Rivet analyses

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

namespace Rivet {


  /// @brief B -> Xs gamma
  class BELLE_2009_I825222 : public Analysis {
  public:

    /// Constructor
    RIVET_DEFAULT_ANALYSIS_CTOR(BELLE_2009_I825222);


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

    /// Book histograms and initialise projections before the run
    void init() {
      // Initialise and register projections
      declare(UnstableParticles(Cuts::abspid==521 || Cuts::abspid==511), "UFS");
      // Book histograms
      book(_h_br, 1, 1, 1);
      book(_p_E,  1, 1, 2);
      book(_p_E2,"TMP/E2",refData<YODA::BinnedEstimate<string>>(1,1,3));
      book(_nBottom, "TMP/BottomCounter");
    }

    void findDecayProducts(const Particle& mother,
                           unsigned int& nK0, unsigned int& nKp,
               unsigned int& nKm) {
      for (const Particle & p : mother.children()) {
        int id = p.pid();
        if ( id == PID::KPLUS )      ++nKp;
        else if (id == PID::KMINUS ) ++nKm;
        else if (id == PID::K0S)     ++nK0;
        else if (id == PID::PI0 || id == PID::PIPLUS || id == PID::PIMINUS) {
      continue;
        }
        else if ( !p.children().empty() ) {
          findDecayProducts(p, nK0, nKp, nKm);
        } 
      }
    }

    /// Perform the per-event analysis
    void analyze(const Event& event) {
      if(_edges.empty()) {
        _edges = _h_br->xEdges();
        for(const string & en : _edges)
          _eCut.push_back(std::stod(en)*GeV);
      }
      // Loop over bottoms
      for (const Particle& bottom : apply<UnstableParticles>(event, "UFS").particles()) {
    // remove mixing entries etc
    if(bottom.children()[0].abspid()==bottom.abspid()) continue;
        _nBottom->fill();
    FourMomentum pgamma(0.,0.,0.,0.);
    unsigned int ngamma = 0;
        for (const Particle & child : bottom.children()) {
      if (child.pid() == PID::PHOTON) {
            ngamma += 1;
            pgamma += child.momentum();
          }
    }
    if (ngamma != 1) continue;
        unsigned int nK0(0),nKp(0),nKm(0);
        FourMomentum p_tot(0,0,0,0);
        findDecayProducts(bottom, nK0, nKp, nKm);
        unsigned int nk = nKp-nKm+nK0;
        if (nk % 2 == 1) {
          const LorentzTransform boost = LorentzTransform::mkFrameTransformFromBeta(bottom.momentum().betaVec());
          double eGamma = boost.transform(pgamma).E();
          for(unsigned int ix=0;ix<_eCut.size();++ix) {
            if(eGamma>_eCut[ix]) {
              _h_br->fill(_edges[ix]);
              _p_E ->fill(_edges[ix],eGamma);
              _p_E2->fill(_edges[ix],sqr(eGamma));
            }
          }
        }
      }
    }


    /// Normalise histograms etc., after the run
    void finalize() {
      // 1e4 for br ormalization
      scale(_h_br, 1e4/_nBottom->sumW());
      // dispersion
      BinnedEstimatePtr<string> dispersion;
      book(dispersion,1,1,3);
      for (auto& b : dispersion->bins()) {
        const auto& bE  = _p_E->bin(b.index());
        const auto& bE2 = _p_E2->bin(b.index());
        const double val = bE2.mean(2)-sqr(bE.mean(2));
        const double err = val*sqrt(sqr(bE2.stdErr(2)/bE2.mean(2))+4.*sqr(bE.stdErr(2)/bE.mean(2)));
        b.set(val,err);
      }
    }

    /// @}


    /// @name Histograms
    /// @{
    BinnedHistoPtr<string> _h_br;
    BinnedProfilePtr<string> _p_E,_p_E2;
    CounterPtr _nBottom;
    vector<string> _edges;
    vector<double> _eCut;
    /// @}


  };


  RIVET_DECLARE_PLUGIN(BELLE_2009_I825222);

}