EvtSemiLeptonicScalarAmp.cpp

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#include "EvtGenBase/EvtSemiLeptonicScalarAmp.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/EvtPatches.hh"
#include "EvtGenBase/EvtReport.hh"
#include "EvtGenBase/EvtSemiLeptonicFF.hh"
#include "EvtGenBase/EvtTensor4C.hh"
#include "EvtGenBase/EvtVector4C.hh"

void EvtSemiLeptonicScalarAmp::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+" );

    //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 fpf, f0f;
    double mesonmass = parent->getDaug( 0 )->mass();
    double parentmass = parent->mass();

    FormFactors->getscalarff( parent->getId(), parent->getDaug( 0 )->getId(),
                              q2, mesonmass, &fpf, &f0f );

    EvtVector4R p4b;
    p4b.set( parent->mass(), 0.0, 0.0, 0.0 );
    EvtVector4R p4meson = parent->getDaug( 0 )->getP4();
    double mdiffoverq2;
    mdiffoverq2 = parentmass * parentmass - mesonmass * mesonmass;
    mdiffoverq2 = mdiffoverq2 / q2;

    EvtVector4C l1, l2;

    EvtId l_num = parent->getDaug( 1 )->getId();
    EvtVector4C tds;

    if ( l_num == EM || l_num == MUM || l_num == TAUM ) {
        tds = EvtVector4C(
            fpf * ( p4b + p4meson - ( mdiffoverq2 * ( p4b - p4meson ) ) ) +
            +f0f * mdiffoverq2 * ( 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 = EvtVector4C(
                fpf * ( p4b + p4meson - ( mdiffoverq2 * ( p4b - p4meson ) ) ) +
                +f0f * mdiffoverq2 * ( 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 {
            EvtGenReport( EVTGEN_ERROR, "EvtGen" )
                << "dfnb89agngri wrong lepton number\n";
        }
    }

    amp.vertex( 0, l1 * tds );
    amp.vertex( 1, l2 * tds );
}