EvtMassAmp.cpp

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#include "EvtGenBase/EvtMassAmp.hh"
 
EvtMassAmp::EvtMassAmp( const EvtPropBreitWignerRel& prop,
                        const EvtTwoBodyVertex& vd ) :
    EvtAmplitude<EvtPoint1D>(),
    m_prop( prop ),
    m_vd( vd ),
    m_useBirthFact( false ),
    m_useDeathFact( false ),
    m_useBirthFactFF( false ),
    m_useDeathFactFF( false )
{
}
 
EvtMassAmp::EvtMassAmp( const EvtMassAmp& other ) :
    EvtAmplitude<EvtPoint1D>( other ),
    m_prop( other.m_prop ),
    m_vd( other.m_vd ),
    m_vb( other.m_vb ? new EvtTwoBodyVertex( *other.m_vb ) : nullptr ),
    m_useBirthFact( other.m_useBirthFact ),
    m_useDeathFact( other.m_useDeathFact ),
    m_useBirthFactFF( other.m_useBirthFactFF ),
    m_useDeathFactFF( other.m_useDeathFactFF )
{
}
 
EvtMassAmp& EvtMassAmp::operator=( const EvtMassAmp& other )
{
    EvtAmplitude<EvtPoint1D>::operator=( other );
    m_prop = other.m_prop;
    m_vd = other.m_vd;
    m_vb.reset( other.m_vb ? new EvtTwoBodyVertex( *other.m_vb ) : nullptr );
    m_useBirthFact = other.m_useBirthFact;
    m_useDeathFact = other.m_useDeathFact;
    m_useBirthFactFF = other.m_useBirthFactFF;
    m_useDeathFactFF = other.m_useDeathFactFF;
    return *this;
}
 
EvtComplex EvtMassAmp::amplitude( const EvtPoint1D& p ) const
{
    // Modified vertex
 
    double m = p.value();
    // keep things from crashing..
 
    if ( m < ( m_vd.mA() + m_vd.mB() ) )
        return EvtComplex( 0., 0. );
 
    EvtTwoBodyKine vd( m_vd.mA(), m_vd.mB(), m );
 
    // Compute mass-dependent width for relativistic propagator
 
    EvtPropBreitWignerRel bw( m_prop.m0(), m_prop.g0() * m_vd.widthFactor( vd ) );
    EvtComplex amp = bw.evaluate( m );
 
    // Birth vertex factors
 
    if ( m_useBirthFact ) {
        assert( m_vb );
        if ( ( m + m_vb->mB() ) < m_vb->mAB() ) {
            EvtTwoBodyKine vb( m, m_vb->mB(), m_vb->mAB() );
            amp *= m_vb->phaseSpaceFactor( vb, EvtTwoBodyKine::AB );
            amp *= sqrt( ( vb.p() / m_vb->pD() ) );
 
            if ( m_useBirthFactFF ) {
                assert( m_vb );
                amp *= m_vb->formFactor( vb );
            }
        } else {
            if ( m_vb->L() != 0 )
                amp = 0.;
        }
    }
 
    // Decay vertex factors
 
    if ( m_useDeathFact ) {
        amp *= m_vd.phaseSpaceFactor( vd, EvtTwoBodyKine::AB );
        amp *= sqrt( ( vd.p() / m_vd.pD() ) );
    }
    if ( m_useDeathFactFF )
        amp *= m_vd.formFactor( vd );
 
    return amp;
}