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EvtHypNonLepton.cpp
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EvtHypNonLepton.cpp
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/***********************************************************************
* Copyright 1998-2020 CERN for the benefit of the EvtGen authors *
* *
* This file is part of EvtGen. *
* *
* EvtGen is free software: you can redistribute it and/or modify *
* it under the terms of the GNU General Public License as published by *
* the Free Software Foundation, either version 3 of the License, or *
* (at your option) any later version. *
* *
* EvtGen is distributed in the hope that it will be useful, *
* but WITHOUT ANY WARRANTY; without even the implied warranty of *
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the *
* GNU General Public License for more details. *
* *
* You should have received a copy of the GNU General Public License *
* along with EvtGen. If not, see <https://www.gnu.org/licenses/>. *
***********************************************************************/
#include "EvtGenModels/EvtHypNonLepton.hh"
#include "EvtGenBase/EvtComplex.hh"
#include "EvtGenBase/EvtDiracSpinor.hh"
#include "EvtGenBase/EvtGammaMatrix.hh"
#include "EvtGenBase/EvtPDL.hh"
#include "EvtGenBase/EvtParticle.hh"
#include "EvtGenBase/EvtTensor4C.hh"
#include "EvtGenBase/EvtVector4C.hh"
#include "EvtGenBase/EvtVector4R.hh"
EvtDecayBase* EvtHypNonLepton::clone()
{
return new EvtHypNonLepton;
}
std::string EvtHypNonLepton::getName()
{
return "HypNonLepton";
}
void EvtHypNonLepton::init()
{
if ( getNArg() < 2 || getNArg() > 3 ) { // alpha phi gamma delta
EvtGenReport( EVTGEN_ERROR, "EvtGen" )
<< " ERROR: EvtHypNonLepton generator expected 2 or 3 arguments but found: "
<< getNArg() << std::endl;
EvtGenReport( EVTGEN_INFO, "EvtGen" )
<< " 1. Decay asymmetry parameter - alpha" << std::endl;
EvtGenReport( EVTGEN_INFO, "EvtGen" )
<< " 2. Parameter phi - in degrees (not radians)" << std::endl;
EvtGenReport( EVTGEN_INFO, "EvtGen" )
<< " 3. Note on every x-th decay" << std::endl;
::abort();
}
if ( getNDaug() != 2 ) { // Check that there are 2 daughters only
EvtGenReport( EVTGEN_ERROR, "EvtGen" )
<< " ERROR: EvtHypNonLepton generator expected 2 daughters but found: "
<< getNDaug() << std::endl;
::abort();
}
// Check particles spins
if ( EvtSpinType::getSpin2( EvtPDL::getSpinType( getParentId() ) ) != 1 ) {
EvtGenReport( EVTGEN_ERROR, "EvtGen" )
<< " ERROR: EvtHypNonLepton generator expected dirac parent particle, but found "
<< EvtSpinType::getSpin2( EvtPDL::getSpinType( getParentId() ) )
<< " spin degrees of freedom" << std::endl;
::abort();
}
if ( EvtSpinType::getSpin2( EvtPDL::getSpinType( getDaug( 0 ) ) ) != 1 ) {
EvtGenReport( EVTGEN_ERROR, "EvtGen" )
<< " ERROR: EvtHypNonLepton generator expected the first child to be dirac particle, but found "
<< EvtSpinType::getSpin2( EvtPDL::getSpinType( getDaug( 0 ) ) )
<< " spin degrees of freedom" << std::endl;
::abort();
}
if ( EvtSpinType::getSpin2( EvtPDL::getSpinType( getDaug( 1 ) ) ) != 0 ) {
EvtGenReport( EVTGEN_ERROR, "EvtGen" )
