TEvtGen/EvtGenBase/EvtSemiLeptonicScalarAmp.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: EvtSemiLeptonicScalarAmp.cc
  12 //
  13 // Description: Routine to implement semileptonic decays to pseudo-scalar
  14 //              mesons.
  15 //
  16 // Modification history:
  17 //
  18 //    DJL       April 17,1998       Module created
  19 //
  20 //------------------------------------------------------------------------
  21 //
  22 #include "EvtGenBase/EvtPatches.hh"
  23 #include "EvtGenBase/EvtPatches.hh"
  24 #include "EvtGenBase/EvtParticle.hh"
  25 #include "EvtGenBase/EvtGenKine.hh"
  26 #include "EvtGenBase/EvtPDL.hh"
  27 #include "EvtGenBase/EvtReport.hh"
  28 #include "EvtGenBase/EvtVector4C.hh"
  29 #include "EvtGenBase/EvtTensor4C.hh"
  30 #include "EvtGenBase/EvtDiracSpinor.hh"
  31 #include "EvtGenBase/EvtSemiLeptonicScalarAmp.hh"
  32 #include "EvtGenBase/EvtId.hh"
  33 #include "EvtGenBase/EvtAmp.hh"
  34 #include "EvtGenBase/EvtSemiLeptonicFF.hh"
  35
  36 void EvtSemiLeptonicScalarAmp::CalcAmp( EvtParticle *parent,
  37                                         EvtAmp& amp,
  38                                         EvtSemiLeptonicFF *FormFactors ) {
  39
  40   static EvtId EM=EvtPDL::getId("e-");
  41   static EvtId MUM=EvtPDL::getId("mu-");
  42   static EvtId TAUM=EvtPDL::getId("tau-");
  43   static EvtId EP=EvtPDL::getId("e+");
  44   static EvtId MUP=EvtPDL::getId("mu+");
  45   static EvtId TAUP=EvtPDL::getId("tau+");
  46
  47   //Add the lepton and neutrino 4 momenta to find q2
  48
  49   EvtVector4R q = parent->getDaug(1)->getP4()
  50                     + parent->getDaug(2)->getP4();
  51   double q2 = (q.mass2());
  52
  53   double fpf,f0f;
  54   double mesonmass = parent->getDaug(0)->mass();
  55   double parentmass = parent->mass();
  56
  57   FormFactors->getscalarff(parent->getId(),
  58                            parent->getDaug(0)->getId(),
  59                            q2,
  60                            mesonmass,
  61                            &fpf,
  62                            &f0f);
  63
  64
  65   EvtVector4R p4b;
  66   p4b.set(parent->mass(),0.0,0.0,0.0);
  67   EvtVector4R p4meson = parent->getDaug(0)->getP4();
  68   double mdiffoverq2;
  69   mdiffoverq2 = parentmass*parentmass - mesonmass*mesonmass;
  70   mdiffoverq2 = mdiffoverq2 / q2;
  71
  72   EvtVector4C l1,l2;
  73
  74   EvtId l_num = parent->getDaug(1)->getId();
  75   EvtVector4C tds;
  76
  77   if (l_num==EM||l_num==MUM||l_num==TAUM){
  78
  79     tds = EvtVector4C(fpf*(p4b+p4meson - (mdiffoverq2*(p4b-p4meson)))+
  80                     + f0f*mdiffoverq2*(p4b-p4meson));
  81
  82     l1=EvtLeptonVACurrent(parent->getDaug(1)->spParent(0),
  83                           parent->getDaug(2)->spParentNeutrino());
  84     l2=EvtLeptonVACurrent(parent->getDaug(1)->spParent(1),
  85                           parent->getDaug(2)->spParentNeutrino());
  86   }
  87   else{
  88     if (l_num==EP||l_num==MUP||l_num==TAUP){
  89
  90       tds = EvtVector4C(fpf*(p4b+p4meson - (mdiffoverq2*(p4b-p4meson)))+
  91                     + f0f*mdiffoverq2*(p4b-p4meson));
  92
  93       l1=EvtLeptonVACurrent(parent->getDaug(2)->spParentNeutrino(),
  94                             parent->getDaug(1)->spParent(0));
  95       l2=EvtLeptonVACurrent(parent->getDaug(2)->spParentNeutrino(),
  96                             parent->getDaug(1)->spParent(1));
  97     }
  98     else{
  99       report(ERROR,"EvtGen") << "dfnb89agngri wrong lepton number\n";
 100     }
 101   }
 102
 103   amp.vertex(0,l1*tds);
 104   amp.vertex(1,l2*tds);
 105
 106 }
 107