EvtVectorParticle.cpp

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* Copyright 1998-2020 CERN for the benefit of the EvtGen authors       *
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#include "EvtGenBase/EvtVectorParticle.hh"

#include "EvtGenBase/EvtComplex.hh"
#include "EvtGenBase/EvtPDL.hh"
#include "EvtGenBase/EvtPatches.hh"
#include "EvtGenBase/EvtReport.hh"
#include "EvtGenBase/EvtVector4C.hh"

#include <iostream>
#include <math.h>
#include <stdlib.h>

void EvtVectorParticle::init( EvtId part_n, double e, double px, double py,
                              double pz )
{
    _validP4 = true;
    setp( e, px, py, pz );
    setpart_num( part_n );

    _eps[0].set( 0.0, 1.0, 0.0, 0.0 );
    _eps[1].set( 0.0, 0.0, 1.0, 0.0 );
    _eps[2].set( 0.0, 0.0, 0.0, 1.0 );

    setLifetime();
}

void EvtVectorParticle::init( EvtId part_n, const EvtVector4R& p4 )
{
    _validP4 = true;
    setp( p4 );
    setpart_num( part_n );

    _eps[0].set( 0.0, 1.0, 0.0, 0.0 );
    _eps[1].set( 0.0, 0.0, 1.0, 0.0 );
    _eps[2].set( 0.0, 0.0, 0.0, 1.0 );
    setLifetime();
}

void EvtVectorParticle::init( EvtId part_n, const EvtVector4R& p4,
                              const EvtVector4C& epsin1,
                              const EvtVector4C& epsin2,
                              const EvtVector4C& epsin3 )
{
    _validP4 = true;
    setp( p4 );
    setpart_num( part_n );

    _eps[0] = epsin1;
    _eps[1] = epsin2;
    _eps[2] = epsin3;

    setLifetime();
}

EvtSpinDensity EvtVectorParticle::rotateToHelicityBasis() const
{
    static EvtVector4C eplus( 0.0, -1.0 / sqrt( 2.0 ),
                              EvtComplex( 0.0, -1.0 / sqrt( 2.0 ) ), 0.0 );
    static EvtVector4C ezero( 0.0, 0.0, 0.0, 1.0 );
    static EvtVector4C eminus( 0.0, 1.0 / sqrt( 2.0 ),
                               EvtComplex( 0.0, -1.0 / sqrt( 2.0 ) ), 0.0 );

    static EvtVector4C eplusC( eplus.conj() );
    static EvtVector4C ezeroC( ezero.conj() );
    static EvtVector4C eminusC( eminus.conj() );

    EvtSpinDensity R;
    R.setDim( 3 );

    for ( int i = 0; i < 3; i++ ) {
        R.set( 0, i, (eplusC)*_eps[i] );
        R.set( 1, i, (ezeroC)*_eps[i] );
        R.set( 2, i, (eminusC)*_eps[i] );
    }

    return R;
}

EvtSpinDensity EvtVectorParticle::rotateToHelicityBasis( double alpha,
                                                         double beta,
                                                         double gamma ) const
{
    EvtVector4C eplus( 0.0, -1.0 / sqrt( 2.0 ),
                       EvtComplex( 0.0, -1.0 / sqrt( 2.0 ) ), 0.0 );
    EvtVector4C ezero( 0.0, 0.0, 0.0, 1.0 );
    EvtVector4C eminus( 0.0, 1.0 / sqrt( 2.0 ),
                        EvtComplex( 0.0, -1.0 / sqrt( 2.0 ) ), 0.0 );

    eplus.applyRotateEuler( alpha, beta, gamma );
    ezero.applyRotateEuler( alpha, beta, gamma );
    eminus.applyRotateEuler( alpha, beta, gamma );

    EvtSpinDensity R;
    R.setDim( 3 );

    for ( int i = 0; i < 3; i++ ) {
        R.set( 0, i, ( eplus.conj() ) * _eps[i] );
        R.set( 1, i, ( ezero.conj() ) * _eps[i] );
        R.set( 2, i, ( eminus.conj() ) * _eps[i] );
    }

    return R;
}