EvtCPUtil.cpp

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#include "EvtGenBase/EvtCPUtil.hh"

#include "EvtGenBase/EvtConst.hh"
#include "EvtGenBase/EvtPDL.hh"
#include "EvtGenBase/EvtParticle.hh"
#include "EvtGenBase/EvtPatches.hh"
#include "EvtGenBase/EvtRandom.hh"
#include "EvtGenBase/EvtReport.hh"
#include "EvtGenBase/EvtScalarParticle.hh"
#include "EvtGenBase/EvtSymTable.hh"

#include <assert.h>
#include <stdio.h>
#include <stdlib.h>
using std::endl;

EvtCPUtil::EvtCPUtil( int mixingType )
{
    _enableFlip = false;
    _mixingType = mixingType;
}

EvtCPUtil* EvtCPUtil::getInstance()
{
    static EvtCPUtil* theCPUtil = 0;

    if ( theCPUtil == 0 ) {
        theCPUtil = new EvtCPUtil( 1 );
    }

    return theCPUtil;
}

//added two functions for finding the fraction of B0 tags for decays into
//both CP eigenstates and non-CP eigenstates -- NK, Jan. 27th, 1998

void EvtCPUtil::fractB0CP( EvtComplex Af, EvtComplex Abarf, double /*deltam*/,
                           double beta, double& fract )
{
    //This function returns the number of B0 tags for decays into CP-eigenstates
    //(the "probB0" in the new EvtOtherB)

    //double gamma_B = EvtPDL::getWidth(B0);
    //double xd = deltam/gamma_B;
    //double xd = 0.65;
    double ratio = 1 / ( 1 + 0.65 * 0.65 );

    EvtComplex rf, rbarf;

    rf = EvtComplex( cos( 2.0 * beta ), sin( 2.0 * beta ) ) * Abarf / Af;
    rbarf = EvtComplex( 1.0 ) / rf;

    double A2 = real( Af ) * real( Af ) + imag( Af ) * imag( Af );
    double Abar2 = real( Abarf ) * real( Abarf ) + imag( Abarf ) * imag( Abarf );

    double rf2 = real( rf ) * real( rf ) + imag( rf ) * imag( rf );
    double rbarf2 = real( rbarf ) * real( rbarf ) + imag( rbarf ) * imag( rbarf );

    fract = ( Abar2 * ( 1 + rbarf2 + ( 1 - rbarf2 ) * ratio ) ) /
            ( Abar2 * ( 1 + rbarf2 + ( 1 - rbarf2 ) * ratio ) +
              A2 * ( 1 + rf2 + ( 1 - rf2 ) * ratio ) );
    return;
}

void EvtCPUtil::fractB0nonCP( EvtComplex Af, EvtComplex Abarf, EvtComplex Afbar,
                              EvtComplex Abarfbar, double deltam, double beta,
                              int flip, double& fract )
{
    //this function returns the number of B0 tags for decays into non-CP eigenstates
    //(the "probB0" in the new EvtOtherB)
    //this needs more thought...

    //double gamma_B = EvtPDL::getWidth(B0);
    //EvtGenReport(EVTGEN_INFO,"EvtGen") << "gamma " << gamma_B<< endl;
    //double xd = deltam/gamma_B;

    //why is the width of B0 0 in PDL??

    double xd = 0.65;
    double gamma_B = deltam / xd;
    double IAf, IAfbar, IAbarf, IAbarfbar;
    EvtComplex rf, rfbar, rbarf, rbarfbar;
    double rf2, rfbar2, rbarf2, rbarfbar2;
    double Af2, Afbar2, Abarf2, Abarfbar2;

    rf = EvtComplex( cos( 2.0 * beta ), sin( 2.0 * beta ) ) * Abarf / Af;
    rfbar = EvtComplex( cos( 2.0 * beta ), sin( 2.0 * beta ) ) * Abarfbar / Afbar;
    rbarf = EvtComplex( cos( -2.0 * beta ), sin( -2.0 * beta ) ) * Af / Abarf;
    rbarfbar = EvtComplex( cos( -2.0 * beta ), sin( -2.0 * beta ) ) * Afbar /
               Abarfbar;

    rf2 = real( rf ) * real( rf ) + imag( rf ) * imag( rf );
    rfbar2 = real( rfbar ) * real( rfbar ) + imag( rfbar ) * imag( rfbar );
    rbarf2 = real( rbarf ) * real( rbarf ) + imag( rbarf ) * imag( rbarf );
    rbarfbar2 = real( rbarfbar ) * real( rbarfbar ) +
                imag( rbarfbar ) * imag( rbarfbar );

