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 "EvtSemiLeptonicVectorAmp.hh"
#include "EvtAmp.hh"
#include "EvtDiracSpinor.hh"
#include "EvtGenKine.hh"
#include "EvtId.hh"
#include "EvtPDL.hh"
#include "EvtParticle.hh"
#include "EvtPatches.hh"
#include "EvtReport.hh"
#include "EvtSemiLeptonicFF.hh"
#include "EvtTensor4C.hh"
#include "EvtVector4C.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;
}