Rivet analyses

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

namespace Rivet {


  /// @brief e+e -> rho 0 rho and rho0 phi
  class BABAR_2006_I719949 : public Analysis {
  public:

    /// Constructor
    RIVET_DEFAULT_ANALYSIS_CTOR(BABAR_2006_I719949);


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

    /// Book histograms and initialise projections before the run
    void init() {
      // Initialise and register projections
      declare(Beam(), "Beams");
      declare(UnstableParticles(Cuts::pid==113 or
                Cuts::pid==333), "UFS");
      declare(FinalState(), "FS");
      // histos
      for(unsigned int ix=0;ix<3;++ix) {
    book(_h_hel  [ix],3,1,1+ix);
    if(ix==2) continue;
    book(_h_sigma[ix],1,1,1+ix);
    book(_h_prod [ix],2,1,1+ix);
      }
    }

    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) {
      // get the axis, direction of incoming electron
      const ParticlePair& beams = apply<Beam>(event, "Beams").beams();
      Vector3 axis;
      if(beams.first.pid()>0)
    axis = beams.first .momentum().p3().unit();
      else
    axis = beams.second.momentum().p3().unit();
      // types of 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;
      }
      // loop over rho mesons
      const Particles vMesons = apply<UnstableParticles>(event, "UFS").particles();
      Particle vectors[2];
      bool matched(false);
      for (unsigned int ix=0;ix<vMesons.size();++ix) {
    if(vMesons[ix].children().empty()) continue;
    map<long,int> nRes=nCount;
    int ncount = ntotal;
    findChildren(vMesons[ix],nRes,ncount);
    matched=false;
    for (unsigned int iy=ix+1;iy<vMesons.size();++iy) {
      if(vMesons[iy].children().empty()) continue;
      if(vMesons[ix].pid()==333 && vMesons[iy].pid()==333) continue;
      map<long,int> nRes2=nRes;
      int ncount2 = ncount;
      findChildren(vMesons[iy],nRes2,ncount2);
      if(ncount2==0) {
        matched = true;
        for(auto const & val : nRes2) {
          if(val.second!=0) {
        matched = false;
        break;
          }
        }
        if(matched) {
          vectors[0] = vMesons[ix];
          vectors[1] = vMesons[iy];
          break;
        }
      }
    }
    if(matched) break;
      }
      if(!matched) vetoEvent;
      if(vectors[0].pid()==333) swap(vectors[0],vectors[1]);
      if (vectors[0].children().size()!=2) vetoEvent;
      if (vectors[1].children().size()!=2) vetoEvent;
      double cTheta = abs(axis.dot(vectors[0].momentum().p3().unit()));
      if(cTheta>0.8) vetoEvent;
      if(vectors[0].pid()==vectors[1].pid()) {
    _h_sigma[0]->fill("10.58"s);
    _h_prod [0]->fill(cTheta);
      }
      else {
    _h_sigma[1]->fill("10.58"s);
    _h_prod [1]->fill(cTheta);
      }
      // helicity angles
      double cHel[2];
      for(unsigned int ix=0;ix<2;++ix) {
    int iMeson = vectors[ix].pid() == 113 ? 211 : 321;
    Particle mP;
    if(vectors[ix].children()[0].pid()== iMeson &&
       vectors[ix].children()[1].pid()==-iMeson)
      mP = vectors[ix].children()[0];
    else if(vectors[ix].children()[1].pid()== iMeson &&
        vectors[ix].children()[0].pid()==-iMeson)
      mP = vectors[ix].children()[1];
    else
      vetoEvent;
    // boost to the rho+ rest frame
    LorentzTransform boost1 = LorentzTransform::mkFrameTransformFromBeta(vectors[ix].momentum().betaVec());
    Vector3 e1z = vectors[ix].momentum().p3().unit();
    Vector3 axis1 = boost1.transform(mP.momentum()).p3().unit();
    cHel[ix] = e1z.dot(axis1);
      }
      if(vectors[0].pid()==vectors[1].pid()) {
    _h_hel[0]->fill(cHel[0]);
    _h_hel[0]->fill(cHel[1]);
      }
      else {
    _h_hel[1]->fill(cHel[1]);
    _h_hel[2]->fill(cHel[0]);
      }
    }


    /// Normalise histograms etc., after the run
    void finalize() {
      double fact = crossSection()/sumOfWeights()/femtobarn;
      for(unsigned int ix=0;ix<3;++ix) {
    normalize(_h_hel  [ix],1.,false);
    if(ix==2) continue;
    scale(_h_sigma[ix],fact);
    normalize(_h_prod [ix],1.,false);
      }
    }

    /// @}


    /// @name Histograms
    /// @{
    BinnedHistoPtr<string> _h_sigma[2];
    Histo1DPtr _h_prod[2],_h_hel[3];
    /// @}


  };


  RIVET_DECLARE_PLUGIN(BABAR_2006_I719949);

}