EvtSemiLeptonicTensorAmp.cpp

Go to the documentation of this file.

 
/***********************************************************************
* Copyright 1998-2020 CERN for the benefit of the EvtGen authors       *
*                                                                      *
* This file is part of EvtGen.                                         *
*                                                                      *
* EvtGen is free software: you can redistribute it and/or modify       *
* it under the terms of the GNU General Public License as published by *
* the Free Software Foundation, either version 3 of the License, or    *
* (at your option) any later version.                                  *
*                                                                      *
* EvtGen is distributed in the hope that it will be useful,            *
* but WITHOUT ANY WARRANTY; without even the implied warranty of       *
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the        *
* GNU General Public License for more details.                         *
*                                                                      *
* You should have received a copy of the GNU General Public License    *
* along with EvtGen.  If not, see <https://www.gnu.org/licenses/>.     *
***********************************************************************/
 
#include "EvtGenBase/EvtSemiLeptonicTensorAmp.hh"
 
#include "EvtGenBase/EvtAmp.hh"
#include "EvtGenBase/EvtDiracSpinor.hh"
#include "EvtGenBase/EvtGenKine.hh"
#include "EvtGenBase/EvtId.hh"
#include "EvtGenBase/EvtPDL.hh"
#include "EvtGenBase/EvtParticle.hh"
#include "EvtGenBase/EvtReport.hh"
#include "EvtGenBase/EvtSemiLeptonicFF.hh"
#include "EvtGenBase/EvtTensor4C.hh"
#include "EvtGenBase/EvtVector4C.hh"
 
void EvtSemiLeptonicTensorAmp::CalcAmp( EvtParticle* parent, EvtAmp& amp,
                                        EvtSemiLeptonicFF* FormFactors )
{
    static const EvtId EM = EvtPDL::getId( "e-" );
    static const EvtId MUM = EvtPDL::getId( "mu-" );
    static const EvtId TAUM = EvtPDL::getId( "tau-" );
    static const EvtId EP = EvtPDL::getId( "e+" );
    static const EvtId MUP = EvtPDL::getId( "mu+" );
    static const EvtId TAUP = EvtPDL::getId( "tau+" );
 
    static const EvtId D0 = EvtPDL::getId( "D0" );
    static const EvtId D0B = EvtPDL::getId( "anti-D0" );
    static const EvtId DP = EvtPDL::getId( "D+" );
    static const EvtId DM = EvtPDL::getId( "D-" );
    static const EvtId DSM = EvtPDL::getId( "D_s-" );
    static const 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( EvtGenFunctions::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( EvtGenFunctions::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 {
            EvtGenReport( EVTGEN_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;
}