EvtSemiLeptonicTensorAmp.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: EvtSemiLeptonicTensorAmp.cc
//
// Description: Routine to implement semileptonic decays to pseudo-scalar
//              mesons.
//
// Modification history:
//
//    DJL       April 17,1998       Module created
//
//------------------------------------------------------------------------
//
#include "EvtSemiLeptonicTensorAmp.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"
 
void EvtSemiLeptonicTensorAmp::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 hf, kf, bpf, bmf;
 
  FormFactors->gettensorff( parent->getId(), parent->getDaug( 0 )->getId(), q2,
                            parent->getDaug( 0 )->mass(), &hf, &kf, &bpf, &bmf );
 
  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; }
  hf = hf * 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();
 
  EvtVector4C ep_meson_b[5];
 
  ep_meson_b[0] = ( ( parent->getDaug( 0 )->epsTensorParent( 0 ) ).cont2( p4b ) ).conj();
  ep_meson_b[1] = ( ( parent->getDaug( 0 )->epsTensorParent( 1 ) ).cont2( p4b ) ).conj();
  ep_meson_b[2] = ( ( parent->getDaug( 0 )->epsTensorParent( 2 ) ).cont2( p4b ) ).conj();
  ep_meson_b[3] = ( ( parent->getDaug( 0 )->epsTensorParent( 3 ) ).cont2( p4b ) ).conj();
  ep_meson_b[4] = ( ( parent->getDaug( 0 )->epsTensorParent( 4 ) ).cont2( p4b ) ).conj();
 
  EvtVector4R pp, pm;
 
  pp = p4b + p4meson;
  pm = p4b - p4meson;
 
  // lange - October 31,2002 - try to lessen the mass dependence of probmax
  double q2max   = p4b.mass2() + p4meson.mass2() - 2.0 * p4b.mass() * p4meson.mass();
  double q2maxin = 1.0 / q2max;
 
  EvtComplex ep_meson_bb[5];
 
  ep_meson_bb[0] = ep_meson_b[0] * ( p4b );
  ep_meson_bb[1] = ep_meson_b[1] * ( p4b );
  ep_meson_bb[2] = ep_meson_b[2] * ( p4b );
  ep_meson_bb[3] = ep_meson_b[3] * ( p4b );
  ep_meson_bb[4] = ep_meson_b[4] * ( p4b );
 
  EvtVector4C tds0, tds1, tds2, tds3, tds4;
 
  EvtTensor4C tds;
  if ( l_num == EM || l_num == MUM || l_num == TAUM )
  {
    EvtTensor4C tdual = EvtComplex( 0.0, hf ) * dual( directProd( pp, pm ) );
    tds0 = tdual.cont2( ep_meson_b[0] ) - kf * ep_meson_b[0] - bpf * ep_meson_bb[0] * pp -
           bmf * ep_meson_bb[0] * pm;
    tds0 *= q2maxin;
 
    tds1 = tdual.cont2( ep_meson_b[1] ) - kf * ep_meson_b[1] - bpf * ep_meson_bb[1] * pp -
           bmf * ep_meson_bb[1] * pm;
    tds1 *= q2maxin;
 
    tds2 = tdual.cont2( ep_meson_b[2] ) - kf * ep_meson_b[2] - bpf * ep_meson_bb[2] * pp -
           bmf * ep_meson_bb[2] * pm;
    tds2 *= q2maxin;
 
    tds3 = tdual.cont2( ep_meson_b[3] ) - kf * ep_meson_b[3] - bpf * ep_meson_bb[3] * pp -
           bmf * ep_meson_bb[3] * pm;
    tds3 *= q2maxin;
 
    tds4 = tdual.cont2( ep_meson_b[4] ) - kf * ep_meson_b[4] - bpf * ep_meson_bb[4] * pp -
           bmf * ep_meson_bb[4] * pm;
    tds4 *= q2maxin;
 
    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 )
    {
      EvtTensor4C tdual = EvtComplex( 0.0, -hf ) * dual( directProd( pp, pm ) );
      tds0 = tdual.cont2( ep_meson_b[0] ) - kf * ep_meson_b[0] - bpf * ep_meson_bb[0] * pp -
             bmf * ep_meson_bb[0] * pm;
      tds0 *= q2maxin;
 
      tds1 = tdual.cont2( ep_meson_b[1] ) - kf * ep_meson_b[1] - bpf * ep_meson_bb[1] * pp -
             bmf * ep_meson_bb[1] * pm;
      tds1 *= q2maxin;
 
      tds2 = tdual.cont2( ep_meson_b[2] ) - kf * ep_meson_b[2] - bpf * ep_meson_bb[2] * pp -
             bmf * ep_meson_bb[2] * pm;
      tds2 *= q2maxin;
 
      tds3 = tdual.cont2( ep_meson_b[3] ) - kf * ep_meson_b[3] - bpf * ep_meson_bb[3] * pp -
             bmf * ep_meson_bb[3] * pm;
      tds3 *= q2maxin;
 
      tds4 = tdual.cont2( ep_meson_b[4] ) - kf * ep_meson_b[4] - bpf * ep_meson_bb[4] * pp -
             bmf * ep_meson_bb[4] * pm;
      tds4 *= q2maxin;
 
      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" ) << "dfnb89agngri wrong lepton number\n"; }
  }
 
  amp.vertex( 0, 0, l1 * tds0 );
  amp.vertex( 0, 1, l2 * tds0 );
 
  amp.vertex( 1, 0, l1 * tds1 );
  amp.vertex( 1, 1, l2 * tds1 );
 
  amp.vertex( 2, 0, l1 * tds2 );
  amp.vertex( 2, 1, l2 * tds2 );
 
  amp.vertex( 3, 0, l1 * tds3 );
  amp.vertex( 3, 1, l2 * tds3 );
 
  amp.vertex( 4, 0, l1 * tds4 );
  amp.vertex( 4, 1, l2 * tds4 );
 
  return;
}