    Af2 = real( Af ) * real( Af ) + imag( Af ) * imag( Af );
    Afbar2 = real( Afbar ) * real( Afbar ) + imag( Afbar ) * imag( Afbar );
    Abarf2 = real( Abarf ) * real( Abarf ) + imag( Abarf ) * imag( Abarf );
    Abarfbar2 = real( Abarfbar ) * real( Abarfbar ) +
                imag( Abarfbar ) * imag( Abarfbar );

    //
    //IAf = integral(gamma(B0->f)), etc.
    //

    IAf = ( Af2 / ( 2 * gamma_B ) ) * ( 1 + rf2 + ( 1 - rf2 ) / ( 1 + xd * xd ) );
    IAfbar = ( Afbar2 / ( 2 * gamma_B ) ) *
             ( 1 + rfbar2 + ( 1 - rfbar2 ) / ( 1 + xd * xd ) );
    IAbarf = ( Abarf2 / ( 2 * gamma_B ) ) *
             ( 1 + rbarf2 + ( 1 - rbarf2 ) / ( 1 + xd * xd ) );
    IAbarfbar = ( Abarfbar2 / ( 2 * gamma_B ) ) *
                ( 1 + rbarfbar2 + ( 1 - rbarfbar2 ) / ( 1 + xd * xd ) );

    //flip specifies the relative fraction of fbar events

    fract = IAbarf / ( IAbarf + IAf ) + flip * IAbarfbar / ( IAfbar + IAbarfbar );

    return;
}

void EvtCPUtil::OtherB( EvtParticle* p, double& t, EvtId& otherb, double probB0 )
{
    if ( _mixingType == EvtCPUtil::Coherent ) {
        OtherCoherentB( p, t, otherb, probB0 );

    } else if ( _mixingType == EvtCPUtil::Incoherent ) {
        OtherIncoherentB( p, t, otherb, probB0 );
    }
}

void EvtCPUtil::OtherCoherentB( EvtParticle* p, double& t, EvtId& otherb,
                                double probB0 )
{
    //Can not call this recursively!!!
    static int entryCount = 0;
    entryCount++;

    //added by Lange Jan4,2000
    static EvtId B0B = EvtPDL::getId( "anti-B0" );
    static EvtId B0 = EvtPDL::getId( "B0" );
    static EvtId BSB = EvtPDL::getId( "anti-B_s0" );
    static EvtId BS = EvtPDL::getId( "B_s0" );

    static EvtId UPS4S = EvtPDL::getId( "Upsilon(4S)" );

    int isB0 = EvtRandom::Flat( 0.0, 1.0 ) < probB0;

    int idaug;

    p->setLifetime();

    // now get the time between the decay of this B and the other B!

    EvtParticle* parent = p->getParent();

    EvtParticle* other;

    bool incoherentmix = false;

    if ( ( parent != 0 ) && ( parent->getId() == B0 || parent->getId() == B0B ||
                              parent->getId() == BS || parent->getId() == BSB ) ) {
        incoherentmix = true;
    }

    if ( incoherentmix )
        parent = parent->getParent();

    if ( parent == 0 || parent->getId() != UPS4S ) {
        //Need to make this more general, but for now
        //assume no parent. If we have parent of B we
        //need to charge conj. full decay tree.

