
          ++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;
      }
      // three particles (pi0 pi0 gamma)
      if (ntotal != 3) vetoEvent;
      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;
          int ncount(0);
          findChildren(p, nRes, ncount);
          // only omega to pi0 gamma mode
          if (ncount != 2) continue;
          if (nRes[111] != 1 || nRes[22] != 1) continue;
          // omega pi0
          if (nCount[111] - nRes[111] == 1) _numOmegaPi->fill(_sqs);
        }
      }
    }


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

    /// @}

    /// @name Histograms
    /// @{
    BinnedHistoPtr<string> _numOmegaPi;
    string _sqs = "";
    /// @}
  };


  RIVET_DECLARE_PLUGIN(SND_2000_I527752);
}