TEvtGen/EvtGenBase/EvtVectorParticle.cxx

   1 //--------------------------------------------------------------------------
   2 //
   3 // Environment:
   4 //      This software is part of the EvtGen package developed jointly
   5 //      for the BaBar and CLEO collaborations.  If you use all or part
   6 //      of it, please give an appropriate acknowledgement.
   7 //
   8 // Copyright Information: See EvtGen/COPYRIGHT
   9 //      Copyright (C) 1998      Caltech, UCSB
  10 //
  11 // Module: EvtVectorParticle.cc
  12 //
  13 // Description: Class to describe spin 1 particles
  14 //
  15 // Modification history:
  16 //
  17 //    DJL/RYD   September 25, 1996           Module created
  18 //
  19 //------------------------------------------------------------------------
  20 //
  21 #include "EvtGenBase/EvtPatches.hh"
  22 #include <stdlib.h>
  23 #include <iostream>
  24 #include <math.h>
  25 #include "EvtGenBase/EvtComplex.hh"
  26 #include "EvtGenBase/EvtVectorParticle.hh"
  27 #include "EvtGenBase/EvtVector4C.hh"
  28 #include "EvtGenBase/EvtPDL.hh"
  29 #include "EvtGenBase/EvtReport.hh"
  30
  31 EvtVectorParticle::~EvtVectorParticle(){}
  32
  33
  34 void EvtVectorParticle::init(EvtId part_n,double e,double px,double py,double pz){
  35
  36   _validP4=true;
  37   setp(e,px,py,pz);
  38   setpart_num(part_n);
  39
  40   _eps[0].set(0.0,1.0,0.0,0.0);
  41   _eps[1].set(0.0,0.0,1.0,0.0);
  42   _eps[2].set(0.0,0.0,0.0,1.0);
  43
  44   setLifetime();
  45 }
  46
  47 void EvtVectorParticle::init(EvtId part_n,const EvtVector4R& p4){
  48
  49   _validP4=true;
  50   setp(p4);
  51   setpart_num(part_n);
  52
  53   _eps[0].set(0.0,1.0,0.0,0.0);
  54   _eps[1].set(0.0,0.0,1.0,0.0);
  55   _eps[2].set(0.0,0.0,0.0,1.0);
  56   setLifetime();
  57 }
  58
  59 void EvtVectorParticle::init(EvtId part_n,const EvtVector4R& p4,
  60                              const EvtVector4C & epsin1,
  61                              const EvtVector4C & epsin2,
  62                              const EvtVector4C & epsin3){
  63
  64   _validP4=true;
  65   setp(p4);
  66   setpart_num(part_n);
  67
  68   _eps[0]=epsin1;
  69   _eps[1]=epsin2;
  70   _eps[2]=epsin3;
  71
  72   setLifetime();
  73 }
  74
  75
  76
  77 EvtSpinDensity EvtVectorParticle::rotateToHelicityBasis() const{
  78
  79   static EvtVector4C eplus(0.0,-1.0/sqrt(2.0),EvtComplex(0.0,-1.0/sqrt(2.0)),0.0);
  80   static EvtVector4C ezero(0.0,0.0,0.0,1.0);
  81   static EvtVector4C eminus(0.0,1.0/sqrt(2.0),EvtComplex(0.0,-1.0/sqrt(2.0)),0.0);
  82
  83   static EvtVector4C eplusC(eplus.conj());
  84   static EvtVector4C ezeroC(ezero.conj());
  85   static EvtVector4C eminusC(eminus.conj());
  86
  87   EvtSpinDensity R;
  88   R.setDim(3);
  89
  90   for ( int i=0; i<3; i++ ) {
  91     R.set(0,i,(eplusC)*_eps[i]);
  92     R.set(1,i,(ezeroC)*_eps[i]);
  93     R.set(2,i,(eminusC)*_eps[i]);
  94   }
  95
  96   return R;
  97
  98 }
  99
 100
 101 EvtSpinDensity EvtVectorParticle::rotateToHelicityBasis(double alpha,
 102                                                         double beta,
 103                                                         double gamma) const{
 104
 105   EvtVector4C eplus(0.0,-1.0/sqrt(2.0),EvtComplex(0.0,-1.0/sqrt(2.0)),0.0);
 106   EvtVector4C ezero(0.0,0.0,0.0,1.0);
 107   EvtVector4C eminus(0.0,1.0/sqrt(2.0),EvtComplex(0.0,-1.0/sqrt(2.0)),0.0);
 108
 109   eplus.applyRotateEuler(alpha,beta,gamma);
 110   ezero.applyRotateEuler(alpha,beta,gamma);
 111   eminus.applyRotateEuler(alpha,beta,gamma);
 112
 113   EvtSpinDensity R;
 114   R.setDim(3);
 115
 116
 117   for ( int i=0; i<3; i++ ) {
 118     R.set(0,i,(eplus.conj())*_eps[i]);
 119     R.set(1,i,(ezero.conj())*_eps[i]);
 120     R.set(2,i,(eminus.conj())*_eps[i]);
 121   }
 122
 123   return R;
 124
 125 }
 126
 127