/home/bes3soft/bes3soft/Boss/7.0.2/dist/7.0.2/Generator/BesEvtGen/BesEvtGen-00-03-58/src/EvtGen/EvtGenBase/EvtSemiLeptonicVectorAmp.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: EvtSemiLeptonicVectorAmp.cc
//
// Description: Routine to implement semileptonic decays to vector
//              mesons. 
//
// Modification history:
//
//    DJL       April 17,1998       Module created
//
//------------------------------------------------------------------------
//
#include "EvtGenBase/EvtPatches.hh"
#include "EvtGenBase/EvtPatches.hh"
#include "EvtGenBase/EvtParticle.hh"
#include "EvtGenBase/EvtGenKine.hh"
#include "EvtGenBase/EvtPDL.hh"
#include "EvtGenBase/EvtReport.hh"
#include "EvtGenBase/EvtTensor4C.hh"
#include "EvtGenBase/EvtVector4C.hh"
#include "EvtGenBase/EvtDiracSpinor.hh"
#include "EvtGenBase/EvtSemiLeptonicVectorAmp.hh"
#include "EvtGenBase/EvtId.hh"
#include "EvtGenBase/EvtAmp.hh"
#include "EvtGenBase/EvtSemiLeptonicFF.hh"
using std::endl;

void EvtSemiLeptonicVectorAmp::CalcAmp( EvtParticle *parent,
                                        EvtAmp& amp,
                                        EvtSemiLeptonicFF *FormFactors ) {

  static EvtId EM=EvtPDL::getId("e-");
  static EvtId MUM=EvtPDL::getId("mu-");
  static EvtId TAUM=EvtPDL::getId("tau-");
  static EvtId EP=EvtPDL::getId("e+");
  static EvtId MUP=EvtPDL::getId("mu+");
  static EvtId TAUP=EvtPDL::getId("tau+");

  static EvtId D0=EvtPDL::getId("D0");
  static EvtId D0B=EvtPDL::getId("anti-D0");
  static EvtId DP=EvtPDL::getId("D+");
  static EvtId DM=EvtPDL::getId("D-");
  static EvtId DSM=EvtPDL::getId("D_s-");
  static EvtId DSP=EvtPDL::getId("D_s+");
  
  //Add the lepton and neutrino 4 momenta to find q2

  EvtVector4R q = parent->getDaug(1)->getP4() 
                    + parent->getDaug(2)->getP4(); 
  double q2 = (q.mass2());

  double a1f,a2f,vf,a0f,a3f;
  double m_meson = parent->getDaug(0)->mass();

  FormFactors->getvectorff(parent->getId(),
                           parent->getDaug(0)->getId(),
                           q2,
                           m_meson,
                           &a1f, 
                           &a2f, 
                           &vf, 
                           &a0f);

  double costhl_flag = 1.0;

  if(parent->getId()==D0||parent->getId()==D0B||
     parent->getId()==DP||parent->getId()==DM) {
    costhl_flag = -1.0;
  }
  if(parent->getId()==DSP||parent->getId()==DSM) {
    costhl_flag = -1.0;
  }
  vf = vf * costhl_flag;

  EvtVector4R p4b;
  p4b.set(parent->mass(),0.0,0.0,0.0);
 
  EvtVector4R p4meson = parent->getDaug(0)->getP4();

  EvtVector4C l1,l2;

  EvtId l_num = parent->getDaug(1)->getId();
  double m_b = parent->mass();

  a3f = ((m_b+m_meson)/(2.0*m_meson))*a1f -
        ((m_b-m_meson)/(2.0*m_meson))*a2f;

  EvtTensor4C tds;
  if (l_num==EM||l_num==MUM||l_num==TAUM){

    tds = a1f*(m_b+m_meson)*EvtTensor4C::g();
    //tds-=directProd((a2f/(m_b+m_meson))*p4b,p4b+p4meson);
    tds.addDirProd((-a2f/(m_b+m_meson))*p4b,p4b+p4meson);
    tds+=EvtComplex(0.0,vf/(m_b+m_meson))
                  *dual(directProd(p4meson+p4b,p4b-p4meson));
    //tds-=directProd((a3f-a0f)*2.0*(m_meson/q2)*p4b,p4b-p4meson);
    tds.addDirProd((a0f-a3f)*2.0*(m_meson/q2)*p4b,p4b-p4meson);

    l1=EvtLeptonVACurrent(parent->getDaug(1)->spParent(0),
                          parent->getDaug(2)->spParentNeutrino());
    l2=EvtLeptonVACurrent(parent->getDaug(1)->spParent(1),
                          parent->getDaug(2)->spParentNeutrino());
  }
  else{
    if (l_num==EP||l_num==MUP||l_num==TAUP){
    tds = a1f*(m_b+m_meson)*EvtTensor4C::g();
    //tds-=directProd((a2f/(m_b+m_meson))*p4b,p4b+p4meson);
    tds.addDirProd((-a2f/(m_b+m_meson))*p4b,p4b+p4meson);
    tds-=EvtComplex(0.0,vf/(m_b+m_meson))
                  *dual(directProd(p4meson+p4b,p4b-p4meson));
    //tds-=directProd((a3f-a0f)*2.0*(m_meson/q2)*p4b,p4b-p4meson);
    tds.addDirProd((a0f-a3f)*2.0*(m_meson/q2)*p4b,p4b-p4meson);

    l1=EvtLeptonVACurrent(parent->getDaug(2)->spParentNeutrino(),
                            parent->getDaug(1)->spParent(0));
    l2=EvtLeptonVACurrent(parent->getDaug(2)->spParentNeutrino(),
                            parent->getDaug(1)->spParent(1));
    }
    else{
      report(ERROR,"EvtGen") << "Wrong lepton number"<<endl;
    }
  }

  EvtVector4C et0=tds.cont1( parent->getDaug(0)->epsParent(0).conj() );
  EvtVector4C et1=tds.cont1( parent->getDaug(0)->epsParent(1).conj() );
  EvtVector4C et2=tds.cont1( parent->getDaug(0)->epsParent(2).conj() );


  amp.vertex(0,0,l1.cont(et0));
  amp.vertex(0,1,l2.cont(et0));

  amp.vertex(1,0,l1.cont(et1));
  amp.vertex(1,1,l2.cont(et1));

  amp.vertex(2,0,l1.cont(et2));
  amp.vertex(2,1,l2.cont(et2));

  return;
}

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