EvtPto3P.cpp

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#include "EvtGenModels/EvtPto3P.hh"

#include "EvtGenBase/EvtPDL.hh"
#include "EvtGenBase/EvtPatches.hh"
#include "EvtGenBase/EvtPto3PAmpFactory.hh"
using namespace EvtCyclic3;

EvtDalitzPlot EvtPto3P::dp()
{
    // There must be 3 daughters. All particles must be pseudoscalars.
    // Charge must be conserved. Number of arguments must be non-zero.

    EvtId parent = getParentId();
    assert( getNDaug() == 3 );
    EvtId dau0 = getDaug( 0 );
    EvtId dau1 = getDaug( 1 );
    EvtId dau2 = getDaug( 2 );

    assert( EvtPDL::getSpinType( parent ) == EvtSpinType::SCALAR );
    assert( EvtPDL::getSpinType( dau0 ) == EvtSpinType::SCALAR );
    assert( EvtPDL::getSpinType( dau1 ) == EvtSpinType::SCALAR );
    assert( EvtPDL::getSpinType( dau2 ) == EvtSpinType::SCALAR );
    assert( EvtPDL::chg3( parent ) ==
            EvtPDL::chg3( dau0 ) + EvtPDL::chg3( dau1 ) + EvtPDL::chg3( dau2 ) );
    assert( getNArg() > 0 );

    return EvtDalitzPlot( EvtPDL::getMass( dau0 ), EvtPDL::getMass( dau1 ),
                          EvtPDL::getMass( dau2 ), EvtPDL::getMass( parent ) );
}

EvtAmpFactory<EvtDalitzPoint>* EvtPto3P::createFactory(
    const EvtMultiChannelParser& parser )
{
    // Compute the interval size

    EvtDalitzPlot plot = dp();
    EvtAmpFactory<EvtDalitzPoint>* fact = new EvtPto3PAmpFactory( plot );
    fact->build( parser, 10000 );
    return fact;
}

std::vector<EvtVector4R> EvtPto3P::initDaughters( const EvtDalitzPoint& x ) const
{
    std::vector<EvtVector4R> v;
    assert( x.isValid() );

    // Calculate in the r.f. of AB

    double eA = x.e( A, AB );
    double eB = x.e( B, AB );
    double eC = x.e( C, AB );
    double pA = x.p( A, AB );
    double pC = x.p( C, AB );
    double cos = x.cosTh( CA, AB );
    double sin = sqrt( 1.0 - cos * cos );

    EvtVector4R vA( eA, 0, 0, pA );
    EvtVector4R vB( eB, 0, 0, -pA );
    EvtVector4R vC( eC, 0, pC * sin, pC * cos );

    // Boost from rest frame of AB to rest-frame of decaying particle
    // vboost is the 4-momentum of frame being boosted from in the frame
    // being boosted into.

    EvtVector4R vboost = vA + vB + vC;
    vboost.set( 1, -vboost.get( 1 ) );
    vboost.set( 2, -vboost.get( 2 ) );
    vboost.set( 3, -vboost.get( 3 ) );
    vA.applyBoostTo( vboost );
    vB.applyBoostTo( vboost );
    vC.applyBoostTo( vboost );

    // Rotate

    double alpha = EvtRandom::Flat( EvtConst::twoPi );
    double beta = acos( EvtRandom::Flat( -1.0, 1.0 ) );
    double gamma = EvtRandom::Flat( EvtConst::twoPi );

    vA.applyRotateEuler( alpha, beta, gamma );
    vB.applyRotateEuler( alpha, beta, gamma );
    vC.applyRotateEuler( alpha, beta, gamma );

    // Fill vector

    assert( v.size() == 0 );
    v.push_back( vA );
    v.push_back( vB );
    v.push_back( vC );

    return v;
}