smash::ParticleData Class Reference

#include <particledata.h>

ParticleData contains the dynamic information of a certain particle.

Each particle has its momentum, position and other relevant physical data entry.

Definition at line 52 of file particledata.h.

Collaboration diagram for smash::ParticleData:

Public Member Functions
	ParticleData (const ParticleType &particle_type, int unique_id=-1)
	Create a new particle with the given particle_type and optionally a specific unique_id. More...
int	id () const
	Get the id of the particle. More...
void	set_id (int i)
	Set id of the particle. More...
PdgCode	pdgcode () const
	Get the pdgcode of the particle. More...
bool	is_hadron () const
bool	is_baryon () const
bool	is_rho () const
double	pole_mass () const
	Get the particle's pole mass ("on-shell"). More...
double	effective_mass () const
	Get the particle's effective mass. More...
const ParticleType &	type () const
	Get the type of the particle. More...
uint32_t	id_process () const
	Get the id of the last action. More...
HistoryData	get_history () const
	Get history information. More...
void	set_history (int ncoll, uint32_t pid, ProcessType pt, double time_of_or, const ParticleList &plist)
	Store history information. More...
const FourVector &	momentum () const
	Get the particle's 4-momentum. More...
void	set_4momentum (const FourVector &momentum_vector)
	Set the particle's 4-momentum directly. More...
void	set_4momentum (double mass, const ThreeVector &mom)
	Set the momentum of the particle given its mass and momentum three-vector. More...
void	set_4momentum (double mass, double px, double py, double pz)
	Set the momentum of the particle. More...
void	set_3momentum (const ThreeVector &mom)
	Set the momentum of the particle without modifying the energy. More...
const FourVector &	position () const
	Get the particle's position in Minkowski space. More...
void	set_4position (const FourVector &pos)
	Set the particle's 4-position directly. More...
void	set_3position (const ThreeVector &pos)
	Set particle's 3-position. More...
ParticleData	translated (const ThreeVector &delta) const
	Translate the particle position. More...
double	formation_time () const
	Get the absolute formation time of the particle. More...
double	begin_formation_time () const
	Get the absolute time, where the cross section scaling factor slowly starts increasing from the given scaling factor to 1. More...
void	set_formation_time (const double &form_time)
	Set the absolute formation time. More...
void	set_slow_formation_times (double begin_form_time, double form_time)
	Set the time, when the cross section scaling factor begins, and finishes to increase from the given cross section scaling factor to 1. More...
const double &	initial_xsec_scaling_factor () const
	Get the initially assigned cross section scaling factor. More...
void	set_cross_section_scaling_factor (const double &xsec_scal)
	Set the particle's initial cross_section_scaling_factor. More...
ThreeVector	velocity () const
	Get the velocity 3-vector. More...
double	inverse_gamma () const
	Get the inverse of the gamma factor from the current velocity of the particle. More...
void	boost (const ThreeVector &v)
	Apply a full Lorentz boost of momentum and position. More...
void	boost_momentum (const ThreeVector &v)
	Apply a Lorentz-boost to only the momentum. More...
bool	operator== (const ParticleData &a) const
	Check whether two particles have the same id. More...
bool	operator< (const ParticleData &a) const
	Check if this particle has a smaller id than another particle. More...
bool	operator== (int id_a) const
	Check if the particle has a given id. More...
bool	operator< (int id_a) const
	Check whether the particle's id is smaller than the given id. More...
	ParticleData (const ParticleType &ptype, int uid, int index)
	Construct a particle with the given type, id and index in Particles. More...
double	xsec_scaling_factor (double delta_time=0.) const
	Return the cross section scaling factor at a given time. More...

Static Public Attributes
static double	formation_power_ = 0.0
	Power with which the cross section scaling factor grows in time. More...

Private Member Functions
	ParticleData ()=default
	Default constructor. More...
void	copy_to (ParticleData &dst) const
	Copies some information of the particle to the given particle dst. More...

