EvtVectorParticle.cc

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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) 1998      Caltech, UCSB
//
// Module: EvtVectorParticle.cc
//
// Description: Class to describe spin 1 particles
//
// Modification history:
//
//    DJL/RYD   September 25, 1996           Module created
//
//------------------------------------------------------------------------
//
#include "EvtVectorParticle.hh"
#include "EvtComplex.hh"
#include "EvtPDL.hh"
#include "EvtPatches.hh"
#include "EvtReport.hh"
#include "EvtVector4C.hh"
#include <iostream>
#include <math.h>
#include <stdlib.h>
 
EvtVectorParticle::~EvtVectorParticle() {}
 
void EvtVectorParticle::init( EvtId part_n, double e, double px, double py, double pz ) {
 
  _validP4 = true;
  setp( e, px, py, pz );
  setpart_num( part_n );
 
  _eps[0].set( 0.0, 1.0, 0.0, 0.0 );
  _eps[1].set( 0.0, 0.0, 1.0, 0.0 );
  _eps[2].set( 0.0, 0.0, 0.0, 1.0 );
 
  setLifetime();
}
 
void EvtVectorParticle::init( EvtId part_n, const EvtVector4R& p4 ) {
 
  _validP4 = true;
  setp( p4 );
  setpart_num( part_n );
 
  _eps[0].set( 0.0, 1.0, 0.0, 0.0 );
  _eps[1].set( 0.0, 0.0, 1.0, 0.0 );
  _eps[2].set( 0.0, 0.0, 0.0, 1.0 );
 
  setLifetime();
}
 
EvtSpinDensity EvtVectorParticle::rotateToHelicityBasis() const {
 
  static EvtVector4C eplus( 0.0, -1.0 / sqrt( 2.0 ), EvtComplex( 0.0, -1.0 / sqrt( 2.0 ) ),
                            0.0 );
  static EvtVector4C ezero( 0.0, 0.0, 0.0, 1.0 );
  static EvtVector4C eminus( 0.0, 1.0 / sqrt( 2.0 ), EvtComplex( 0.0, -1.0 / sqrt( 2.0 ) ),
                             0.0 );
 
  static EvtVector4C eplusC( eplus.conj() );
  static EvtVector4C ezeroC( ezero.conj() );
  static EvtVector4C eminusC( eminus.conj() );
 
  EvtSpinDensity R;
  R.SetDim( 3 );
 
  for ( int i = 0; i < 3; i++ )
  {
    R.Set( 0, i, (eplusC)*_eps[i] );
    R.Set( 1, i, (ezeroC)*_eps[i] );
    R.Set( 2, i, (eminusC)*_eps[i] );
  }
 
  return R;
}
 
EvtSpinDensity EvtVectorParticle::rotateToHelicityBasis( double alpha, double beta,
                                                         double gamma ) const {
 
  EvtVector4C eplus( 0.0, -1.0 / sqrt( 2.0 ), EvtComplex( 0.0, -1.0 / sqrt( 2.0 ) ), 0.0 );
  EvtVector4C ezero( 0.0, 0.0, 0.0, 1.0 );
  EvtVector4C eminus( 0.0, 1.0 / sqrt( 2.0 ), EvtComplex( 0.0, -1.0 / sqrt( 2.0 ) ), 0.0 );
 
  eplus.applyRotateEuler( alpha, beta, gamma );
  ezero.applyRotateEuler( alpha, beta, gamma );
  eminus.applyRotateEuler( alpha, beta, gamma );
 
  EvtSpinDensity R;
  R.SetDim( 3 );
 
  for ( int i = 0; i < 3; i++ )
  {
    R.Set( 0, i, ( eplus.conj() ) * _eps[i] );
    R.Set( 1, i, ( ezero.conj() ) * _eps[i] );
    R.Set( 2, i, ( eminus.conj() ) * _eps[i] );
  }
 
  return R;
}