Rivet analyses

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

namespace Rivet {


  /// @brief CMD3 pi+pi-pi0eta cross section
  class CMD3_2017_I1606078 : public Analysis {
  public:

    /// Constructor
    RIVET_DEFAULT_ANALYSIS_CTOR(CMD3_2017_I1606078);


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

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

      // Initialise and register projections
      declare(FinalState(), "FS");
      declare(UnstableParticles(), "UFS");


      book(_c_all, 1, 1, 1);
      book(_c_omega, 1, 1, 2);
      book(_c_rho, 1, 1, 3);
      book(_c_other, 1, 1, 4);
    }

    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) {
      // find the 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;
      }
      // find omega/phi + eta
      const FinalState& ufs = apply<FinalState>(event, "UFS");
      bool found = false, foundOmegaPhi = false;
      for (const Particle& p : ufs.particles()) {
        if (p.children().empty()) continue;
        // find the eta
        if (p.pid() != 221) continue;
        map<long, int> nRes = nCount;
        int ncount = ntotal;
        findChildren(p, nRes, ncount);
        // eta pi+pi-pi0
        if (ncount == 3) {
          bool matched = true;
          for (const auto& val : nRes) {
            if (abs(val.first) == 211 || val.first == 111) {
              if (val.second != 1) {
                matched = false;
                break;
              }
            }
            else if (val.second != 0) {
              matched = false;
              break;
            }
          }
          if (matched) {
            _c_all->fill(round(sqrtS() / MeV));
            found = true;
          }
        }
        for (const Particle& p2 : ufs.particles()) {
          if (p2.pid() != 223 && p2.pid() != 333) continue;
          map<long, int> nResB = nRes;
          int ncountB = ncount;
          findChildren(p2, nResB, ncountB);
          if (ncountB != 0) continue;
          bool matched2 = true;
          for (const auto& val : nResB) {
            if (val.second != 0) {
              matched2 = false;
              break;
            }
          }
          if (matched2) {
            if (p2.pid() == 223) _c_omega->fill(round(sqrtS() / MeV));
            foundOmegaPhi = true;
          }
        }
      }
      // find a_0 rho
      bool founda0Rho = false;
      for (const Particle& p : ufs.particles()) {
        if (p.children().empty()) continue;
        // find the rho
        if (p.pid() != 113 && abs(p.pid()) != 213) continue;
        map<long, int> nRes = nCount;
        int ncount = ntotal;
        findChildren(p, nRes, ncount);
        int a1id(0);
        if (p.pid() == 213)
          a1id = 9000211;
        else if (p.pid() == -213)
          a1id = -9000211;
        else
          a1id = 9000111;
        for (const Particle& p2 : ufs.particles()) {
          if (p2.pid() != a1id) continue;
          map<long, int> nResB = nRes;
          int ncountB = ncount;
          findChildren(p2, nResB, ncountB);
          if (ncountB != 0) continue;
          bool matched = true;
          for (const auto& val : nResB) {
            if (val.second != 0) {
              matched = false;
              break;
            }
          }
          if (matched) {
            _c_rho->fill(round(sqrtS() / MeV));
            founda0Rho = true;
            break;
          }
        }
        if (founda0Rho) break;
      }
      if (found && !foundOmegaPhi && !founda0Rho) _c_other->fill(round(sqrtS() / MeV));
    }


    /// Normalise histograms etc., after the run
    void finalize() {
      double fact = crossSection() / nanobarn / sumOfWeights();
      scale(_c_all, fact);
      scale(_c_omega, fact);
      scale(_c_rho, fact);
      scale(_c_other, fact);
    }

    /// @}


    /// @name Histograms
    /// @{
    BinnedHistoPtr<int> _c_all, _c_omega, _c_rho, _c_other;
    /// @}
  };


  RIVET_DECLARE_PLUGIN(CMD3_2017_I1606078);


}