EvtSVSCPLH.cpp

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#include "EvtGenModels/EvtSVSCPLH.hh"
 
#include "EvtGenBase/EvtCPUtil.hh"
#include "EvtGenBase/EvtConst.hh"
#include "EvtGenBase/EvtGenKine.hh"
#include "EvtGenBase/EvtId.hh"
#include "EvtGenBase/EvtPDL.hh"
#include "EvtGenBase/EvtParticle.hh"
#include "EvtGenBase/EvtReport.hh"
#include "EvtGenBase/EvtVector4C.hh"
 
#include <stdlib.h>
#include <string>
using std::endl;
 
std::string EvtSVSCPLH::getName() const
{
    return "SVS_CPLH";
}
 
EvtDecayBase* EvtSVSCPLH::clone() const
{
    return new EvtSVSCPLH;
}
 
void EvtSVSCPLH::init()
{
    // check that there are 8 arguments
    checkNArg( 8 );
    checkNDaug( 2 );
 
    checkSpinParent( EvtSpinType::SCALAR );
 
    checkSpinDaughter( 0, EvtSpinType::VECTOR );
    checkSpinDaughter( 1, EvtSpinType::SCALAR );
 
    static const double ctau = EvtPDL::getctau( EvtPDL::getId( "B0" ) );
 
    // hbar/s
    m_dm = getArg( 0 );
    m_dgamma = EvtConst::c * getArg( 1 ) / ctau;
 
    m_qop = getArg( 2 ) * exp( EvtComplex( 0.0, getArg( 3 ) ) );
 
    m_poq = 1.0 / m_qop;
 
    m_Af = getArg( 4 ) * exp( EvtComplex( 0.0, getArg( 5 ) ) );
    m_Abarf = getArg( 6 ) * exp( EvtComplex( 0.0, getArg( 7 ) ) );
 
    if ( verbose() ) {
        EvtGenReport( EVTGEN_INFO, "EvtGen" )
            << ":EvtSVSCPLH:dm=" << m_dm << endl;
        EvtGenReport( EVTGEN_INFO, "EvtGen" )
            << ":EvtSVSCPLH:dGamma=" << m_dgamma << endl;
        EvtGenReport( EVTGEN_INFO, "EvtGen" )
            << ":EvtSVSCPLH:q/p=" << m_qop << endl;
        EvtGenReport( EVTGEN_INFO, "EvtGen" )
            << ":EvtSVSCPLH:Af=" << m_Af << endl;
        EvtGenReport( EVTGEN_INFO, "EvtGen" )
            << ":EvtSVSCPLH:Abarf=" << m_Abarf << endl;
    }
}
 
void EvtSVSCPLH::initProbMax()
{
    //This is probably not quite right, but it should do as a start...
    //Anders
 
    setProbMax( 4.0 * ( getArg( 4 ) * getArg( 4 ) + getArg( 6 ) * getArg( 6 ) ) );
}
 
void EvtSVSCPLH::decay( EvtParticle* p )
{
    p->initializePhaseSpace( getNDaug(), getDaugs() );
 
    static const EvtId B0 = EvtPDL::getId( "B0" );
    static const EvtId B0B = EvtPDL::getId( "anti-B0" );
 
    double t;
    EvtId other_b;
 
    EvtCPUtil::getInstance()->OtherB( p, t, other_b, 0.5 );
 
    //convert time from mm to seconds
    t /= EvtConst::c;
 
    //sign convention is dm=Mheavy-Mlight
    //                   dGamma=Gammalight-Gammaheavy
    //such that in the standard model both of these are positive.
    EvtComplex gp =
        0.5 * ( exp( EvtComplex( 0.25 * t * m_dgamma, -0.5 * t * m_dm ) ) +
                exp( EvtComplex( -0.25 * t * m_dgamma, 0.5 * t * m_dm ) ) );
    EvtComplex gm =
        0.5 * ( exp( EvtComplex( 0.25 * t * m_dgamma, -0.5 * t * m_dm ) ) -
                exp( EvtComplex( -0.25 * t * m_dgamma, 0.5 * t * m_dm ) ) );
 
    EvtComplex amp;
 
    if ( other_b == B0B ) {
        amp = gp * m_Af + m_qop * gm * m_Abarf;
    } else if ( other_b == B0 ) {
        amp = gp * m_Abarf + m_poq * gm * m_Af;
    } else {
        EvtGenReport( EVTGEN_ERROR, "EvtGen" )
            << "other_b was not B0 or B0B!" << endl;
        ::abort();
    }
 
    EvtVector4R p4_parent = p->getP4Restframe();
    ;
 
    double norm = p->getDaug( 0 )->mass() /
                  ( p->getDaug( 0 )->getP4().d3mag() * p4_parent.mass() );
 
    EvtParticle* v = p->getDaug( 0 );
 
    vertex( 0, amp * norm * ( p4_parent * ( v->epsParent( 0 ) ) ) );
    vertex( 1, amp * norm * ( p4_parent * ( v->epsParent( 1 ) ) ) );
    vertex( 2, amp * norm * ( p4_parent * ( v->epsParent( 2 ) ) ) );
 
    return;
}