        if ( parent != 0 ) {
            EvtGenReport( EVTGEN_INFO, "EvtGen" )
                << "p=" << EvtPDL::name( p->getId() )
                << " parent=" << EvtPDL::name( parent->getId() ) << endl;
        }
        assert( parent == 0 );
        p->setLifetime();
        t = p->getLifetime();
        bool needToChargeConj = false;
        if ( p->getId() == B0B && isB0 )
            needToChargeConj = true;
        if ( p->getId() == B0 && !isB0 )
            needToChargeConj = true;
        if ( p->getId() == BSB && isB0 )
            needToChargeConj = true;
        if ( p->getId() == BS && !isB0 )
            needToChargeConj = true;

        if ( needToChargeConj ) {
            p->setId( EvtPDL::chargeConj( p->getId() ) );
            if ( incoherentmix ) {
                p->getDaug( 0 )->setId(
                    EvtPDL::chargeConj( p->getDaug( 0 )->getId() ) );
            }
        }
        otherb = EvtPDL::chargeConj( p->getId() );

        entryCount--;
        return;
    } else {
        if ( parent->getDaug( 0 ) != p ) {
            other = parent->getDaug( 0 );
            idaug = 0;
        } else {
            other = parent->getDaug( 1 );
            idaug = 1;
        }
    }

    if ( parent != 0 ) {
        //if (entryCount>1){
        //  EvtGenReport(EVTGEN_INFO,"EvtGen") << "Double CP decay:"<<entryCount<<endl;
        //}

        //kludge!! Lange Mar21, 2003
        // if the other B is an alias... don't change the flavor..
        if ( other->getId().isAlias() ) {
            OtherB( p, t, otherb );
            entryCount--;
            return;
        }

        if ( entryCount == 1 ) {
            EvtVector4R p_init = other->getP4();
            //int decayed=other->getNDaug()>0;
            bool decayed = other->isDecayed();

            other->deleteTree();

            EvtScalarParticle* scalar_part;

            scalar_part = new EvtScalarParticle;
            if ( isB0 ) {
                scalar_part->init( B0, p_init );
            } else {
                scalar_part->init( B0B, p_init );
            }
            other = (EvtParticle*)scalar_part;
            //    other->set_type(EvtSpinType::SCALAR);
            other->setDiagonalSpinDensity();

            parent->insertDaugPtr( idaug, other );

            if ( decayed ) {
                //EvtGenReport(EVTGEN_INFO,"EvtGen") << "In CP Util calling decay \n";
                other->decay();
            }
        }

        otherb = other->getId();

        other->setLifetime();
        t = p->getLifetime() - other->getLifetime();

        otherb = other->getId();

    } else {
        EvtGenReport( EVTGEN_INFO, "EvtGen" )
            << "We have an error here!!!!" << endl;
        otherb = EvtId( -1, -1 );
    }

    entryCount--;
    return;
}

// ========================================================================
bool EvtCPUtil::isBsMixed( EvtParticle* p )
{
    if ( !( p->getParent() ) )
        return false;

    static EvtId BS0 = EvtPDL::getId( "B_s0" );
    static EvtId BSB = EvtPDL::getId( "anti-B_s0" );

    if ( ( p->getId() != BS0 ) && ( p->getId() != BSB ) )
        return false;

    if ( ( p->getParent()->getId() == BS0 ) || ( p->getParent()->getId() == BSB ) )
        return true;

    return false;
}

// ========================================================================
bool EvtCPUtil::isB0Mixed( EvtParticle* p )
{
    if ( !( p->getParent() ) )
        return false;

    static EvtId B0 = EvtPDL::getId( "B0" );
    static EvtId B0B = EvtPDL::getId( "anti-B0" );

    if ( ( p->getId() != B0 ) && ( p->getId() != B0B ) )
        return false;

    if ( ( p->getParent()->getId() == B0 ) || ( p->getParent()->getId() == B0B ) )
        return true;

    return false;
}
//============================================================================
// Return the tag of the event (ie the anti-flavour of the produced
// B meson). Flip the flavour of the event with probB probability
//============================================================================
void EvtCPUtil::OtherIncoherentB( EvtParticle* p, double& t, EvtId& otherb,
                                  double probB )
{
    //std::cout<<"New routine running"<<endl;
    //if(p->getId() == B0 || p->getId() == B0B)
    //added by liming Zhang
    enableFlip();
    if ( ( isB0Mixed( p ) ) || ( isBsMixed( p ) ) ) {
        p->getParent()->setLifetime();
        t = p->getParent()->getLifetime();
    } else {
        p->setLifetime();
        t = p->getLifetime();
    }

    if ( flipIsEnabled() ) {
        //std::cout << " liming << flipIsEnabled " << std::endl;
        // Flip the flavour of the particle with probability probB
        bool isFlipped = ( EvtRandom::Flat( 0., 1. ) < probB );