Private Attributes
int	id_ = -1
	Each particle has a unique identifier. More...
unsigned	index_ = std::numeric_limits<unsigned>::max()
	Internal index in the Particles list. More...
ParticleTypePtr	type_
	A reference to the ParticleType object for this particle (this contains all the static information). More...
bool	hole_ = false
	If true, the object is an entry in Particles::data_ and does not hold valid particle data. More...
FourVector	momentum_
	momenta of the particle: x0, x1, x2, x3 as E, px, py, pz More...
FourVector	position_
	position in space: x0, x1, x2, x3 as t, x, y, z More...
double	formation_time_ = 0.0
	Formation time at which the particle is fully formed given as an absolute value in the computational frame. More...
double	begin_formation_time_ = 0.0
	time when the cross section scaling factor starts to increase to 1 More...
double	initial_xsec_scaling_factor_ = 1.0
	Initial cross section scaling factor. More...
HistoryData	history_
	history information More...

Friends
class	Particles

Constructor & Destructor Documentation

ParticleData() [1/3]

smash::ParticleData::ParticleData ( const ParticleType &  particle_type, int  unique_id = -1  )

inlineexplicit

Create a new particle with the given particle_type and optionally a specific unique_id.

All other values are initialized to unphysical values.

Parameters

[in]	particle_type	Type of particle to be created
[in]	unique_id	id of particle to be created

Definition at line 63 of file particledata.h.

      : id_(unique_id), type_(&particle_type) {}

ParticleData() [2/3]

smash::ParticleData::ParticleData ( const ParticleType &  ptype, int  uid, int  index  )

inline

Construct a particle with the given type, id and index in Particles.

This constructor may only be called (directly or indirectly) from Particles. This constructor should be private, but can't be in order to support vector::emplace_back.

Parameters

[in]	ptype	Type of the particle to be constructed
[in]	uid	id of the particle to be constructed
[in]	index	index of the particle to be constructed

Definition at line 352 of file particledata.h.

      : id_(uid), index_(index), type_(&ptype) {}

ParticleData() [3/3]

smash::ParticleData::ParticleData ( )

privatedefault

Default constructor.

Member Function Documentation

id()

int smash::ParticleData::id ( ) const

inline

Get the id of the particle.

Returns

particle id

Definition at line 70 of file particledata.h.

{ return id_; }

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set_id()

void smash::ParticleData::set_id ( int  i )

inline

Set id of the particle.

Parameters

[in]

i

id to be assigned to the particle

Definition at line 75 of file particledata.h.

{ id_ = i; }

pdgcode()

PdgCode smash::ParticleData::pdgcode ( ) const

inline

Get the pdgcode of the particle.

Returns

pdgcode of the particle

Definition at line 81 of file particledata.h.

{ return type_->pdgcode(); }

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is_hadron()

bool smash::ParticleData::is_hadron ( ) const

inline

Returns

true if this is a baryon, antibaryon or meson.

Definition at line 85 of file particledata.h.

{ return type_->is_hadron(); }

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is_baryon()

bool smash::ParticleData::is_baryon ( ) const

inline

Returns

whether this PDG code identifies a baryon.

Definition at line 88 of file particledata.h.

{ return pdgcode().is_baryon(); }

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is_rho()

bool smash::ParticleData::is_rho ( ) const

inline

Returns

whether this is a rho meson (rho+/rho0/rho-)

Definition at line 91 of file particledata.h.

{ return type_->is_rho(); }

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pole_mass()

double smash::ParticleData::pole_mass ( ) const

inline

Get the particle's pole mass ("on-shell").

Returns

pole mass of the particle [GeV]

Definition at line 96 of file particledata.h.

{ return type_->mass(); }

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effective_mass()

double smash::ParticleData::effective_mass

(

)

const

Get the particle's effective mass.

Determined from the 4-momentum \(m=\sqrt{p_\mu p^\mu}\). Possibly "off-shell".

