Rivet analyses

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

namespace Rivet {


  /// @brief e+e-> D_s D_s*
  class MARKIII_1987_I244856 : public Analysis {
  public:

    /// Constructor
    RIVET_DEFAULT_ANALYSIS_CTOR(MARKIII_1987_I244856);


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

    /// Book histograms and initialise projections before the run
    void init() {
      // Initialise and register projections
      declare(FinalState(), "FS");
      declare(UnstableParticles(Cuts::abspid == 431 or Cuts::abspid == 433), "UFS");
      // histos
      book(_h, 1, 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()] -= 1;
          --ncount;
        }
        else {
          findChildren(child, nRes, ncount);
        }
      }
    }

    /// Perform the per-event analysis
    void analyze(const Event& event) {
      const FinalState& fs = apply<FinalState>(event, "FS");
      // total hadronic and muonic cross sections
      map<long, int> nCount;
      int ntotal(0);
      for (const Particle& p : fs.particles()) {
        nCount[p.pid()] += 1;
        ++ntotal;
      }
      // mu+mu- + photons
      if (nCount[-13] == 1 and nCount[13] == 1 && ntotal == 2 + nCount[22]) vetoEvent;
      Particles ds = apply<UnstableParticles>(event, "UFS").particles();
      for (const Particle& p1 : ds) {
        if (p1.abspid() != 431) continue;
        // find the children
        bool matched = false;
        map<long, int> nRes = nCount;
        int ncount = ntotal;
        findChildren(p1, nRes, ncount);
        for (const Particle& p2 : ds) {
          if (p2.abspid() != 433 || p1.pid() * p2.pid() > 0) continue;
          map<long, int> nRes2 = nRes;
          int ncount2 = ncount;
          findChildren(p2, nRes2, ncount2);
          if (ncount2 != 0) continue;
          matched = true;
          for (const auto& val : nRes2) {
            if (val.second != 0) {
              matched = false;
              break;
            }
          }
          if (matched) {
            break;
          }
        }
        if (matched) {
          _h->fill("4.14"s);
          break;
        }
      }
    }


    /// Normalise histograms etc., after the run
    void finalize() {
      const double br = 0.045;
      const double fact = br * crossSection() / sumOfWeights() / picobarn;
      scale(_h, fact);
    }

    /// @}


    /// @name Histograms
    /// @{
    BinnedHistoPtr<string> _h;
    /// @}
  };


  RIVET_DECLARE_PLUGIN(MARKIII_1987_I244856);

}