        if ( isFlipped ) {
            if ( ( isB0Mixed( p ) ) || ( isBsMixed( p ) ) ) {
                p->getParent()->setId(
                    EvtPDL::chargeConj( p->getParent()->getId() ) );
                p->setId( EvtPDL::chargeConj( p->getId() ) );
            } else {
                p->setId( EvtPDL::chargeConj( p->getId() ) );
            }
        }
    }

    if ( ( isB0Mixed( p ) ) || ( isBsMixed( p ) ) ) {
        // if B has mixed, tag flavour is charge conjugate of parent of B-meson
        otherb = EvtPDL::chargeConj( p->getParent()->getId() );
    } else {
        // else it is opposite flavour than this B hadron
        otherb = EvtPDL::chargeConj( p->getId() );
    }

    return;
}
//============================================================================
void EvtCPUtil::OtherB( EvtParticle* p, double& t, EvtId& otherb )
{
    static EvtId BSB = EvtPDL::getId( "anti-B_s0" );
    static EvtId BS0 = EvtPDL::getId( "B_s0" );
    static EvtId B0B = EvtPDL::getId( "anti-B0" );
    static EvtId B0 = EvtPDL::getId( "B0" );
    static EvtId D0B = EvtPDL::getId( "anti-D0" );
    static EvtId D0 = EvtPDL::getId( "D0" );
    static EvtId UPS4 = EvtPDL::getId( "Upsilon(4S)" );

    if ( p->getId() == BS0 || p->getId() == BSB ) {
        static double ctauL = EvtPDL::getctau( EvtPDL::getId( "B_s0L" ) );
        static double ctauH = EvtPDL::getctau( EvtPDL::getId( "B_s0H" ) );
        static double ctau = ctauL < ctauH ? ctauH : ctauL;
        t = -log( EvtRandom::Flat() ) * ctau;
        EvtParticle* parent = p->getParent();
        if ( parent != 0 && ( parent->getId() == BS0 || parent->getId() == BSB ) ) {
            if ( parent->getId() == BS0 )
                otherb = BSB;
            if ( parent->getId() == BSB )
                otherb = BS0;
            parent->setLifetime( t );
            return;
        }
        if ( p->getId() == BS0 )
            otherb = BSB;
        if ( p->getId() == BSB )
            otherb = BS0;
        p->setLifetime( t );
        return;
    }

    if ( p->getId() == D0 || p->getId() == D0B ) {
        static double ctauL = EvtPDL::getctau( EvtPDL::getId( "D0L" ) );
        static double ctauH = EvtPDL::getctau( EvtPDL::getId( "D0H" ) );
        static double ctau = ctauL < ctauH ? ctauH : ctauL;
        t = -log( EvtRandom::Flat() ) * ctau;
        EvtParticle* parent = p->getParent();
        if ( parent != 0 && ( parent->getId() == D0 || parent->getId() == D0B ) ) {
            if ( parent->getId() == D0 )
                otherb = D0B;
            if ( parent->getId() == D0B )
                otherb = D0;
            parent->setLifetime( t );
            return;
        }
        if ( p->getId() == D0 )
            otherb = D0B;
        if ( p->getId() == D0B )
            otherb = D0;
        p->setLifetime( t );
        return;
    }

    p->setLifetime();

    // now get the time between the decay of this B and the other B!

    EvtParticle* parent = p->getParent();

    if ( parent == 0 || parent->getId() != UPS4 ) {
        //EvtGenReport(EVTGEN_ERROR,"EvtGen") <<
        //  "Warning CP violation with B having no parent!"<<endl;
        t = p->getLifetime();
        if ( p->getId() == B0 )
            otherb = B0B;
        if ( p->getId() == B0B )
            otherb = B0;
        if ( p->getId() == BS0 )
            otherb = BSB;
        if ( p->getId() == BSB )
            otherb = BS0;
        return;
    } else {
        if ( parent->getDaug( 0 ) != p ) {
            otherb = parent->getDaug( 0 )->getId();
            parent->getDaug( 0 )->setLifetime();
            t = p->getLifetime() - parent->getDaug( 0 )->getLifetime();
        } else {
            otherb = parent->getDaug( 1 )->getId();
            parent->getDaug( 1 )->setLifetime();
            t = p->getLifetime() - parent->getDaug( 1 )->getLifetime();
        }
    }

    return;
}

// No CP violation is assumed
void EvtCPUtil::incoherentMix( const EvtId id, double& t, int& mix )
{
    int stdHepNum = EvtPDL::getStdHep( id );
    stdHepNum = abs( stdHepNum );