Returns

Effective mass [GeV]

Definition at line 21 of file particledata.cc.

                                          {
  const double m_pole = pole_mass();
  if (m_pole < really_small) {
    // prevent numerical problems with massless or very light particles
    return m_pole;
  } else {
    return momentum().abs();
  }
}

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type()

const ParticleType& smash::ParticleData::type ( ) const

inline

Get the type of the particle.

Returns

ParticleType object associated to this particle.

Definition at line 109 of file particledata.h.

{ return *type_; }

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id_process()

uint32_t smash::ParticleData::id_process ( ) const

inline

Get the id of the last action.

Returns

id of particle's latest collision

Definition at line 115 of file particledata.h.

{ return history_.id_process; }

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get_history()

HistoryData smash::ParticleData::get_history ( ) const

inline

Get history information.

Returns

particle history struct

Definition at line 120 of file particledata.h.

{ return history_; }

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set_history()

void smash::ParticleData::set_history	(	int	ncoll,
		uint32_t	pid,
		ProcessType	pt,
		double	time_of_or,
		const ParticleList &	plist
	)

Store history information.

The history contains the type of process and possibly the PdgCodes of the parent particles (plist). Note that history is not set for dileptons and photons.

Parameters

[in]	ncoll	particle's number of collisions
[in]	pid	id of the particle's latest process
[in]	pt	process type of the particle's latest process
[in]	time_of_or	time of latest collision [fm]
[in]	plist	list of parent particles

Definition at line 31 of file particledata.cc.

                                                          {
  if (pt != ProcessType::Wall) {
    history_.collisions_per_particle = ncoll;
    history_.time_last_collision = time_last_coll;
  }
  history_.id_process = pid;
  history_.process_type = pt;
  switch (pt) {
    case ProcessType::Decay:
    case ProcessType::Wall:
      // only store one parent
      history_.p1 = plist[0].pdgcode();
      history_.p2 = 0x0;
      break;
    case ProcessType::Elastic:
    case ProcessType::TwoToOne:
    case ProcessType::TwoToTwo:
    case ProcessType::StringSoftSingleDiffractiveAX:
    case ProcessType::StringSoftSingleDiffractiveXB:
    case ProcessType::StringSoftDoubleDiffractive:
    case ProcessType::StringSoftAnnihilation:
    case ProcessType::StringSoftNonDiffractive:
    case ProcessType::StringHard:
      // store two parent particles
      history_.p1 = plist[0].pdgcode();
      history_.p2 = plist[1].pdgcode();
      break;
    case ProcessType::Thermalization:
    case ProcessType::None:
      // nullify parents
      history_.p1 = 0x0;
      history_.p2 = 0x0;
      break;
  }
}

momentum()

const FourVector& smash::ParticleData::momentum ( ) const

inline

Get the particle's 4-momentum.

Returns

particle's 4-momentum [GeV]

Definition at line 139 of file particledata.h.

{ return momentum_; }

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set_4momentum() [1/3]

void smash::ParticleData::set_4momentum ( const FourVector &  momentum_vector )

inline

Set the particle's 4-momentum directly.

Parameters

[in]

momentum_vector

4-vector \(p^\mu = (E,\vec{p})^T\)

Definition at line 145 of file particledata.h.

                                                        {
    momentum_ = momentum_vector;
  }

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set_4momentum() [2/3]

void smash::ParticleData::set_4momentum ( double  mass, const ThreeVector &  mom  )

inline

Set the momentum of the particle given its mass and momentum three-vector.

Parameters

[in]	mass	the mass of the particle (without E_kin contribution) [GeV]
[in]	mom	the three-momentum of the particle [GeV]

Definition at line 155 of file particledata.h.

                                                          {
    momentum_ = FourVector(std::sqrt(mass * mass + mom * mom), mom);
  }

set_4momentum() [3/3]

void smash::ParticleData::set_4momentum ( double  mass, double  px, double  py, double  pz  )

inline

Set the momentum of the particle.

