smash::SphereModus Class Reference

#include <spheremodus.h>

SphereModus: Provides a modus for expanding matter calculations

Matter is put in a sphere of radius R with uniform density; isotropic thermal momenta are typically used for initialization, although other initial momentum states are also included, see Bazow:2016oky [6] and Tindall:2016try [49]

To use this modus, choose

General:
     Modus: Sphere

in the configuration file.

Options for SphereModus go in the "Modi"→"Sphere" section of the configuration:

Modi:
     Sphere:
             # definitions here

The following configuration options are understood: Sphere

Definition at line 47 of file spheremodus.h.

Inheritance diagram for smash::SphereModus:

Collaboration diagram for smash::SphereModus:

Public Member Functions
	SphereModus (Configuration modus_config, const ExperimentParameters &parameters)
	Constructor. More...
double	initial_conditions (Particles *particles, const ExperimentParameters &parameters)
	Generates initial state of the particles in the system according to specified parameters: number of particles of each species, momentum and coordinate space distributions. More...
Public Member Functions inherited from smash::ModusDefault
int	impose_boundary_conditions (Particles *, const OutputsList &={})
	Enforces sensible positions for the particles. More...
int	total_N_number () const
int	proj_N_number () const
bool	cll_in_nucleus () const
bool	is_collider () const
bool	is_box () const
bool	is_list () const
double	sqrt_s_NN () const
double	impact_parameter () const
double	velocity_projectile () const
double	velocity_target () const
FermiMotion	fermi_motion () const
double	max_timestep (double) const
double	equilibration_time () const
double	nuclei_passing_time () const
	Get the passing time of the two nuclei in a collision. More...
Grid< GridOptions::Normal >	create_grid (const Particles &particles, double min_cell_length, double timestep_duration, CellSizeStrategy strategy=CellSizeStrategy::Optimal) const
	Creates the Grid with normal boundary conditions. More...

Private Attributes
double	radius_
	Sphere radius (in fm/c) More...
double	sphere_temperature_
	Temperature for momentum distribution (in GeV) More...
const double	start_time_ = 0.
	Starting time for the Sphere. More...
const bool	use_thermal_ = false
	Whether to use a thermal initialization for all particles instead of specific numbers. More...
const double	mub_
	Baryon chemical potential for thermal initialization; only used if use_thermal_ is true. More...
const double	mus_
	Strange chemical potential for thermal initialization; only used if use_thermal_ is true. More...
const bool	account_for_resonance_widths_
	In case of thermal initialization: true – account for resonance spectral functions, while computing multiplicities and sampling masses, false – simply use pole masses. More...
const std::map< PdgCode, int >	init_multipl_
	Particle multiplicities at initialization; required if use_thermal_ is false. More...
std::map< PdgCode, double >	average_multipl_
	Average multiplicities in case of thermal initialization. More...
const SphereInitialCondition	init_distr_
	Initialization scheme for momenta in the sphere; used for expanding metric setup. More...
const bool	insert_jet_ = false
	Whether to insert a single high energy particle at the center of the expanding sphere (0,0,0). More...
const PdgCode	jet_pdg_
	Pdg of the particle to use as a jet; necessary if insert_jet_ is true, unused otherwise. More...
const double	jet_mom_
	Initial momentum of the jet particle; only used if insert_jet_ is true. More...

Friends
std::ostream &	operator<< (std::ostream &, const SphereModus &)

Constructor & Destructor Documentation

SphereModus()

smash::SphereModus::SphereModus ( Configuration  modus_config, const ExperimentParameters &  parameters  )

explicit

Constructor.

Takes all there is to take from the (truncated!) configuration object (only contains configuration for this modus).

Parameters

[in]	modus_config	The configuration object that sets all initial conditions of the experiment.
[in]	parameters	Unused, but necessary because of templated initialization

Definition at line 164 of file spheremodus.cc.

