TEvtGen/EvtGenBase/EvtRaritaSchwingerParticle.cpp

   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: EvtRaritaSchwingerParticle.cc
  12 //
  13 // Description: Class to describe spin 1/2 particles.
  14 //
  15 // Modification history:
  16 //
  17 //   RYD     August 9, 2000         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/EvtRaritaSchwingerParticle.hh"
  27 #include "EvtGenBase/EvtDiracSpinor.hh"
  28 #include "EvtGenBase/EvtVector4R.hh"
  29 #include "EvtGenBase/EvtPDL.hh"
  30 #include "EvtGenBase/EvtReport.hh"
  31 using std::endl;
  32
  33 EvtRaritaSchwingerParticle::~EvtRaritaSchwingerParticle(){}
  34
  35
  36 EvtRaritaSchwingerParticle::EvtRaritaSchwingerParticle(){
  37
  38   return;
  39
  40 }
  41
  42 void EvtRaritaSchwingerParticle::init(EvtId id,const EvtVector4R& p4){
  43
  44     _validP4=true;
  45     setp(p4);
  46     setpart_num(id);
  47
  48     if (EvtPDL::getStdHep(id)==0){
  49         report(ERROR,"EvtGen") << "Error in EvtRaritaSchwingerParticle::init, part_n="
  50                                << id.getId()<<endl;
  51         ::abort();
  52     }
  53
  54
  55
  56     double sqmt2=sqrt(2.0*(this->getP4().mass()));
  57
  58     EvtDiracSpinor spplus;
  59     EvtDiracSpinor spminus;
  60
  61     if (EvtPDL::getStdHep(getId())>0){
  62         spplus.set(sqmt2,0.0,0.0,0.0);
  63         spminus.set(0.0,sqmt2,0.0,0.0);
  64     } else {
  65         spplus.set(0.0,0.0,sqmt2,0.0);
  66         spminus.set(0.0,0.0,0.0,sqmt2);
  67     }
  68
  69     static EvtVector4C eplus(0.0,-1.0/sqrt(2.0),EvtComplex(0.0,-1.0/sqrt(2.0)),0.0);
  70     static EvtVector4C ezero(0.0,0.0,0.0,1.0);
  71     static EvtVector4C eminus(0.0,1.0/sqrt(2.0),EvtComplex(0.0,-1.0/sqrt(2.0)),0.0);
  72
  73     _spinorRest[0]=dirProd(eplus,spplus);
  74     _spinorRest[1]=dirProd(sqrt(2.0/3.0)*ezero,spplus)+
  75         dirProd(sqrt(1.0/3.0)*eplus,spminus);
  76     _spinorRest[2]=dirProd(sqrt(2.0/3.0)*ezero,spminus)+
  77         dirProd(sqrt(1.0/3.0)*eminus,spplus);
  78     _spinorRest[3]=dirProd(eminus,spminus);
  79
  80     _spinor[0]=boostTo(_spinorRest[0],p4);
  81     _spinor[1]=boostTo(_spinorRest[1],p4);
  82     _spinor[2]=boostTo(_spinorRest[2],p4);
  83     _spinor[3]=boostTo(_spinorRest[3],p4);
  84
  85
  86     setLifetime();
  87 }
  88
  89
  90 void EvtRaritaSchwingerParticle::init(EvtId id,const EvtVector4R& p4,
  91                                       const EvtRaritaSchwinger & prod1,
  92                                       const EvtRaritaSchwinger & prod2,
  93                                       const EvtRaritaSchwinger & prod3,
  94                                       const EvtRaritaSchwinger & prod4,
  95                                       const EvtRaritaSchwinger & rest1,
  96                                       const EvtRaritaSchwinger & rest2,
  97                                       const EvtRaritaSchwinger & rest3,
  98                                       const EvtRaritaSchwinger & rest4){
  99
 100   _validP4=true;
 101   setp(p4);
 102   setpart_num(id);
 103
 104   if (EvtPDL::getStdHep(id)==0){
 105     report(ERROR,"EvtGen") << "Error in EvtRaritaSchwingerParticle::init, part_n="
 106                            << id.getId()<<std::endl;
 107     ::abort();
 108   }
 109   _spinorRest[0]=rest1;
 110   _spinorRest[1]=rest2;
 111   _spinorRest[2]=rest3;
 112   _spinorRest[3]=rest4;
 113
