1// -*- C++ -*-
  2#include "Rivet/Analysis.hh"
  3#include "Rivet/Projections/UnstableParticles.hh"
  4#include "Rivet/Projections/DecayedParticles.hh"
  5
  6namespace Rivet {
  7
  8
  9  /// @brief  B -> omega K
 10  class BABAR_2007_I754030 : public Analysis {
 11  public:
 12
 13    /// Constructor
 14    RIVET_DEFAULT_ANALYSIS_CTOR(BABAR_2007_I754030);
 15
 16
 17    /// @name Analysis methods
 18    /// @{
 19
 20    /// Book histograms and initialise projections before the run
 21    void init() {
 22      // Initialise and register projections
 23      UnstableParticles ufs = UnstableParticles(Cuts::abspid==521);
 24      declare(ufs, "UFS");
 25      DecayedParticles BP(ufs);
 26      BP.addStable(310);
 27      BP.addStable(223);
 28      declare(BP, "BP");
 29      // histos
 30      book(_h,1,1,1);
 31    }
 32
 33    void findChildren(const Particle & p, Particles & pim, Particles & pip,
 34		      Particles & pi0, unsigned int &ncount) {
 35      for( const Particle &child : p.children()) {
 36	if(child.pid()==PID::PIPLUS) {
 37	  pip.push_back(child);
 38	  ncount+=1;
 39	}
 40	else if(child.pid()==PID::PIMINUS) {
 41	  pim.push_back(child);
 42	  ncount+=1;
 43	}
 44	else if(child.pid()==PID::PI0) {
 45	  pi0.push_back(child);
 46	  ncount+=1;
 47	}
 48	else if(child.children().empty()) {
 49	  ncount+=1;
 50	}
 51    	else
 52    	  findChildren(child,pim,pip,pi0,ncount);
 53      }
 54    }
 55
 56    /// Perform the per-event analysis
 57    void analyze(const Event& event) {
 58      static const map<PdgId,unsigned int> & mode   = { { 223,1}, { 321,1}};
 59      static const map<PdgId,unsigned int> & modeCC = { { 223,1}, {-321,1}};
 60      DecayedParticles BP = apply<DecayedParticles>(event, "BP");
 61      // loop over particles
 62      for(unsigned int ix=0;ix<BP.decaying().size();++ix) {
 63	if (BP.modeMatches(ix,2,mode) || BP.modeMatches(ix,2,modeCC)) {
 64	  const Particle & omega = BP.decayProducts()[ix].at(223)[0];
 65	  // children of the omega
 66	  unsigned int ncount=0;
 67	  Particles pip,pim,pi0;
 68	  findChildren(omega,pim,pip,pi0,ncount);
 69	  if( ncount!=3 || !(pim.size()==1 && pip.size()==1 && pi0.size()==1)) continue;
 70	  LorentzTransform boost1 = LorentzTransform::mkFrameTransformFromBeta(BP.decaying()[ix].momentum().betaVec());
 71	  FourMomentum pomega = boost1.transform(omega.momentum());
 72	  FourMomentum pPip   = boost1.transform(pip[0].momentum());
 73	  FourMomentum pPim   = boost1.transform(pim[0].momentum());
 74	  // boost to omega frame
 75	  LorentzTransform boost3 = LorentzTransform::mkFrameTransformFromBeta(pomega.betaVec());
 76	  pPip   = boost3.transform(pPip);
 77	  pPim   = boost3.transform(pPim);
 78	  Vector3 axisOmega = pPip.p3().cross(pPim.p3()).unit();
 79	  // helicity angle
 80	  _h->fill(abs(pomega.p3().unit().dot(axisOmega)));
 81	}
 82      }
 83    }
 84
 85
 86    /// Normalise histograms etc., after the run
 87    void finalize() {
 88      normalize(_h,1.,false);
 89    }
 90
 91    /// @}
 92
 93
 94    /// @name Histograms
 95    /// @{
 96    Histo1DPtr _h;
 97    /// @}
 98
 99
100  };
101
102
103  RIVET_DECLARE_PLUGIN(BABAR_2007_I754030);
104
105}