EvtTensorParticle.cpp

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* Copyright 1998-2020 CERN for the benefit of the EvtGen authors       *
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* This file is part of EvtGen.                                         *
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#include "EvtGenBase/EvtTensorParticle.hh"

#include "EvtGenBase/EvtComplex.hh"
#include "EvtGenBase/EvtPatches.hh"
#include "EvtGenBase/EvtReport.hh"
#include "EvtGenBase/EvtTensor4C.hh"
#include "EvtGenBase/EvtVector4C.hh"
#include "EvtGenBase/EvtVector4R.hh"

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

void EvtTensorParticle::init( EvtId part_n, const EvtVector4R& p4 )
{
    init( part_n, p4.get( 0 ), p4.get( 1 ), p4.get( 2 ), p4.get( 3 ) );

    setLifetime();
}

void EvtTensorParticle::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].setdiag( 0.0, -1.0 / sqrt( 6.0 ), -1.0 / sqrt( 6.0 ),
                    2.0 / sqrt( 6.0 ) );
    eps[1].setdiag( 0.0, 1.0 / sqrt( 2.0 ), -1.0 / sqrt( 2.0 ), 0.0 );
    eps[2].setdiag( 0.0, 0.0, 0.0, 0.0 );
    eps[3].setdiag( 0.0, 0.0, 0.0, 0.0 );
    eps[4].setdiag( 0.0, 0.0, 0.0, 0.0 );

    eps[2].set( 1, 2, EvtComplex( 1.0 / sqrt( 2.0 ), 0.0 ) );
    eps[2].set( 2, 1, EvtComplex( 1.0 / sqrt( 2.0 ), 0.0 ) );
    eps[3].set( 1, 3, EvtComplex( 1.0 / sqrt( 2.0 ), 0.0 ) );
    eps[3].set( 3, 1, EvtComplex( 1.0 / sqrt( 2.0 ), 0.0 ) );
    eps[4].set( 2, 3, EvtComplex( 1.0 / sqrt( 2.0 ), 0.0 ) );
    eps[4].set( 3, 2, EvtComplex( 1.0 / sqrt( 2.0 ), 0.0 ) );

    setLifetime();
}

void EvtTensorParticle::init( EvtId part_n, const EvtVector4R& p4,
                              const EvtTensor4C& epsin1,
                              const EvtTensor4C& epsin2,
                              const EvtTensor4C& epsin3,
                              const EvtTensor4C& epsin4,
                              const EvtTensor4C& epsin5 )
{
    _validP4 = true;
    setp( p4 );
    setpart_num( part_n );

    eps[0] = epsin1;
    eps[1] = epsin2;
    eps[2] = epsin3;
    eps[3] = epsin4;
    eps[4] = epsin5;

    setLifetime();
}

EvtTensor4C EvtTensorParticle::epsTensorParent( int i ) const
{
    EvtTensor4C temp = eps[i];

    temp.applyBoostTo( this->getP4() );
    return temp;

}    //epsParent

EvtTensor4C EvtTensorParticle::epsTensor( int i ) const
{
    return eps[i];

}    //eps

EvtSpinDensity EvtTensorParticle::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 EvtTensor4C dPpp( EvtGenFunctions::directProd( eplus, eplus ) );
    static EvtTensor4C dPp0( EvtGenFunctions::directProd( eplus, ezero ) );
    static EvtTensor4C dP0p( EvtGenFunctions::directProd( ezero, eplus ) );
    static EvtTensor4C dPpm( EvtGenFunctions::directProd( eplus, eminus ) );
    static EvtTensor4C dP00( EvtGenFunctions::directProd( ezero, ezero ) );
    static EvtTensor4C dPmp( EvtGenFunctions::directProd( eminus, eplus ) );
    static EvtTensor4C dPmm( EvtGenFunctions::directProd( eminus, eminus ) );
    static EvtTensor4C dPm0( EvtGenFunctions::directProd( eminus, ezero ) );
    static EvtTensor4C dP0m( EvtGenFunctions::directProd( ezero, eminus ) );

    static EvtTensor4C es0( conj( dPpp ) );
    static EvtTensor4C es1(
        conj( ( 1 / sqrt( 2.0 ) ) * dPp0 + ( 1 / sqrt( 2.0 ) ) * dP0p ) );
    static EvtTensor4C es2( conj( ( 1 / sqrt( 6.0 ) ) * dPpm +
                                  ( 2 / sqrt( 6.0 ) ) * dP00 +
                                  ( 1 / sqrt( 6.0 ) ) * dPmp ) );
    static EvtTensor4C es3(
        conj( ( 1 / sqrt( 2.0 ) ) * dPm0 + ( 1 / sqrt( 2.0 ) ) * dP0m ) );
    static EvtTensor4C es4( conj( dPmm ) );

    EvtSpinDensity R;
    R.setDim( 5 );

    for ( int j = 0; j < 5; j++ ) {
        R.set( 0, j, cont( es0, eps[j] ) );
        R.set( 1, j, cont( es1, eps[j] ) );
        R.set( 2, j, cont( es2, eps[j] ) );
        R.set( 3, j, cont( es3, eps[j] ) );
        R.set( 4, j, cont( es4, eps[j] ) );
    }
    return R;
}

EvtSpinDensity EvtTensorParticle::rotateToHelicityBasis( double alpha,
                                                         double beta,
                                                         double gamma ) const
{
    EvtTensor4C es[5];

    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 );

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

    for ( int i = 0; i < 5; i++ )
        es[i].zero();

    es[0] = EvtGenFunctions::directProd( eplus, eplus );
    es[1] = ( 1 / sqrt( 2.0 ) ) * EvtGenFunctions::directProd( eplus, ezero ) +
            ( 1 / sqrt( 2.0 ) ) * EvtGenFunctions::directProd( ezero, eplus );
    es[2] = ( 1 / sqrt( 6.0 ) ) * EvtGenFunctions::directProd( eplus, eminus ) +
            ( 2 / sqrt( 6.0 ) ) * EvtGenFunctions::directProd( ezero, ezero ) +
            ( 1 / sqrt( 6.0 ) ) * EvtGenFunctions::directProd( eminus, eplus );
    es[3] = ( 1 / sqrt( 2.0 ) ) * EvtGenFunctions::directProd( eminus, ezero ) +
            ( 1 / sqrt( 2.0 ) ) * EvtGenFunctions::directProd( ezero, eminus );
    es[4] = EvtGenFunctions::directProd( eminus, eminus );

    for ( int i = 0; i < 5; i++ )
        es[i] = conj( es[i] );

    EvtSpinDensity R;
    R.setDim( 5 );

    for ( int i = 0; i < 5; i++ )
        for ( int j = 0; j < 5; j++ )
            R.set( i, j, cont( es[i], eps[j] ) );

    return R;
}