EvtVtoSll.cpp

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* Copyright 1998-2020 CERN for the benefit of the EvtGen authors       *
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* This file is part of EvtGen.                                         *
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#include "EvtGenModels/EvtVtoSll.hh"

#include "EvtGenBase/EvtDiracSpinor.hh"
#include "EvtGenBase/EvtGenKine.hh"
#include "EvtGenBase/EvtPDL.hh"
#include "EvtGenBase/EvtParticle.hh"
#include "EvtGenBase/EvtPatches.hh"
#include "EvtGenBase/EvtReport.hh"
#include "EvtGenBase/EvtTensor4C.hh"
#include "EvtGenBase/EvtVector4C.hh"

#include <iostream>
#include <stdlib.h>
#include <string>

std::string EvtVtoSll::getName()
{
    return "VTOSLL";
}

EvtDecayBase* EvtVtoSll::clone()
{
    return new EvtVtoSll;
}

void EvtVtoSll::init()
{
    // check that there are 0 arguments
    checkNArg( 0 );
    checkNDaug( 3 );

    checkSpinParent( EvtSpinType::VECTOR );

    checkSpinDaughter( 0, EvtSpinType::SCALAR );
    checkSpinDaughter( 1, EvtSpinType::DIRAC );
    checkSpinDaughter( 2, EvtSpinType::DIRAC );
}

void EvtVtoSll::initProbMax()
{
    //setProbMax(1.0);
}

void EvtVtoSll::decay( EvtParticle* p )
{
    p->initializePhaseSpace( getNDaug(), getDaugs() );

    EvtParticle *l1, *l2;
    l1 = p->getDaug( 1 );
    l2 = p->getDaug( 2 );

    EvtVector4C l11, l12, l21, l22;
    l11 = EvtLeptonVCurrent( l1->spParent( 0 ), l2->spParent( 0 ) );
    l12 = EvtLeptonVCurrent( l1->spParent( 0 ), l2->spParent( 1 ) );
    l21 = EvtLeptonVCurrent( l1->spParent( 1 ), l2->spParent( 0 ) );
    l22 = EvtLeptonVCurrent( l1->spParent( 1 ), l2->spParent( 1 ) );

    EvtVector4C eps0 = p->eps( 0 );
    EvtVector4C eps1 = p->eps( 1 );
    EvtVector4C eps2 = p->eps( 2 );

    EvtVector4R P = p->getP4Restframe();
    EvtVector4R k = l1->getP4() + l2->getP4();
    double k2 = k * k;

    EvtTensor4C T( dual( EvtGenFunctions::directProd( P, ( 1.0 / k2 ) * k ) ) );

    double M2 = p->mass();
    M2 *= M2;
    double m2 = l1->mass();
    m2 *= m2;

    double norm = 1.0 / sqrt( 2 * M2 + 4 * m2 - 4 * m2 * m2 / M2 );

    vertex( 0, 0, 0, norm * ( eps0 * T.cont2( l11 ) ) );
    vertex( 0, 0, 1, norm * ( eps0 * T.cont2( l12 ) ) );
    vertex( 0, 1, 0, norm * ( eps0 * T.cont2( l21 ) ) );
    vertex( 0, 1, 1, norm * ( eps0 * T.cont2( l22 ) ) );

    vertex( 1, 0, 0, norm * ( eps1 * T.cont2( l11 ) ) );
    vertex( 1, 0, 1, norm * ( eps1 * T.cont2( l12 ) ) );
    vertex( 1, 1, 0, norm * ( eps1 * T.cont2( l21 ) ) );
    vertex( 1, 1, 1, norm * ( eps1 * T.cont2( l22 ) ) );

    vertex( 2, 0, 0, norm * ( eps2 * T.cont2( l11 ) ) );
    vertex( 2, 0, 1, norm * ( eps2 * T.cont2( l12 ) ) );
    vertex( 2, 1, 0, norm * ( eps2 * T.cont2( l21 ) ) );
    vertex( 2, 1, 1, norm * ( eps2 * T.cont2( l22 ) ) );

    return;
}