BesEvtGen-00-04-08/src/EvtGen/EvtGenBase/EvtEvalHelAmp.hh

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//--------------------------------------------------------------------------
//
// Environment:
//      This software is part of the EvtGen package developed jointly
//      for the BaBar and CLEO collaborations.  If you use all or part
//      of it, please give an appropriate acknowledgement.
//
// Copyright Information: See EvtGen/COPYRIGHT
//      Copyright (C) 2002      Caltech
//
// Module: EvtGen/EvtEvalHelAmp.hh
//
// Description: Class for evaluation of amplitudes in the 
//              helicity formalism.
//             
//
// Modification history:
//
//    RYD      October 24, 2002         Module created
//
//------------------------------------------------------------------------
 
#ifndef EVTEVALHELAMP_HH
#define EVTEVALHELAMP_HH
 
#include "EvtGenBase/EvtDecayAmp.hh"
#include "EvtGenBase/EvtSpinType.hh"
#include "EvtGenBase/EvtId.hh"
 
class EvtParticle;
class EvtAmp;
 
class EvtEvalHelAmp{
 
public:
 
  EvtEvalHelAmp(EvtSpinType::spintype A,
        EvtSpinType::spintype B,
        EvtSpinType::spintype C,
        EvtComplexPtrPtr HBC);
 
  virtual ~EvtEvalHelAmp();
 
  double probMax();
 
  void evalAmp(EvtParticle *p, EvtAmp& amp); 
 
 
private:
 
  void fillHelicity(int* lambda2,int n,int J2);
  void setUpRotationMatrices(EvtParticle *p,double theta, double phi);
  void applyRotationMatrices();
 
  //spins states available for particle A, B, and C.
  int _nA,_nB,_nC;
 
  //helicity amplitudes
  EvtComplexPtrPtr _HBC;
 
  //2 times spin for each of the particles
  int _JA2,_JB2,_JC2;
 
  //2 times the helicity for the states
  int *_lambdaA2,*_lambdaB2,*_lambdaC2;
 
  //Rotation matrices
  EvtComplexPtrPtr _RA,_RB,_RC;
 
  //temporary array for amplitudes
  EvtComplexPtrPtrPtr _amp,_amp1,_amp3;
 
};
 
#endif