 114   _spinor[0]=prod1;
 115   _spinor[1]=prod2;
 116   _spinor[2]=prod3;
 117   _spinor[3]=prod4;
 118
 119   setLifetime();
 120 }
 121
 122
 123
 124 EvtRaritaSchwinger EvtRaritaSchwingerParticle::spRSParent(int i) const {
 125
 126   return _spinor[i];
 127
 128 }
 129
 130 EvtRaritaSchwinger EvtRaritaSchwingerParticle::spRS(int i) const {
 131
 132   return _spinorRest[i];
 133
 134 }
 135
 136
 137
 138 EvtSpinDensity EvtRaritaSchwingerParticle::rotateToHelicityBasis() const{
 139
 140   double sqmt2=sqrt(2.0*(this->getP4().mass()));
 141
 142   EvtDiracSpinor spplus;
 143   EvtDiracSpinor spminus;
 144
 145   if (EvtPDL::getStdHep(getId())>0){
 146     spplus.set(1.0,0.0,0.0,0.0);
 147     spminus.set(0.0,1.0,0.0,0.0);
 148   } else {
 149     spplus.set(0.0,0.0,1.0,0.0);
 150     spminus.set(0.0,0.0,0.0,1.0);
 151   }
 152
 153   EvtVector4C eplus(0.0,-1.0/sqrt(2.0),EvtComplex(0.0,-1.0/sqrt(2.0)),0.0);
 154   EvtVector4C ezero(0.0,0.0,0.0,1.0);
 155   EvtVector4C eminus(0.0,1.0/sqrt(2.0),EvtComplex(0.0,-1.0/sqrt(2.0)),0.0);
 156
 157   EvtRaritaSchwinger sppp=dirProd(eplus,spplus);
 158   EvtRaritaSchwinger spp=dirProd(sqrt(2.0/3.0)*ezero,spplus)+
 159     dirProd(sqrt(1.0/3.0)*eplus,spminus);
 160   EvtRaritaSchwinger spm=dirProd(sqrt(2.0/3.0)*ezero,spminus)+
 161     dirProd(sqrt(1.0/3.0)*eminus,spplus);
 162   EvtRaritaSchwinger spmm=dirProd(eminus,spminus);
 163
 164
 165   EvtSpinDensity R;
 166   R.setDim(4);
 167
 168
 169   for ( int i=0; i<4; i++) {
 170     R.set(0,i,(sppp*_spinorRest[i])/sqmt2);
 171     R.set(1,i,(spp*_spinorRest[i])/sqmt2);
 172     R.set(2,i,(spm*_spinorRest[i])/sqmt2);
 173     R.set(3,i,(spmm*_spinorRest[i])/sqmt2);
 174   }
 175
 176   return R;
 177
 178 }
 179
 180
 181 EvtSpinDensity EvtRaritaSchwingerParticle::rotateToHelicityBasis(double alpha,
 182                                                                  double beta,
 183                                                                  double gamma) const{
 184
 185   EvtDiracSpinor spplus;
 186   EvtDiracSpinor spminus;
 187
 188   if (EvtPDL::getStdHep(getId())>0){
 189     spplus.set(1.0,0.0,0.0,0.0);
 190     spminus.set(0.0,1.0,0.0,0.0);
 191   } else {
 192     spplus.set(0.0,0.0,1.0,0.0);
 193     spminus.set(0.0,0.0,0.0,1.0);
 194   }
 195
 196   EvtVector4C eplus(0.0,-1.0/sqrt(2.0),EvtComplex(0.0,-1.0/sqrt(2.0)),0.0);
 197   EvtVector4C ezero(0.0,0.0,0.0,1.0);
 198   EvtVector4C eminus(0.0,1.0/sqrt(2.0),EvtComplex(0.0,-1.0/sqrt(2.0)),0.0);
 199
 200   EvtRaritaSchwinger sppp=dirProd(eplus,spplus);
 201   EvtRaritaSchwinger spp=dirProd(sqrt(2.0/3.0)*ezero,spplus)+
 202     dirProd(sqrt(1.0/3.0)*eplus,spminus);
 203   EvtRaritaSchwinger spm=dirProd(sqrt(2.0/3.0)*ezero,spminus)+
 204     dirProd(sqrt(1.0/3.0)*eminus,spplus);
 205   EvtRaritaSchwinger spmm=dirProd(eminus,spminus);
 206
 207
 208   sppp.applyRotateEuler(alpha,beta,gamma);
 209   spp.applyRotateEuler(alpha,beta,gamma);
 210   spm.applyRotateEuler(alpha,beta,gamma);
 211   spmm.applyRotateEuler(alpha,beta,gamma);
 212
 213   EvtSpinDensity R;
 214   R.setDim(4);
 215
 216   double sqmt2=sqrt(2.0*(this->getP4().mass()));
 217
 218   for ( int i=0; i<4; i++) {
 219     R.set(0,i,(sppp*_spinorRest[i])/sqmt2);
 220     R.set(1,i,(spp*_spinorRest[i])/sqmt2);
 221     R.set(2,i,(spm*_spinorRest[i])/sqmt2);
 222     R.set(3,i,(spmm*_spinorRest[i])/sqmt2);
 223   }
 224
 225   return R;
 226
 227 }
 228