<< " ERROR: EvtHypNonLepton generator expected the second child to be scalar particle, but found "
<< EvtSpinType::getSpin2( EvtPDL::getSpinType( getDaug( 1 ) ) )
<< " spin degrees of freedom" << std::endl;
::abort();
}
// Read all parameters
m_alpha = getArg( 0 );
m_phi = getArg( 1 ) * EvtConst::pi / 180;
if ( getNArg() == 3 )
m_noTries = static_cast<long>( getArg( 2 ) );
else
m_noTries = 0;
// calculate additional parameters
double p, M, m1, m2;
double p_to_s, beta, delta, gamma;
M = EvtPDL::getMass( getParentId() );
m1 = EvtPDL::getMass( getDaug( 0 ) );
m2 = EvtPDL::getMass( getDaug( 1 ) );
if ( m1 + m2 >= M ) {
EvtGenReport( EVTGEN_ERROR, "EvtGen" )
<< " ERROR: EvtHypNonLepton found impossible decay: " << M
<< " --> " << m1 << " + " << m2 << " GeV\n"
<< std::endl;
::abort();
}
p = sqrt( M * M - ( m1 + m2 ) * ( m1 + m2 ) ) *
sqrt( M * M - ( m1 - m2 ) * ( m1 - m2 ) ) / 2. / M;
beta = sqrt( 1. - m_alpha * m_alpha ) * sin( m_phi );
delta = -atan2( beta, m_alpha );
gamma = sqrt( 1. - m_alpha * m_alpha - beta * beta );
p_to_s = sqrt( ( 1. - gamma ) / ( 1. + gamma ) );
m_B_to_A = p_to_s * ( m1 + sqrt( p * p + m1 * m1 ) ) / p *
EvtComplex( cos( delta ), sin( delta ) );
}
void EvtHypNonLepton::initProbMax()
{
double maxProb, m1, m2, M, p;
M = EvtPDL::getMass( getParentId() );
m1 = EvtPDL::getMass( getDaug( 0 ) );
m2 = EvtPDL::getMass( getDaug( 1 ) );
if ( m1 + m2 >= M ) {
EvtGenReport( EVTGEN_ERROR, "EvtGen" )
<< " ERROR: EvtHypNonLepton found impossible decay: " << M
<< " --> " << m1 << " + " << m2 << " GeV\n"
<< std::endl;
::abort();
}
p = sqrt( M * M - ( m1 + m2 ) * ( m1 + m2 ) ) *
sqrt( M * M - ( m1 - m2 ) * ( m1 - m2 ) ) / 2 / M;
maxProb = 16 * M *
( sqrt( p * p + m1 * m1 ) + m1 +
abs( m_B_to_A ) * abs( m_B_to_A ) *
( sqrt( p * p + m1 * m1 ) - m1 ) );
//maxProb *= G_F*M_pi*M_pi;
setProbMax( maxProb );
EvtGenReport( EVTGEN_INFO, "EvtGen" )
<< " EvtHypNonLepton set up maximum probability to " << maxProb
<< std::endl;
}
void EvtHypNonLepton::decay( EvtParticle* parent )
{
parent->initializePhaseSpace( getNDaug(), getDaugs() );
calcAmp( &_amp2, parent );
}
void EvtHypNonLepton::calcAmp( EvtAmp* amp, EvtParticle* parent )
{
static long noTries = 0;
int i;
EvtComplex Matrix[2][2];
//G_F = 1.16637e-5;
//M_pi = 0.13957;
for ( i = 0; i < 4; i++ ) {
//std::cout << "--------------------------------------------------" << std::endl;
Matrix[i / 2][i % 2] = EvtLeptonSCurrent(
parent->sp( i / 2 ), parent->getDaug( 0 )->spParent( i % 2 ) );
//std::cout << "Matrix = " << Matrix[i/2][i%2] << std::endl;
Matrix[i / 2][i % 2] -=
m_B_to_A *
EvtLeptonPCurrent( parent->sp( i / 2 ),
parent->getDaug( 0 )->spParent( i % 2 ) );
//std::cout << "Matrix = " << Matrix[i/2][i%2] << std::endl;
//Matrix[i/2][i%2] *= G_F*M_pi*M_pi;
//std::cout << "Matrix = " << Matrix[i/2][i%2] << std::endl;
//std::cout << "--------------------------------------------------" << std::endl;
amp->vertex( i / 2, i % 2, Matrix[i / 2][i % 2] );
}
if ( m_noTries > 0 )
if ( !( ( ++noTries ) % m_noTries ) )
EvtGenReport( EVTGEN_DEBUG, "EvtGen" )
<< " EvtHypNonLepton already finished " << noTries
<< " matrix element calculations" << std::endl;
}

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