smash::DecayActionsFinder Class Reference

#include <decayactionsfinder.h>

A simple decay finder: Just loops through all particles and checks if they can decay during the next timestep.

Definition at line 25 of file decayactionsfinder.h.

Inheritance diagram for smash::DecayActionsFinder:

Collaboration diagram for smash::DecayActionsFinder:

Public Member Functions
	DecayActionsFinder ()
	Initialize the finder. More...
ActionList	find_actions_in_cell (const ParticleList &search_list, double dt, const double, const std::vector< FourVector > &) const override
	Check the whole particle list for decays. More...
ActionList	find_actions_with_neighbors (const ParticleList &, const ParticleList &, double, const std::vector< FourVector > &) const override
	Ignore the neighbor searches for decays. More...
ActionList	find_actions_with_surrounding_particles (const ParticleList &, const Particles &, double, const std::vector< FourVector > &) const override
	Ignore the surrounding searches for decays. More...
ActionList	find_final_actions (const Particles &search_list, bool only_res=false) const override
	Force all resonances to decay at the end of the simulation. More...
Public Member Functions inherited from smash::ActionFinderInterface
virtual	~ActionFinderInterface ()=default

Constructor & Destructor Documentation

smash::DecayActionsFinder::DecayActionsFinder ( )

inline

Initialize the finder.

Definition at line 28 of file decayactionsfinder.h.

{}

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Member Function Documentation

ActionList smash::DecayActionsFinder::find_actions_in_cell ( const ParticleList &  search_list, double  dt, const double  , const std::vector< FourVector > &    ) const

overridevirtual

Check the whole particle list for decays.

Parameters

[in]	search_list	All particles in grid cell.
[in]	dt	Size of timestep [fm]

Returns

List with the found (Decay)Action objects.

Implements smash::ActionFinderInterface.

Definition at line 22 of file decayactionsfinder.cc.

                                         {
  ActionList actions;
  /* for short time steps this seems reasonable to expect
   * less than 10 decays in most time steps */
  actions.reserve(10);

  for (const auto &p : search_list) {
    if (p.type().is_stable()) {
      continue;  // particle doesn't decay
    }

    DecayBranchList processes = p.type().get_partial_widths(
        p.momentum(), p.position().threevec(), WhichDecaymodes::Hadronic);
    // total decay width (mass-dependent)
    const double width = total_weight<DecayBranch>(processes);

    // check if there are any (hadronic) decays
    if (!(width > 0.0)) {
      continue;
    }

    constexpr double one_over_hbarc = 1. / hbarc;

    /* The decay_time is sampled from an exponential distribution.
     * Even though it may seem suspicious that it is sampled every
     * timestep, it can be proven that this still overall obeys
     * the exponential decay law.
     */
    double decay_time = random::exponential<double>(
        /* The clock goes slower in the rest
         * frame of the resonance */
        one_over_hbarc * p.inverse_gamma() * width);
    /* If the particle is not yet formed, shift the decay time by the time it
     * takes the particle to form */
    if (p.xsec_scaling_factor() < 1.0) {
      decay_time += p.formation_time() - p.position().x0();
    }
    if (decay_time < dt) {
      /* => decay_time ∈ [0, dt[
       * => the particle decays in this timestep. */
      auto act = make_unique<DecayAction>(p, decay_time);
      act->add_decays(std::move(processes));
      actions.emplace_back(std::move(act));
    }
  }
  return actions;
}

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ActionList smash::DecayActionsFinder::find_actions_with_neighbors ( const ParticleList &  , const ParticleList &  , double  , const std::vector< FourVector > &    ) const

inlineoverridevirtual

Ignore the neighbor searches for decays.

Implements smash::ActionFinderInterface.

Definition at line 42 of file decayactionsfinder.h.

                                                    {
    return {};
  }

ActionList smash::DecayActionsFinder::find_actions_with_surrounding_particles ( const ParticleList &  , const Particles &  , double  , const std::vector< FourVector > &    ) const

inlineoverridevirtual

Ignore the surrounding searches for decays.

Implements smash::ActionFinderInterface.

Definition at line 49 of file decayactionsfinder.h.

                                                    {
    return {};
  }

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ActionList smash::DecayActionsFinder::find_final_actions ( const Particles &  search_list, bool  only_res = false  ) const

overridevirtual

Force all resonances to decay at the end of the simulation.

Parameters

[in]	search_list	All particles at the end of simulation.
[in]	only_res	optional parameter that requests that only actions regarding resonances are considered (disregarding stable particles)

Returns

List with the found (Decay)Action objects.

Implements smash::ActionFinderInterface.

Definition at line 72 of file decayactionsfinder.cc.

                                                                {
  ActionList actions;

  for (const auto &p : search_list) {
    if (p.type().is_stable()) {
      continue;  // particle doesn't decay
    }
    auto act = make_unique<DecayAction>(p, 0.);
    act->add_decays(p.type().get_partial_widths(
        p.momentum(), p.position().threevec(), WhichDecaymodes::All));
    actions.emplace_back(std::move(act));
  }
  return actions;
}

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

• src/include/smash/decayactionsfinder.h
• src/decayactionsfinder.cc