    : radius_(modus_config.take({"Sphere", "Radius"})),
      sphere_temperature_(modus_config.take({"Sphere", "Temperature"})),
      start_time_(modus_config.take({"Sphere", "Start_Time"}, 0.)),
      use_thermal_(
          modus_config.take({"Sphere", "Use_Thermal_Multiplicities"}, false)),
      mub_(modus_config.take({"Sphere", "Baryon_Chemical_Potential"}, 0.)),
      mus_(modus_config.take({"Sphere", "Strange_Chemical_Potential"}, 0.)),
      account_for_resonance_widths_(
          modus_config.take({"Sphere", "Account_Resonance_Widths"}, true)),
      init_multipl_(use_thermal_
                        ? std::map<PdgCode, int>()
                        : modus_config.take({"Sphere", "Init_Multiplicities"})
                              .convert_for(init_multipl_)),
      init_distr_(
          modus_config.take({"Sphere", "Initial_Condition"},
                            SphereInitialCondition::ThermalMomentaBoltzmann)),
      insert_jet_(modus_config.has_value({"Sphere", "Jet", "Jet_PDG"})),
      jet_pdg_(insert_jet_ ? modus_config.take({"Sphere", "Jet", "Jet_PDG"})
                                 .convert_for(jet_pdg_)
                           : pdg::p),  // dummy default; never used
      jet_mom_(modus_config.take({"Sphere", "Jet", "Jet_Momentum"}, 20.)) {}

Member Function Documentation

initial_conditions()

double smash::SphereModus::initial_conditions	(	Particles *	particles,
		const ExperimentParameters &	parameters
	)

Generates initial state of the particles in the system according to specified parameters: number of particles of each species, momentum and coordinate space distributions.

Susbsequently makes the total 3-momentum 0.

Parameters

[out]	particles	An empty list that gets filled up by this function
[in]	parameters	The initialization parameters of the box

Returns

The starting time of the simulation

Definition at line 231 of file spheremodus.cc.

                                                                               {
  FourVector momentum_total(0, 0, 0, 0);
  const double T = this->sphere_temperature_;
  const double V = 4.0 / 3.0 * M_PI * radius_ * radius_ * radius_;
  /* Create NUMBER OF PARTICLES according to configuration */
  if (use_thermal_) {
    if (average_multipl_.empty()) {
      for (const ParticleType &ptype : ParticleType::list_all()) {
        if (HadronGasEos::is_eos_particle(ptype)) {
          const double n = HadronGasEos::partial_density(
              ptype, T, mub_, mus_, account_for_resonance_widths_);
          average_multipl_[ptype.pdgcode()] = n * V * parameters.testparticles;
        }
      }
    }
    double nb_init = 0.0, ns_init = 0.0;
    for (const auto &mult : average_multipl_) {
      const int thermal_mult_int = random::poisson(mult.second);
      particles->create(thermal_mult_int, mult.first);
      nb_init += mult.second * mult.first.baryon_number();
      ns_init += mult.second * mult.first.strangeness();
      logg[LSphere].debug(mult.first, " initial multiplicity ",
                          thermal_mult_int);
    }
    logg[LSphere].info("Initial hadron gas baryon density ", nb_init);
    logg[LSphere].info("Initial hadron gas strange density ", ns_init);
  } else {
    for (const auto &p : init_multipl_) {
      particles->create(p.second * parameters.testparticles, p.first);
      logg[LSphere].debug("Particle ", p.first, " initial multiplicity ",
                          p.second);
    }
  }
  std::unique_ptr<QuantumSampling> quantum_sampling;
  if (this->init_distr_ == SphereInitialCondition::ThermalMomentaQuantum) {
    quantum_sampling = make_unique<QuantumSampling>(init_multipl_, V, T);
  }
  /* loop over particle data to fill in momentum and position information */
  for (ParticleData &data : *particles) {
    Angles phitheta;
    /* thermal momentum according Maxwell-Boltzmann distribution */
    double momentum_radial = 0.0, mass = data.pole_mass();
    /* assign momentum_radial according to requested distribution */
    switch (init_distr_) {
      case (SphereInitialCondition::IC_ES):
        momentum_radial = sample_momenta_IC_ES(T);
        break;
      case (SphereInitialCondition::IC_1M):
        momentum_radial = sample_momenta_1M_IC(T, mass);
        break;
      case (SphereInitialCondition::IC_2M):
        momentum_radial = sample_momenta_2M_IC(T, mass);
        break;
      case (SphereInitialCondition::IC_Massive):
        momentum_radial = sample_momenta_non_eq_mass(T, mass);
        break;
      case (SphereInitialCondition::ThermalMomentaBoltzmann):
      default:
        mass = (!account_for_resonance_widths_)
                   ? data.type().mass()
                   : HadronGasEos::sample_mass_thermal(data.type(), 1.0 / T);
        momentum_radial = sample_momenta_from_thermal(T, mass);
        break;
      case (SphereInitialCondition::ThermalMomentaQuantum):
        /*
         * **********************************************************************
         * Sampling the thermal momentum according Bose/Fermi/Boltzmann
         * distribution.
         * We take the pole mass as the mass.
         * **********************************************************************
         */
        mass = data.type().mass();
        momentum_radial = quantum_sampling->sample(data.pdgcode());
        break;
    }
    phitheta.distribute_isotropically();
    logg[LSphere].debug(data.type().name(), "(id ", data.id(),
                        ") radial momentum ", momentum_radial, ", direction",
                        phitheta);
    data.set_4momentum(mass, phitheta.threevec() * momentum_radial);
    momentum_total += data.momentum();
    /* uniform sampling in a sphere with radius r */
    double position_radial;
    position_radial = std::cbrt(random::canonical()) * radius_;
    Angles pos_phitheta;
    pos_phitheta.distribute_isotropically();
    data.set_4position(
        FourVector(start_time_, pos_phitheta.threevec() * position_radial));
    data.set_formation_time(start_time_);
  }
  /* Make total 3-momentum 0 */
  for (ParticleData &data : *particles) {
    data.set_4momentum(data.momentum().abs(),
                       data.momentum().threevec() -
                           momentum_total.threevec() / particles->size());
  }
 
