marley::FragmentDiscreteExitChannel Class Reference

Fragment emission ExitChannel that leads to a discrete nuclear level in the final state More...

#include <ExitChannel.hh>

Inheritance diagram for marley::FragmentDiscreteExitChannel:

Public Member Functions
	FragmentDiscreteExitChannel (int pdgi, int qi, double Exi, int twoJi, marley::Parity Pi, double rho_i, marley::StructureDatabase &sdb, const marley::Level &flev, const marley::Fragment &frag)
virtual void	compute_total_width () final override
Public Member Functions inherited from marley::DiscreteExitChannel
	DiscreteExitChannel (const marley::Level &flev)
virtual void	do_decay (double &Ex, int &two_J, marley::Parity &Pi, const std::shared_ptr< HepMC3::GenParticle > &compound_nucleus, std::shared_ptr< HepMC3::GenParticle > &emitted_particle, std::shared_ptr< HepMC3::GenParticle > &residual_nucleus, int &qIon, marley::Generator &gen) const final override
	Simulates a nuclear decay into this channel.
const marley::Level &	get_final_level () const
	Get a const reference to the final-state nuclear level.
virtual bool	is_continuum () const final override
	Returns true if this channel accesses the particle-unbound continuum of nuclear levels or false otherwise.
Public Member Functions inherited from marley::ExitChannel
	ExitChannel ()=default
	ExitChannel (int pdgi, int qi, double Exi, int twoJi, marley::Parity Pi, double rho_i, marley::StructureDatabase &sdb)
double	width () const
	Get the total decay width into this channel (MeV)
Public Member Functions inherited from marley::FragmentExitChannel
	FragmentExitChannel (const marley::Fragment &fragment)
virtual bool	emits_fragment () const final override
	Returns true if this channel involves fragment emission or false if it involves gamma-ray emission.
virtual int	emitted_particle_pdg () const final override
	Returns the PDG code for the particle (gamma-ray or nuclear fragment) emitted by decays into this ExitChannel.
virtual int	final_nucleus_pdg () const final override
	Returns the PDG code for the final nucleus.

Additional Inherited Members
Static Public Member Functions inherited from marley::ExitChannel
template<typename It>
static marley::IteratorToPointerMember< It, double >	make_width_iterator (It it)
	Convert an iterator that points to an ExitChannel object into an iterator to the ExitChannel's width_ member variable.
Protected Member Functions inherited from marley::ExitChannel
virtual void	prepare_products (const std::shared_ptr< HepMC3::GenParticle > &compound_nucleus, std::shared_ptr< HepMC3::GenParticle > &emitted_particle, std::shared_ptr< HepMC3::GenParticle > &residual_nucleus, double Exf, int &qf, marley::Generator &gen) const
	Helper function that prepares Particle objects representing the products of the two-body decay.
Protected Member Functions inherited from marley::FragmentExitChannel
double	max_Exf () const
	Helper function that returns that maximum possible excitation energy for the daughter nucleus after emission of the fragment.
Protected Attributes inherited from marley::DiscreteExitChannel
const marley::Level &	final_level_
	Reference to the final-state nuclear level.
Protected Attributes inherited from marley::ExitChannel
double	Exi_
	Initial nuclear excitation energy \( E_x \) (MeV)
double	one_over_two_pi_rho_i_
int	pdgi_
	PDG code for the initial nucleus.
marley::Parity	Pi_
	Initial nuclear parity \( \Pi \).
int	qi_
marley::StructureDatabase *	sdb_
	StructureDatabase to use in calculations.
int	twoJi_
	Two times the initial nuclear spin \( J \).
double	width_
	Total decay width into this channel (MeV)
Protected Attributes inherited from marley::FragmentExitChannel
int	fragment_pdg_
	PDG code identifying the emitted fragment.

Detailed Description

Fragment emission ExitChannel that leads to a discrete nuclear level in the final state

Definition at line 359 of file ExitChannel.hh.

