Rivet analyses

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

namespace Rivet {


  /// @brief B -> phi K pi
  class BABAR_2008_I792439 : public Analysis {
  public:

    /// Constructor
    RIVET_DEFAULT_ANALYSIS_CTOR(BABAR_2008_I792439);


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

    /// Book histograms and initialise projections before the run
    void init() {
      // Initialise and register projections
      UnstableParticles ufs = UnstableParticles(Cuts::abspid==511);
      declare(ufs, "UFS");
      DecayedParticles B0(ufs);
      B0.addStable(333);
      B0.addStable(310);
      B0.addStable(111);
      declare(B0, "B0");
      // histos
      for(unsigned int ix=0;ix<2;++ix) {
    book(_p[ix][0],1,2,2+ix);
    book(_p[ix][1],"TMP/norm_"+toString(ix));
    for(unsigned int iy=0;iy<2;++iy) {
      book(_h_mass[ix][iy],2,1+ix,1+iy);
      book(_h_angle[ix][iy],3+ix,1,1+iy);
    }
      }
    }


    /// Perform the per-event analysis
    void analyze(const Event& event) {
      static const map<PdgId,unsigned int> & mode1   = { { 321,1},{-211,1}, { 333,1}};
      static const map<PdgId,unsigned int> & mode1CC = { {-321,1},{ 211,1}, { 333,1}};
      static const map<PdgId,unsigned int> & mode2   = { { 310,1},{ 111,1}, { 333,1}};
      DecayedParticles B0 = apply<DecayedParticles>(event, "B0");
      // loop over particles
      for(unsigned int ix=0;ix<B0.decaying().size();++ix) {
        int sign = 1,imode=-1;
        if (B0.modeMatches(ix,3,mode1)) {
      imode = 0;
          sign  = 1;
    }
    else if(B0.modeMatches(ix,3,mode1CC)) {
      imode = 0;
          sign  =-1;
    }
    else if(B0.modeMatches(ix,3,mode2)) {
      imode = 1;
          sign  = 1;
    }
        else
          continue;
    // particles
        const Particle & KK  = B0.decayProducts()[ix].at(imode==0 ?  321*sign : 310)[0];
        const Particle & pi  = B0.decayProducts()[ix].at(imode==0 ? -211*sign : 111)[0];
    const Particle & phi = B0.decayProducts()[ix].at( 333     )[0];
    // children of the phi
    if(phi.children().size()!=2) continue;
    if(phi.children()[0].abspid()!=321) continue;
    if(phi.children()[0].pid()!=-phi.children()[1].pid()) continue;
    double mKpi = (KK.momentum()+pi.momentum()).mass();
    _h_mass[imode][0]->fill(mKpi);
    _h_mass[imode][1]->fill(phi.mass());
    Particle Kp1 = phi.children()[0];
    Particle Km1 = phi.children()[1];
    // B0 frame
    LorentzTransform boost1 = LorentzTransform::mkFrameTransformFromBeta(B0.decaying()[ix].momentum().betaVec());
    FourMomentum pKstar = boost1.transform(KK.momentum()+pi.momentum());
    FourMomentum pPhi   = boost1.transform(phi.momentum());
    // K pi helicity angle
    LorentzTransform boost2 = LorentzTransform::mkFrameTransformFromBeta(pKstar.betaVec());
    FourMomentum pKp = boost2.transform(boost1.transform(KK.momentum()));
    Vector3 axis1 = pKstar.p3().unit();
    double cTheta1 = axis1.dot(pKp.p3().unit());
    // phi helicity angle
    LorentzTransform boost3 = LorentzTransform::mkFrameTransformFromBeta(pPhi.betaVec());
    FourMomentum pKp1 = boost3.transform(boost1.transform(Kp1.momentum()));
    Vector3 axis2 = pPhi.p3().unit();
    double cTheta2 = axis2.dot(pKp1.p3().unit());
    if(mKpi>.75 && mKpi<1.05) {
      _h_angle[0][0]->fill(cTheta1);
      _h_angle[0][1]->fill(cTheta2);
      _p[0][0]->fill(-0.5*(1-5.*sqr(cTheta2)));
      _p[0][1]->fill();
    }
    else if(mKpi>1.13 && mKpi<1.53) {
      _h_angle[1][0]->fill(cTheta1);
      _h_angle[1][1]->fill(cTheta2);
      _p[1][0]->fill(-0.5*(1-5.*sqr(cTheta2)));
      _p[1][1]->fill();
    }
      }
    }


    /// Normalise histograms etc., after the run
    void finalize() {
      // histos
      for(unsigned int ix=0;ix<2;++ix) {
        scale(_p[ix][0], 1./ *_p[ix][1]);
    for(unsigned int iy=0;iy<2;++iy) {
      normalize(_h_mass[ix][iy] ,1.,false);
      normalize(_h_angle[ix][iy],1.,false);
    }
      }
    }

    /// @}


    /// @name Histograms
    /// @{
    Histo1DPtr _h_mass[2][2],_h_angle[2][2];
    CounterPtr _p[2][2];
    /// @}

  };


  RIVET_DECLARE_PLUGIN(BABAR_2008_I792439);

}