marley::HauserFeshbachDecay Class Reference

Monte Carlo implementation of the Hauser-Feshbach statistical model for decays of highly-excited nuclei. More...

#include <HauserFeshbachDecay.hh>

Public Member Functions
	HauserFeshbachDecay (const std::shared_ptr< HepMC3::GenParticle > &compound_nucleus, double Exi, int twoJi, marley::Parity Pi, marley::StructureDatabase &sdb)
const marley::ExitChannel &	do_decay (double &Exf, int &twoJf, marley::Parity &Pf, std::shared_ptr< HepMC3::GenParticle > &emitted_particle, std::shared_ptr< HepMC3::GenParticle > &residual_nucleus, int &qIon, marley::Generator &gen)
	Simulates a decay of the compound nucleus.
std::vector< std::unique_ptr< marley::ExitChannel > > &	exit_channels ()
	Get a non-const reference to the owned vector of ExitChannel pointers.
const std::vector< std::unique_ptr< marley::ExitChannel > > &	exit_channels () const
	Get a const reference to the owned vector of ExitChannel pointers.
void	print (std::ostream &out) const
	Print information about the possible decay channels to a std::ostream.
const std::unique_ptr< marley::ExitChannel > &	sample_exit_channel (marley::Generator &gen) const
	Helper function for do_decay(). Samples an ExitChannel using the partial decay widths as weights.
double	total_width () const

Detailed Description

Monte Carlo implementation of the Hauser-Feshbach statistical model for decays of highly-excited nuclei.

Definition at line 34 of file HauserFeshbachDecay.hh.

Constructor & Destructor Documentation

HauserFeshbachDecay()

marley::HauserFeshbachDecay::HauserFeshbachDecay	(	const std::shared_ptr< HepMC3::GenParticle > &	compound_nucleus,
		double	Exi,
		int	twoJi,
		marley::Parity	Pi,
		marley::StructureDatabase &	sdb )

Parameters

compound_nucleus	GenParticle object that represents the excited nucleus
Exi	Initial excitation energy (MeV)
twoJi	Two times the initial nuclear spin
Pi	Initial nuclear parity
sdb	Reference to the StructureDatabase to use in calculations

Definition at line 28 of file HauserFeshbachDecay.cc.

                                 : compound_nucleus_( compound_nucleus ),
  Exi_( Exi ), twoJi_( twoJi ), Pi_( Pi )
{
  build_exit_channels( sdb );
}

Member Function Documentation

do_decay()

const marley::ExitChannel & marley::HauserFeshbachDecay::do_decay	(	double &	Exf,
		int &	twoJf,
		marley::Parity &	Pf,
		std::shared_ptr< HepMC3::GenParticle > &	emitted_particle,
		std::shared_ptr< HepMC3::GenParticle > &	residual_nucleus,
		int &	qIon,
		marley::Generator &	gen )

Simulates a decay of the compound nucleus.

Parameters

[out]	Exf	Final nuclear excitation energy (MeV)
[out]	twoJf	Two times the final nuclear spin
[out]	Pf	Final nuclear parity
[out]	emitted_particle	GenParticle object representing the nuclear fragment or γ-ray emitted during the decay
[out]	residual_nucleus	GenParticle object representing the final-state nucleus (ion)
[out]	qIon	Charge (in units of the elementary charge) of the residual nucleus (ion)
	gen	Generator to use for random sampling

Returns

The ExitChannel object that was chosen while simulating the decay

Definition at line 229 of file HauserFeshbachDecay.cc.

{
  const auto& ec = this->sample_exit_channel( gen );
 
  ec->do_decay( Exf, twoJf, Pf, compound_nucleus_, emitted_particle,
    residual_nucleus, qIon, gen );
 
  return *ec;
}

References sample_exit_channel().

Referenced by marley::NucleusDecayer::process_event().

exit_channels() [1/2]

std::vector< std::unique_ptr< marley::ExitChannel > > & marley::HauserFeshbachDecay::exit_channels ( )

inline

Get a non-const reference to the owned vector of ExitChannel pointers.

Definition at line 110 of file HauserFeshbachDecay.hh.

