EvtVSSMix.cpp

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#include "EvtGenModels/EvtVSSMix.hh"

#include "EvtGenBase/EvtConst.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/EvtVector4C.hh"

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

std::string EvtVSSMix::getName()
{
    return "VSS_MIX";
}

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

void EvtVSSMix::init()
{
    // check that there are 1 arguments
    checkNArg( 1 );
    checkNDaug( 2 );

    checkSpinParent( EvtSpinType::VECTOR );

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

void EvtVSSMix::initProbMax()
{
    setProbMax( 0.5 );
}

void EvtVSSMix::decay( EvtParticle* p )
{
    //added by Lange Jan4,2000
    static EvtId B0 = EvtPDL::getId( "B0" );
    static EvtId B0B = EvtPDL::getId( "anti-B0" );

    p->initializePhaseSpace( getNDaug(), getDaugs() );
    EvtParticle *s1, *s2;
    s1 = p->getDaug( 0 );
    s2 = p->getDaug( 1 );
    EvtVector4R s1mom = s1->getP4();

    double t1, t2, dm;

    s1->setLifetime();
    s2->setLifetime();

    t1 = s1->getLifetime();
    t2 = s2->getLifetime();

    //dm should probably be a parameter to this model.

    dm = getArg( 0 ) / EvtConst::c;

    EvtId d1, d2;

    d1 = s1->getId();
    d2 = s2->getId();

    double mix_amp = 0.;
    if ( d1 == B0 && d2 == B0B )
        mix_amp = cos( 0.5 * dm * ( t1 - t2 ) );
    if ( d1 == B0B && d2 == B0 )
        mix_amp = cos( 0.5 * dm * ( t1 - t2 ) );
    if ( d1 == B0 && d2 == B0 )
        mix_amp = sin( 0.5 * dm * ( t1 - t2 ) );
    if ( d1 == B0B && d2 == B0B )
        mix_amp = sin( 0.5 * dm * ( t1 - t2 ) );

    double norm = 1.0 / s1mom.d3mag();

    vertex( 0, norm * mix_amp * s1mom * ( p->eps( 0 ) ) );
    vertex( 1, norm * mix_amp * s1mom * ( p->eps( 1 ) ) );
    vertex( 2, norm * mix_amp * s1mom * ( p->eps( 2 ) ) );

    return;
}

std::string EvtVSSMix::getParamName( int i )
{
    switch ( i ) {
        case 0:
            return "deltaM";
        default:
            return "";
    }
}