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 "EvtDecayAmp.hh"
#include "EvtId.hh"
#include "EvtSpinType.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