    EvtId partId = EvtPDL::evtIdFromStdHep( stdHepNum );

    std::string partName = EvtPDL::name( partId );
    std::string hname = partName + std::string( "H" );
    std::string lname = partName + std::string( "L" );

    EvtId lId = EvtPDL::getId( lname );
    EvtId hId = EvtPDL::getId( hname );

    double ctauL = EvtPDL::getctau( lId );
    double ctauH = EvtPDL::getctau( hId );

    // Bug Fixed: Corrected the average as gamma is the relevent parameter
    double ctau = 2.0 * ( ctauL * ctauH ) / ( ctauL + ctauH );
    //double ctau=0.5*(ctauL+ctauH);

    // Bug Fixed: ctau definition changed above
    //double y=(ctauH-ctauL)/(2*ctau);
    double y = ( ctauH - ctauL ) / ( ctauH + ctauL );

    //deltam and qoverp defined in DECAY.DEC

    std::string qoverpParmName = std::string( "qoverp_incohMix_" ) + partName;
    std::string mdParmName = std::string( "dm_incohMix_" ) + partName;
    int ierr;
    double qoverp = atof( EvtSymTable::get( qoverpParmName, ierr ).c_str() );
    double x = atof( EvtSymTable::get( mdParmName, ierr ).c_str() ) * ctau /
               EvtConst::c;
    double fac;

    if ( id == partId ) {
        fac = 1.0 / ( qoverp * qoverp );
    } else {
        fac = qoverp * qoverp;
    }

    double mixprob = ( x * x + y * y ) /
                     ( x * x + y * y + fac * ( 2.0 + x * x - y * y ) );

    int mixsign;

    mixsign = ( mixprob > EvtRandom::Flat( 0.0, 1.0 ) ) ? -1 : 1;

    double prob;

    // Find the longest of the two lifetimes
    double ctaulong = ctauL <= ctauH ? ctauH : ctauL;

    // Bug fixed: Ensure cosine argument is dimensionless so /ctau
    do {
        t = -log( EvtRandom::Flat() ) * ctaulong;
        prob = 1.0 + exp( -2.0 * fabs( y ) * t / ctau ) +
               mixsign * 2.0 * exp( -fabs( y ) * t / ctau ) * cos( x * t / ctau );
    } while ( prob < 4.0 * EvtRandom::Flat() );

    mix = 0;

    if ( mixsign == -1 )
        mix = 1;

    return;
}

double EvtCPUtil::getDeltaGamma( const EvtId id )
{
    int stdHepNum = EvtPDL::getStdHep( id );
    stdHepNum = abs( stdHepNum );
    EvtId partId = EvtPDL::evtIdFromStdHep( stdHepNum );

    std::string partName = EvtPDL::name( partId );
    std::string hname = partName + std::string( "H" );
    std::string lname = partName + std::string( "L" );

    EvtId lId = EvtPDL::getId( lname );
    EvtId hId = EvtPDL::getId( hname );

    double ctauL = EvtPDL::getctau( lId );
    double ctauH = EvtPDL::getctau( hId );

    double dGamma = ( 1 / ctauL - 1 / ctauH ) * EvtConst::c;
    return dGamma;
}

double EvtCPUtil::getDeltaM( const EvtId id )
{
    int stdHepNum = EvtPDL::getStdHep( id );
    stdHepNum = abs( stdHepNum );
    EvtId partId = EvtPDL::evtIdFromStdHep( stdHepNum );

    std::string partName = EvtPDL::name( partId );
    std::string parmName = std::string( "dm_incohMix_" ) + partName;

    int ierr;
    double dM = atof( EvtSymTable::get( parmName, ierr ).c_str() );
    return dM;
}

bool EvtCPUtil::flipIsEnabled()
{
    return _enableFlip;
}
void EvtCPUtil::enableFlip()
{
    _enableFlip = true;
}
void EvtCPUtil::disableFlip()
{
    _enableFlip = false;
}