Parameters

[in]	mass	the mass of the particle (without E_kin contribution) [GeV]
[in]	px	x-component of the momentum [GeV]
[in]	py	y-component of the momentum [GeV]
[in]	pz	z-component of the momentum [GeV]

Definition at line 167 of file particledata.h.

                                                                   {
    momentum_ = FourVector(std::sqrt(mass * mass + px * px + py * py + pz * pz),
                           px, py, pz);
  }

set_3momentum()

void smash::ParticleData::set_3momentum ( const ThreeVector &  mom )

inline

Set the momentum of the particle without modifying the energy.

WARNING: Mass gets modified.

Parameters

[in]

mom

momentum 3-vector [GeV]

Definition at line 177 of file particledata.h.

                                             {
    momentum_ = FourVector(momentum_.x0(), mom);
  }

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position()

const FourVector& smash::ParticleData::position ( ) const

inline

Get the particle's position in Minkowski space.

Returns

particle's position 4-vector

Definition at line 185 of file particledata.h.

{ return position_; }

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set_4position()

void smash::ParticleData::set_4position ( const FourVector &  pos )

inline

Set the particle's 4-position directly.

Parameters

[in]

pos

position 4-vector

Definition at line 190 of file particledata.h.

{ position_ = pos; }

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set_3position()

void smash::ParticleData::set_3position ( const ThreeVector &  pos )

inline

Set particle's 3-position.

The time component is not changed

Parameters

[in]

pos

position 3-vector

Definition at line 197 of file particledata.h.

                                             {
    position_ = FourVector(position_.x0(), pos);
  }

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translated()

ParticleData smash::ParticleData::translated ( const ThreeVector &  delta ) const

inline

Translate the particle position.

Parameters

[in]

delta

3-vector by which the particle is translated [fm]

Definition at line 205 of file particledata.h.

                                                          {
    ParticleData p = *this;
    p.position_[1] += delta[0];
    p.position_[2] += delta[1];
    p.position_[3] += delta[2];
    return p;
  }

formation_time()

double smash::ParticleData::formation_time ( ) const

inline

Get the absolute formation time of the particle.

Returns

particle's formation time

Definition at line 217 of file particledata.h.

{ return formation_time_; }

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begin_formation_time()

double smash::ParticleData::begin_formation_time ( ) const

inline

Get the absolute time, where the cross section scaling factor slowly starts increasing from the given scaling factor to 1.

Returns

time, when scaling factor starts increasing

Definition at line 223 of file particledata.h.

{ return begin_formation_time_; }

set_formation_time()

void smash::ParticleData::set_formation_time ( const double &  form_time )

inline

Set the absolute formation time.

The particle's cross section scaling factor will be a Heavyside fuction of time.

Parameters

[in]

form_time

absolute formation time

Definition at line 232 of file particledata.h.

                                                   {
    formation_time_ = form_time;
    // cross section scaling factor will be a step function in time
    begin_formation_time_ = form_time;
  }

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set_slow_formation_times()

void smash::ParticleData::set_slow_formation_times ( double  begin_form_time, double  form_time  )

inline

Set the time, when the cross section scaling factor begins, and finishes to increase from the given cross section scaling factor to 1.

The cross section will only grow slowly, if the option is used.

Parameters

[in]	begin_form_time	time when the cross section starts to increase
[in]	form_time	time when the cross section reaches 1

Definition at line 246 of file particledata.h.

                                                                          {
    begin_formation_time_ = begin_form_time;
    formation_time_ = form_time;
  }

initial_xsec_scaling_factor()

const double& smash::ParticleData::initial_xsec_scaling_factor ( ) const

inline

Get the initially assigned cross section scaling factor.

Depending on the config, the cross section scaling factor might change with time, while this value will not be updated.

Returns

particle's initially assigned cross section scaling factor

Definition at line 259 of file particledata.h.

