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 rho+ 
 10  class BABAR_2005_I664717 : public Analysis {
 11  public:
 12
 13    /// Constructor
 14    RIVET_DEFAULT_ANALYSIS_CTOR(BABAR_2005_I664717);
 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( 213);
 27      BP.addStable(-213);
 28      BP.addStable( 223);
 29      declare(BP, "BP");
 30      // histos
 31      for(unsigned int ix=0;ix<2;++ix)
 32	book(_h[ix],1,1,1+ix);
 33    }
 34
 35    void findChildren(const Particle & p, Particles & pim, Particles & pip,
 36		      Particles & pi0, unsigned int &ncount) {
 37      for( const Particle &child : p.children()) {
 38	if(child.pid()==PID::PIPLUS) {
 39	  pip.push_back(child);
 40	  ncount+=1;
 41	}
 42	else if(child.pid()==PID::PIMINUS) {
 43	  pim.push_back(child);
 44	  ncount+=1;
 45	}
 46	else if(child.pid()==PID::PI0) {
 47	  pi0.push_back(child);
 48	  ncount+=1;
 49	}
 50	else if(child.children().empty()) {
 51	  ncount+=1;
 52	}
 53    	else
 54    	  findChildren(child,pim,pip,pi0,ncount);
 55      }
 56    }
 57
 58    /// Perform the per-event analysis
 59    void analyze(const Event& event) {
 60      static const map<PdgId,unsigned int> & mode   = { { 223,1}, { 213,1}};
 61      static const map<PdgId,unsigned int> & modeCC = { { 223,1}, {-213,1}};
 62      DecayedParticles BP = apply<DecayedParticles>(event, "BP");
 63      // loop over particles
 64      for(unsigned int ix=0;ix<BP.decaying().size();++ix) {
 65      	if (BP.modeMatches(ix,2,mode) || BP.modeMatches(ix,2,modeCC)) {
 66	  const Particle & omega = BP.decayProducts()[ix].at(223)[0];
 67	  // children of the omega
 68	  unsigned int ncount=0;
 69	  Particles pip,pim,pi0;
 70	  findChildren(omega,pim,pip,pi0,ncount);
 71	  if( ncount!=3 || !(pim.size()==1 && pip.size()==1 && pi0.size()==1)) continue;
 72	  // rho decay
 73	  int sign = BP.decaying()[ix].pid()/BP.decaying()[ix].abspid();
 74	  const Particle & rho = BP.decayProducts()[ix].at(sign*213)[0];
 75	  if(rho.children().size()!=2) continue;
 76	  Particle pi;
 77	  if(rho.children()[0].pid()==sign*211 &&
 78	     rho.children()[1].pid()==111)
 79	    pi = rho.children()[0];
 80	  else if (rho.children()[1].pid()==sign*211 &&
 81		   rho.children()[0].pid()==111)
 82	    pi = rho.children()[1];
 83	  else continue;
 84	  // boosts
 85	  LorentzTransform boost1 = LorentzTransform::mkFrameTransformFromBeta(BP.decaying()[ix].momentum().betaVec());
 86	  FourMomentum pomega = boost1.transform(omega .momentum());
 87	  FourMomentum prho   = boost1.transform(  rho .momentum());
 88	  FourMomentum pPip   = boost1.transform(pip[0].momentum());
 89	  FourMomentum pPim   = boost1.transform(pim[0].momentum());
 90	  FourMomentum pPi    = boost1.transform(pi    .momentum());
 91	  // boost to omega frame
 92	  LorentzTransform boost2 = LorentzTransform::mkFrameTransformFromBeta(pomega.betaVec());
 93	  pPip   = boost2.transform(pPip);
 94	  pPim   = boost2.transform(pPim);
 95	  Vector3 axisOmega = pPip.p3().cross(pPim.p3()).unit();
 96	  // helicity angle
 97	  _h[0]->fill(abs(pomega.p3().unit().dot(axisOmega)));
 98	  // boost to rho rest frame
 99	  LorentzTransform boost3 = LorentzTransform::mkFrameTransformFromBeta(prho.betaVec());
100	  pPi = boost3.transform(pPi);
101	  _h[1]->fill(prho.p3().unit().dot(pPi.p3().unit()));
102      	}
103      }
104    }
105
106
107    /// Normalise histograms etc., after the run
108    void finalize() {
109      for(unsigned int ix=0;ix<2;++ix)
110	normalize(_h[ix],1.,false);
111    }
112
113    /// @}
114
115
116    /// @name Histograms
117    /// @{
118    Histo1DPtr _h[2];
119    /// @}
120
121
122  };
123
124
125  RIVET_DECLARE_PLUGIN(BABAR_2005_I664717);
126
127}