{ return exit_channels_; }

Referenced by marley::OMPWeightCalculator::weight().

exit_channels() [2/2]

const std::vector< std::unique_ptr< marley::ExitChannel > > & marley::HauserFeshbachDecay::exit_channels ( ) const

inline

Get a const reference to the owned vector of ExitChannel pointers.

Definition at line 113 of file HauserFeshbachDecay.hh.

{ return exit_channels_; }

print()

void marley::HauserFeshbachDecay::print

(

std::ostream &

out

)

const

Print information about the possible decay channels to a std::ostream.

Definition at line 243 of file HauserFeshbachDecay.cc.

                                                           {
 
  out << "Compound nucleus " << compound_nucleus_->pid()
    << " with Ex = " << Exi_ << ", spin = " << twoJi_ / 2;
  if (twoJi_ % 2) out << ".5";
  out << ", and parity = " << Pi_ << '\n';
  out << "Total width = " << total_width_ << " MeV\n";
  out << "Mean lifetime = " << marley_utils::hbar / total_width_ << " s\n";
  for (const auto& ec : exit_channels_) {
    double width = ec->width();
    bool continuum = ec->is_continuum();
    bool frag = ec->emits_fragment();
    int pdg = ec->emitted_particle_pdg();
    std::string symbol = marley_utils::particle_symbols.at( pdg );
    out << "  ";
    if ( frag ) out << symbol;
    else out << "gamma-ray";
    if ( continuum ) out << " emission to the continuum width = ";
    else {
      auto* dec = dynamic_cast< marley::DiscreteExitChannel* >( ec.get() );
      if ( !dec ) throw marley::Error( "Dynamic cast failed in marley::"
        "HauserFeshbachDecay::print()" );
      out << " emission to level at " << dec->get_final_level().energy()
        << " MeV width = ";
    }
    out << width << " MeV\n";
  }
}

sample_exit_channel()

const std::unique_ptr< marley::ExitChannel > & marley::HauserFeshbachDecay::sample_exit_channel

(

marley::Generator &

gen

)

const

Helper function for do_decay(). Samples an ExitChannel using the partial decay widths as weights.

Definition at line 273 of file HauserFeshbachDecay.cc.

{
  // Throw an error if all decays are impossible
  if ( total_width_ <= 0. ) throw marley::Error( "Cannot sample an exit channel"
    " for a Hauser-Feshbach decay. All partial decay widths are zero." );
 
  // Sample an exit channel using a std::discrete distribution and a table of
  // partial decay widths
  const auto widths_begin
    = marley::ExitChannel::make_width_iterator( exit_channels_.cbegin() );
  const auto widths_end
    = marley::ExitChannel::make_width_iterator( exit_channels_.cend() );
 
  std::discrete_distribution<size_t> exit_channel_dist( widths_begin,
    widths_end );
  size_t exit_channel_index = gen.sample_from_distribution( exit_channel_dist );
 
  const auto& ec = exit_channels_.at( exit_channel_index );
 
  // Log which exit channel was selected and its branching fraction
  double width_ec = ec->width();
  double branching = ( total_width_ > 0. ) ? ( width_ec / total_width_ ) : 0.;
  int ec_pdg = ec->emitted_particle_pdg();
  std::string ec_symbol = marley_utils::particle_symbols.count( ec_pdg )
    ? marley_utils::particle_symbols.at( ec_pdg ) : std::to_string( ec_pdg );
  MARLEY_LOG( DEBUG, "physics.deexcitation.hauser" ) << "Selected exit channel:"
    " emits " << ec_symbol
    << ( ec->is_continuum() ? " to continuum" : " to discrete level" )
    << ", width = " << width_ec << " MeV"
    << ", branching fraction = " << branching;
 
  return ec;
}

References marley::ExitChannel::make_width_iterator(), and marley::Generator::sample_from_distribution().

Referenced by do_decay().

total_width()

double marley::HauserFeshbachDecay::total_width ( ) const

inline

Definition at line 115 of file HauserFeshbachDecay.hh.

    { return total_width_; }

---

The documentation for this class was generated from the following files:

• /home/sjg/Desktop/marley/include/marley/HauserFeshbachDecay.hh
• /home/sjg/Desktop/marley/src/HauserFeshbachDecay.cc