                                                    {
    return initial_xsec_scaling_factor_;
  }

set_cross_section_scaling_factor()

void smash::ParticleData::set_cross_section_scaling_factor ( const double &  xsec_scal )

inline

Set the particle's initial cross_section_scaling_factor.

All cross sections of this particle are scaled down by this factor until the formation time is over.

If the particle formation power is set to be positive, this will only be the initial scaling factor, while the actual scaling factor grows with time.

Parameters

[in]

xsec_scal

cross section scaling factor

Definition at line 274 of file particledata.h.

                                                                 {
    initial_xsec_scaling_factor_ = xsec_scal;
  }

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velocity()

ThreeVector smash::ParticleData::velocity ( ) const

inline

Get the velocity 3-vector.

Returns

3-velocity of the particle

Definition at line 282 of file particledata.h.

{ return momentum_.velocity(); }

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inverse_gamma()

double smash::ParticleData::inverse_gamma ( ) const

inline

Get the inverse of the gamma factor from the current velocity of the particle.

\[\frac{1}{\gamma}=\sqrt{1-v^2}\]

This functions is more efficient than calculating the gamma factor from velocity, since the velocity function must execute three divisions (for every space component of the momentum vector).

Returns

inverse gamma factor

Definition at line 296 of file particledata.h.

                               {
    return std::sqrt(1. - momentum_.sqr3() / (momentum_.x0() * momentum_.x0()));
  }

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boost()

void smash::ParticleData::boost ( const ThreeVector &  v )

inline

Apply a full Lorentz boost of momentum and position.

Parameters

[in]

v

boost 3-velocity

Definition at line 304 of file particledata.h.

                                   {
    set_4momentum(momentum_.LorentzBoost(v));
    set_4position(position_.LorentzBoost(v));
  }

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boost_momentum()

void smash::ParticleData::boost_momentum ( const ThreeVector &  v )

inline

Apply a Lorentz-boost to only the momentum.

Parameters

[in]

v

boost 3-veloctity

Definition at line 313 of file particledata.h.

                                            {
    set_4momentum(momentum_.LorentzBoost(v));
  }

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operator==() [1/2]

bool smash::ParticleData::operator== ( const ParticleData &  a ) const

inline

Check whether two particles have the same id.

Parameters

[in]

a

particle to compare to

Returns

whether the particles have the same id

Definition at line 322 of file particledata.h.

{ return this->id_ == a.id_; }

operator<() [1/2]

bool smash::ParticleData::operator< ( const ParticleData &  a ) const

inline

Check if this particle has a smaller id than another particle.

Parameters

[in]

a

particle to compare to

Returns

whether this particle has a smaller id than other particle

Definition at line 328 of file particledata.h.

{ return this->id_ < a.id_; }

operator==() [2/2]

bool smash::ParticleData::operator== ( int  id_a ) const

inline

Check if the particle has a given id.

Parameters

[in]

id_a

id to compare to

Returns

whether the particle has the given id

Definition at line 335 of file particledata.h.

{ return this->id_ == id_a; }

operator<() [2/2]

bool smash::ParticleData::operator< ( int  id_a ) const

inline

Check whether the particle's id is smaller than the given id.

Parameters

[in]

id_a

number to compare particle's id to

Definition at line 340 of file particledata.h.

{ return this->id_ < id_a; }

xsec_scaling_factor()

double smash::ParticleData::xsec_scaling_factor

(

double

delta_time = 0.

)

const

Return the cross section scaling factor at a given time.

Parameters

[in]

delta_time

scaling factor at current time plus this time will be returned.

Returns

the cross section scaling factor at a specified time.

Definition at line 69 of file particledata.cc.