  /* Add a single highly energetic particle in the center of the sphere (jet) */
  if (insert_jet_) {
    auto &jet_particle = particles->create(jet_pdg_);
    jet_particle.set_formation_time(start_time_);
    jet_particle.set_4position(FourVector(start_time_, 0., 0., 0.));
    jet_particle.set_4momentum(ParticleType::find(jet_pdg_).mass(),
                               ThreeVector(jet_mom_, 0., 0.));
  }
 
  /* Recalculate total momentum */
  momentum_total = FourVector(0, 0, 0, 0);
  for (ParticleData &data : *particles) {
    momentum_total += data.momentum();
    /* IC: debug checks */
    logg[LSphere].debug() << data;
  }
  /* allows to check energy conservation */
  logg[LSphere].debug() << "Sphere initial total 4-momentum [GeV]: "
                        << momentum_total;
  return start_time_;
}

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Member Data Documentation

radius_

double smash::SphereModus::radius_

private

Sphere radius (in fm/c)

Definition at line 78 of file spheremodus.h.

sphere_temperature_

double smash::SphereModus::sphere_temperature_

private

Temperature for momentum distribution (in GeV)

Definition at line 80 of file spheremodus.h.

start_time_

const double smash::SphereModus::start_time_ = 0.

private

Starting time for the Sphere.

Definition at line 82 of file spheremodus.h.

use_thermal_

const bool smash::SphereModus::use_thermal_ = false

private

Whether to use a thermal initialization for all particles instead of specific numbers.

Definition at line 87 of file spheremodus.h.

mub_

const double smash::SphereModus::mub_

private

Baryon chemical potential for thermal initialization; only used if use_thermal_ is true.

Definition at line 92 of file spheremodus.h.

mus_

const double smash::SphereModus::mus_

private

Strange chemical potential for thermal initialization; only used if use_thermal_ is true.

Definition at line 97 of file spheremodus.h.

account_for_resonance_widths_

const bool smash::SphereModus::account_for_resonance_widths_

private

In case of thermal initialization: true – account for resonance spectral functions, while computing multiplicities and sampling masses, false – simply use pole masses.

Definition at line 103 of file spheremodus.h.

init_multipl_

const std::map<PdgCode, int> smash::SphereModus::init_multipl_

private

Particle multiplicities at initialization; required if use_thermal_ is false.

Definition at line 108 of file spheremodus.h.

average_multipl_

std::map<PdgCode, double> smash::SphereModus::average_multipl_

private

Average multiplicities in case of thermal initialization.

Saved to avoid recalculating at every event

Definition at line 113 of file spheremodus.h.

init_distr_

const SphereInitialCondition smash::SphereModus::init_distr_

private

Initialization scheme for momenta in the sphere; used for expanding metric setup.

Definition at line 118 of file spheremodus.h.

insert_jet_

const bool smash::SphereModus::insert_jet_ = false

private

Whether to insert a single high energy particle at the center of the expanding sphere (0,0,0).

This particle will initially be moving along the x axis, outwards from the sphere.

Definition at line 124 of file spheremodus.h.

jet_pdg_

const PdgCode smash::SphereModus::jet_pdg_

private

Pdg of the particle to use as a jet; necessary if insert_jet_ is true, unused otherwise.

Definition at line 129 of file spheremodus.h.

jet_mom_

const double smash::SphereModus::jet_mom_

private

Initial momentum of the jet particle; only used if insert_jet_ is true.

Definition at line 133 of file spheremodus.h.

---

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

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