Rivet analyses

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

namespace Rivet {


  /// @brief B -> Xc ell - nu_ell
  class BABAR_2009_I827787 : public Analysis {
  public:

    /// Constructor
    RIVET_DEFAULT_ANALYSIS_CTOR(BABAR_2009_I827787);


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

    /// Book histograms and initialise projections before the run
    void init() {
      // projections
      declare(UnstableParticles(Cuts::abspid==511 ||
                Cuts::abspid==521),"UFS");
      // histograms
      for(unsigned int ix=0;ix<6;++ix) {
    book(_p_X[ix],1,1,1+ix);
    if(ix<3) book(_p_n[ix],2,1,1+ix);
      }
    }
    void findDecayProducts(Particle parent, Particles & em, Particles & ep,
               Particles & nue, Particles & nueBar, bool & charm) {
      for(const Particle & p : parent.children()) {
    if(PID::isCharmHadron(p.pid())) {
      charm=true;
    }
    else if(p.pid() == PID::EMINUS || p.pid()==PID::MUON) {
      em.push_back(p);
    }
    else if(p.pid() == PID::EPLUS || p.pid()==PID::ANTIMUON) {
      ep.push_back(p);
    }
    else if(p.pid() == PID::NU_E  || p.pid()==PID::NU_MU) {
      nue.push_back(p);
    }
    else if(p.pid() == PID::NU_EBAR || p.pid()==PID::NU_MUBAR) {
      nueBar.push_back(p);
    }
    else if(PID::isBottomHadron(p.pid())) {
      findDecayProducts(p,em,ep,nue,nueBar,charm);
    }
    else if(!PID::isHadron(p.pid())) {
      findDecayProducts(p,em,ep,nue,nueBar,charm);
    }
      }
    }

    /// Perform the per-event analysis
    void analyze(const Event& event) {
      if(_edges.empty()) _edges = _p_X[0]->xEdges();
      static const double Lambda=0.65*GeV;
      // find and loop over Upslion(4S)
      for (const Particle& p : apply<UnstableParticles>(event, "UFS").particles()) {
    if(p.children().empty() ||
       (p.children().size()==1 && p.children()[1].abspid()==p.abspid()))
      continue;
    // find decay products
    bool charm = false;
    Particles em,ep,nue,nueBar;
    findDecayProducts(p,em,ep,nue,nueBar,charm);
    if(!charm) continue;
    FourMomentum pl,pnu;
    if(em.size()==1 && nueBar.size()==1 && em[0].pid()+1==-nueBar[0].pid()) {
      pl  = em[0].momentum();
      pnu = nueBar[0].momentum();
    }
    else if(ep.size()==1 && nue.size()==1 && nue[0].pid()==-ep[0].pid()+1) {
      pl  = ep[0].momentum();
      pnu = nue[0].momentum();
        }
    else
      continue;
    // boost to rest frame
    LorentzTransform boost = LorentzTransform::mkFrameTransformFromBeta(p.momentum().betaVec());
    FourMomentum pX = boost.transform(p.momentum()-pl-pnu);
    pl = boost.transform(pl);
    double modp = pl.p3().mod();
    double mX  = pX.mass();
    double nX2 = sqr(mX)-2.*Lambda*pX.t()+sqr(Lambda);
    double m1=mX,m2=nX2;
    for(unsigned int ix=0;ix<6;++ix) {
          double Emin = 0.8;
          for(unsigned int iy=0;iy<_edges.size();++iy) {
            if(modp>Emin) _p_X[ix]->fill(_edges[iy],m1);
            Emin+=0.1;
          }
          m1 *=mX;
          if(ix>=3) continue;
          Emin = 0.8;
          for(unsigned int iy=0;iy<_edges.size();++iy) {
        if(modp>Emin) _p_n[ix]->fill(_edges[iy],m2);
            Emin+=0.1;
          }
      m2 *=nX2;
    }
      }
    }


    /// Normalise histograms etc., after the run
    void finalize() {
    }

    /// @}


    /// @name Histograms
    /// @{
    BinnedProfilePtr<string> _p_X[6],_p_n[3];
    vector<string> _edges;
    /// @}


  };


  RIVET_DECLARE_PLUGIN(BABAR_2009_I827787);

}