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 B0 -> phi K* 
 10  class BELLE_2013_I1247059 : public Analysis {
 11  public:
 12
 13    /// Constructor
 14    RIVET_DEFAULT_ANALYSIS_CTOR(BELLE_2013_I1247059);
 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==511);
 24      declare(ufs, "UFS");
 25      DecayedParticles B0(ufs);
 26      B0.addStable(333);
 27      declare(B0, "B0");
 28      // histograms
 29      for(unsigned int ix=0;ix<4;++ix)
 30	book(_h[ix],1,1,1+ix);
 31    }
 32
 33
 34    /// Perform the per-event analysis
 35    void analyze(const Event& event) {
 36      static const map<PdgId,unsigned int> & mode   = { { 321,1},{-211,1}, { 333,1}};
 37      static const map<PdgId,unsigned int> & modeCC = { {-321,1},{ 211,1}, { 333,1}};
 38      DecayedParticles B0 = apply<DecayedParticles>(event, "B0");
 39      // loop over particles
 40      for(unsigned int ix=0;ix<B0.decaying().size();++ix) {
 41      	int sign = 1;
 42      	if (B0.decaying()[ix].pid()>0 && B0.modeMatches(ix,3,mode)) {
 43      	  sign=1;
 44      	}
 45      	else if  (B0.decaying()[ix].pid()<0 && B0.modeMatches(ix,3,modeCC)) {
 46      	  sign=-1;
 47      	}
 48      	else
 49      	  continue;
 50      	const Particle & Kp  = B0.decayProducts()[ix].at( 321*sign)[0];
 51      	const Particle & pim = B0.decayProducts()[ix].at(-211*sign)[0];
 52	const Particle & phi = B0.decayProducts()[ix].at( 333     )[0];
 53	if(phi.children().size()!=2 || phi.children()[0].pid()!=-phi.children()[1].pid() ||
 54	   phi.children()[0].abspid()!=321) continue;
 55	Particle Kp1 = phi.children()[0];
 56	Particle Km1 = phi.children()[1];
 57	if(Kp1.pid()<0) swap(Kp1,Km1);
 58	// B0 frame
 59	LorentzTransform boost1 = LorentzTransform::mkFrameTransformFromBeta(B0.decaying()[ix].momentum().betaVec());
 60	FourMomentum pKstar = boost1.transform(Kp.momentum()+pim.momentum());
 61	FourMomentum pPhi   = boost1.transform(phi.momentum());
 62	// stuff in K* frame
 63	LorentzTransform boost2 = LorentzTransform::mkFrameTransformFromBeta(pKstar.betaVec());
 64	FourMomentum pKp = boost2.transform(boost1.transform(Kp.momentum()));
 65	Vector3 axis1 = pKstar.p3().unit();
 66	double cTheta1 = axis1.dot(pKp.p3().unit());
 67	if(cTheta1>0.75) continue;
 68	Vector3 trans1 = pKp.p3() - cTheta1*pKp.p3().mod()*axis1;
 69	// stuff in phi frame
 70	LorentzTransform boost3 = LorentzTransform::mkFrameTransformFromBeta(pPhi.betaVec());
 71	FourMomentum pKp1 = boost3.transform(boost1.transform(Kp1.momentum()));
 72	Vector3 axis2 = pPhi.p3().unit();
 73	double cTheta2 = axis2.dot(pKp1.p3().unit());
 74	Vector3 trans2 = pKp1.p3() - cTheta2*pKp1.p3().mod()*axis2;
 75	// angle between planes
 76	double chi = atan2(trans1.cross(trans2).dot(axis1),trans1.dot(trans2));
 77	// fill histos
 78	_h[0]->fill(pKstar.mass());
 79	_h[1]->fill(cTheta1);
 80	_h[2]->fill(cTheta2);
 81	_h[3]->fill(chi);
 82      }
 83    }
 84
 85
 86    /// Normalise histograms etc., after the run
 87    void finalize() {
 88      for(unsigned int ix=0;ix<4;++ix)
 89	normalize(_h[ix],1.,false);
 90    }
 91
 92    /// @}
 93
 94
 95    /// @name Histograms
 96    /// @{
 97    Histo1DPtr _h[4];
 98    /// @}
 99
100
101  };
102
103
104  RIVET_DECLARE_PLUGIN(BELLE_2013_I1247059);
105
106}