Rivet analyses

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

namespace Rivet {


  /// @brief B -> phi phi K
  class BABAR_2011_I901433 : public Analysis {
  public:

    /// Constructor
    RIVET_DEFAULT_ANALYSIS_CTOR(BABAR_2011_I901433);


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

    /// Book histograms and initialise projections before the run
    void init() {
      UnstableParticles ufs = UnstableParticles(Cuts::abspid==511 or
                        Cuts::abspid==521);
      declare(ufs, "UFS");
      DecayedParticles BB(ufs);
      BB.addStable(PID::PHI);
      BB.addStable(PID::K0S);
      declare(BB, "BB");
      // histograms
      for(unsigned int ix=0;ix<6;++ix)
    book(_h[ix],1,1,1+ix);
    }

    /// Perform the per-event analysis
    void analyze(const Event& event) {
      DecayedParticles BB = apply<DecayedParticles>(event, "BB");
      static const map<PdgId,unsigned int> & mode1   = { { 333,2},{ 321,1}};
      static const map<PdgId,unsigned int> & mode1CC = { { 333,2},{-321,1}};
      static const map<PdgId,unsigned int> & mode2   = { { 333,2},{ 310,1}};
      for(unsigned int ix=0;ix<BB.decaying().size();++ix) {
    if(BB.modeMatches(ix,3,mode1) || BB.modeMatches(ix,3,mode1CC) ||
       BB.modeMatches(ix,3,mode2)) {
      // phi mesons
      const Particles & phi = BB.decayProducts()[ix].at(333);
      // bost to B rest frane
      LorentzTransform boost1 = LorentzTransform::mkFrameTransformFromBeta(BB.decaying()[ix].momentum().betaVec());
      FourMomentum pPhiPhi= boost1.transform(phi[0].momentum()+phi[1].momentum());
      double mPhiPhi = pPhiPhi.mass();
      int iloc=-1;
      if(mPhiPhi>2.94 && mPhiPhi<3.02)
        iloc=0;
      else if(mPhiPhi<2.85)
        iloc=3;
      else continue;
      // cos theta phi phi
      Vector3 axis1 = pPhiPhi.p3().unit();
      LorentzTransform boost2 = LorentzTransform::mkFrameTransformFromBeta(pPhiPhi.betaVec());
      Vector3 axis2 = boost2.transform(boost1.transform(phi[0].momentum())).p3().unit();
      _h[iloc+2]->fill(abs(axis1.dot(axis2)));
      // now for the phi decays
      Vector3 Trans[2];
      bool foundPhi=true;
      for(unsigned int ix=0;ix<2;++ix) {
        if(phi[ix].children().size()!=2|| phi[ix].children()[0].pid()!=-phi[ix].children()[1].pid() ||
           phi[ix].children()[0].abspid()!=321) {
          foundPhi = false;
          break;
        }
        Particle Km = phi[ix].children()[0];
        Particle Kp = phi[ix].children()[1];
        if(Kp.pid()<0) swap(Km,Kp);
        FourMomentum pKp  = boost2.transform(boost1.transform(Kp.momentum()));
        FourMomentum pPhi = boost2.transform(boost1.transform(phi[ix].momentum()));
        LorentzTransform boost3 = LorentzTransform::mkFrameTransformFromBeta(pPhi.betaVec());
        pKp = boost3.transform(pKp);
        double cK = axis2.dot(pKp.p3().unit());
        _h[iloc+1]->fill(cK);
        Trans[ix] = pKp.p3() - cK*pKp.p3().mod()*axis2;
      }
      if(!foundPhi) continue;
      double chi = atan2(Trans[0].cross(Trans[1]).dot(axis2),Trans[0].dot(Trans[1]));
      _h[iloc]->fill(abs(chi));
    }
      }
    }


    /// Normalise histograms etc., after the run
    void finalize() {
      for(unsigned int ix=0;ix<6;++ix)
    normalize(_h[ix],1.,false);
    }

    /// @}


    /// @name Histograms
    /// @{
    Histo1DPtr _h[6];
    /// @}


  };


  RIVET_DECLARE_PLUGIN(BABAR_2011_I901433);

}