                                                                {
  double time_of_interest = position_.x0() + delta_time;
  // cross section scaling factor at the time_of_interest
  double scaling_factor;

  if (formation_power_ <= 0.) {
    // use a step function to form particles
    if (time_of_interest < formation_time_) {
      // particles will not be fully formed at time of interest
      scaling_factor = initial_xsec_scaling_factor_;
    } else {
      // particles are fully formed at time of interest
      scaling_factor = 1.;
    }
  } else {
    // use smooth function to scale cross section (unless particles are already
    // fully formed at desired time or will start to form later)
    if (formation_time_ <= time_of_interest) {
      // particles are fully formed when colliding
      scaling_factor = 1.;
    } else if (begin_formation_time_ >= time_of_interest) {
      // particles will start formimg later
      scaling_factor = initial_xsec_scaling_factor_;
    } else {
      // particles are in the process of formation at the given time
      scaling_factor =
          initial_xsec_scaling_factor_ +
          (1. - initial_xsec_scaling_factor_) *
              std::pow((time_of_interest - begin_formation_time_) /
                           (formation_time_ - begin_formation_time_),
                       formation_power_);
    }
  }
  return scaling_factor;
}

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copy_to()

void smash::ParticleData::copy_to ( ParticleData &  dst ) const

inlineprivate

Copies some information of the particle to the given particle dst.

Specifically it avoids to copy id_, index_, and type_.

Parameters

[in]

dst

particle values are copied to

Definition at line 378 of file particledata.h.

                                        {
    dst.history_ = history_;
    dst.momentum_ = momentum_;
    dst.position_ = position_;
    dst.formation_time_ = formation_time_;
    dst.initial_xsec_scaling_factor_ = initial_xsec_scaling_factor_;
    dst.begin_formation_time_ = begin_formation_time_;
  }

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Friends And Related Function Documentation

Particles

friend class Particles

friend

Definition at line 368 of file particledata.h.

Member Data Documentation

formation_power_

double smash::ParticleData::formation_power_ = 0.0

static

Power with which the cross section scaling factor grows in time.

Definition at line 365 of file particledata.h.

id_

int smash::ParticleData::id_ = -1

private

Each particle has a unique identifier.

This identifier is used for identifying the particle in the output files. It is specifically not used for searching for ParticleData objects in lists of particles, though it may be used to identify two ParticleData objects as referencing the same particle. This is why the comparison operators depend only on the id_ member.

Definition at line 395 of file particledata.h.

index_

unsigned smash::ParticleData::index_ = std::numeric_limits<unsigned>::max()

private

Internal index in the Particles list.

This number is used to find the Experiment-wide original of this copy.

The value is read and written from the Particles class.

See also

Particles::data_

Definition at line 405 of file particledata.h.

type_

ParticleTypePtr smash::ParticleData::type_

private

A reference to the ParticleType object for this particle (this contains all the static information).

Default-initialized with an invalid index.

Definition at line 411 of file particledata.h.

hole_

bool smash::ParticleData::hole_ = false

private

If true, the object is an entry in Particles::data_ and does not hold valid particle data.

Specifically iterations over Particles must skip objects with hole_ == true. All other ParticleData instances should set this member to false.

See also

Particles::data_

Definition at line 425 of file particledata.h.

momentum_

FourVector smash::ParticleData::momentum_

private

momenta of the particle: x0, x1, x2, x3 as E, px, py, pz

Definition at line 428 of file particledata.h.

position_

FourVector smash::ParticleData::position_

private

position in space: x0, x1, x2, x3 as t, x, y, z

Definition at line 430 of file particledata.h.

formation_time_

double smash::ParticleData::formation_time_ = 0.0

private

Formation time at which the particle is fully formed given as an absolute value in the computational frame.

Definition at line 434 of file particledata.h.

begin_formation_time_

double smash::ParticleData::begin_formation_time_ = 0.0

private

time when the cross section scaling factor starts to increase to 1

Definition at line 436 of file particledata.h.

initial_xsec_scaling_factor_

double smash::ParticleData::initial_xsec_scaling_factor_ = 1.0

private

Initial cross section scaling factor.

1 by default, since a particle is fully formed in this case.

Definition at line 441 of file particledata.h.

history_

HistoryData smash::ParticleData::history_

private

history information

Definition at line 443 of file particledata.h.

---

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

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