EvtKstarnunu.cpp

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#include "EvtGenModels/EvtKstarnunu.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 EvtKstarnunu::getName()
{
    return "KSTARNUNU";
}

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

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

    //We expect the parent to be a scalar
    //and the daughters to be K neutrino netrino

    checkSpinParent( EvtSpinType::SCALAR );

    checkSpinDaughter( 0, EvtSpinType::VECTOR );
    checkSpinDaughter( 1, EvtSpinType::NEUTRINO );
    checkSpinDaughter( 2, EvtSpinType::NEUTRINO );
}

void EvtKstarnunu::decay( EvtParticle* p )
{
    static EvtId NUE = EvtPDL::getId( "nu_e" );
    static EvtId NUM = EvtPDL::getId( "nu_mu" );
    static EvtId NUT = EvtPDL::getId( "nu_tau" );
    static EvtId NUEB = EvtPDL::getId( "anti-nu_e" );
    static EvtId NUMB = EvtPDL::getId( "anti-nu_mu" );
    static EvtId NUTB = EvtPDL::getId( "anti-nu_tau" );

    p->initializePhaseSpace( getNDaug(), getDaugs() );

    double m_b = p->mass();

    EvtParticle *meson, *neutrino1, *neutrino2;
    meson = p->getDaug( 0 );
    neutrino1 = p->getDaug( 1 );
    neutrino2 = p->getDaug( 2 );
    EvtVector4R momnu1 = neutrino1->getP4();
    EvtVector4R momnu2 = neutrino2->getP4();
    EvtVector4R momkstar = meson->getP4();

    double v0_0, a1_0, a2_0;
    double m2v0, a1_b, a2_b;
    v0_0 = 0.47;
    a1_0 = 0.37;
    a2_0 = 0.40;
    m2v0 = 5. * 5.;
    a1_b = -0.023;
    a2_b = 0.034;

    EvtVector4R q = momnu1 + momnu2;
    double q2 = q.mass2();

    double v0, a1, a2;
    v0 = v0_0 / ( 1 - q2 / m2v0 );
    a1 = a1_0 * ( 1 + a1_b * q2 );
    a2 = a2_0 * ( 1 + a2_b * q2 );

    EvtVector4R p4b;
    p4b.set( m_b, 0., 0., 0. );    // Do calcs in mother rest frame

    double m_k = meson->mass();

    EvtTensor4C tds = ( -2 * v0 / ( m_b + m_k ) ) *
                          dual( EvtGenFunctions::directProd( p4b, momkstar ) ) -
                      EvtComplex( 0.0, 1.0 ) *
                          ( ( m_b + m_k ) * a1 * EvtTensor4C::g() -
                            ( a2 / ( m_b + m_k ) ) *
                                EvtGenFunctions::directProd( p4b - momkstar,
                                                             p4b + momkstar ) );

    EvtVector4C l;

    if ( getDaug( 1 ) == NUE || getDaug( 1 ) == NUM || getDaug( 1 ) == NUT ) {
        l = EvtLeptonVACurrent( neutrino1->spParentNeutrino(),
                                neutrino2->spParentNeutrino() );
    }
    if ( getDaug( 1 ) == NUEB || getDaug( 1 ) == NUMB || getDaug( 1 ) == NUTB ) {
        l = EvtLeptonVACurrent( neutrino2->spParentNeutrino(),
                                neutrino1->spParentNeutrino() );
    }

    EvtVector4C et0, et1, et2;
    et0 = tds.cont1( meson->epsParent( 0 ).conj() );
    et1 = tds.cont1( meson->epsParent( 1 ).conj() );
    et2 = tds.cont1( meson->epsParent( 2 ).conj() );

    vertex( 0, l * et0 );
    vertex( 1, l * et1 );
    vertex( 2, l * et2 );

    return;
}