Constructor & Destructor Documentation

FragmentDiscreteExitChannel()

marley::FragmentDiscreteExitChannel::FragmentDiscreteExitChannel ( int pdgi, int qi, double Exi, int twoJi, marley::Parity Pi, double rho_i, marley::StructureDatabase & sdb, const marley::Level & flev, const marley::Fragment & frag )

inline

Note

This line keeps old versions (4.9.3) of GCC happy

Definition at line 367 of file ExitChannel.hh.

        : ExitChannel( pdgi, qi, Exi, twoJi, Pi, rho_i, sdb ),
        DiscreteExitChannel( flev ), FragmentExitChannel( frag )
      {
        this->compute_total_width();
      }

References marley::DiscreteExitChannel::DiscreteExitChannel(), marley::FragmentExitChannel::FragmentExitChannel(), and compute_total_width().

Member Function Documentation

compute_total_width()

void marley::FragmentDiscreteExitChannel::compute_total_width ( )

finaloverridevirtual

Helper function that initializes the width_ member variable upon construction

Implements marley::ExitChannel.

Definition at line 85 of file ExitChannel.cc.

                                                            {
 
  int remnant_pdg = this->final_nucleus_pdg();
  marley::OpticalModel& om = sdb_->get_optical_model( remnant_pdg );
 
  // Get information about the emitted fragment
  const marley::Fragment& f = *sdb_->get_fragment( fragment_pdg_ );
 
  int two_s = f.get_two_s(); // two times the fragment spin
  marley::Parity Pa = f.get_parity(); // intrinsic parity
 
  // Maximum possible excitation energy in the daughter nucleus after the
  // fragment is emitted
  double Exf_max = this->max_Exf();
 
  // Excitation energy of the final nuclear level
  double Exf = final_level_.energy();
 
  // Initialize the total decay width to zero, just in case
  width_ = 0.;
 
  if ( Exf >= Exf_max ) {
    issue_Exf_warning( Exf, Exf_max );
    return;
  }
 
  // Total kinetic energy in the CM frame immediately after the binary decay
  double total_KE_CM_frame = Exf_max - Exf;
 
  int twoJf = final_level_.twoJ();
  marley::Parity Pf = final_level_.parity();
 
  for (int two_j = std::abs(twoJi_ - twoJf); two_j <= twoJi_ + twoJf;
    two_j += 2)
  {
    int j_plus_s = (two_j + two_s) / 2;
 
    // For each new iteration, increment l and flip the overall final
    // state parity
    int l = std::abs(two_j - two_s) / 2;
    bool l_is_odd = l % 2;
    marley::Parity P_final_state = Pf * Pa * marley::Parity( !l_is_odd );
    for ( ; l <= j_plus_s; ++l, !P_final_state )
    {
      // The current term in the sum only contributes to the total decay
      // width if parity is conserved
      if ( Pi_ == P_final_state ) {
 
        double Tlj = om.transmission_coefficient( total_KE_CM_frame,
          fragment_pdg_, two_j, l, two_s );
 
        double partial_width = one_over_two_pi_rho_i_ * Tlj;
 
        width_ += partial_width;
 
        // TODO: cache term indexed by l, two_j
      }
    }
  }
 
  // Guard against numerical issues by capping the total width at zero
  width_ = std::max( 0., width_ );
}

References marley::DiscreteExitChannel::final_level_, marley::FragmentExitChannel::final_nucleus_pdg(), marley::FragmentExitChannel::fragment_pdg_, marley::Fragment::get_parity(), marley::Fragment::get_two_s(), marley::FragmentExitChannel::max_Exf(), marley::ExitChannel::one_over_two_pi_rho_i_, marley::ExitChannel::Pi_, marley::ExitChannel::sdb_, marley::OpticalModel::transmission_coefficient(), marley::ExitChannel::twoJi_, and marley::ExitChannel::width_.

Referenced by FragmentDiscreteExitChannel().

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

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