Herwig::DecayPhaseSpaceChannel Class Reference

This class is designed to store the information needed for a given phase-space channel for use by the multi-channel phase space decayer and perform the generation of the phase space for that channel. More...

#include <DecayPhaseSpaceChannel.h>

Inheritance diagram for Herwig::DecayPhaseSpaceChannel:

List of all members.

Public Member Functions
Standard constructors and destructors.
	DecayPhaseSpaceChannel ()
	Default constructor.
	DecayPhaseSpaceChannel (tcDecayPhaseSpaceModePtr)
	Constructor with a pointer to a DecayPhaseSpaceMode.
Set-up Members
void	addIntermediate (PDPtr part, int jac, double power, int dau1, int dau2)
	Add a new intermediate particle.
void	resetIntermediate (tcPDPtr part, Energy mass, Energy width)
	Reset the properties of an intermediate particle.
void	resetDaughter (int oldp, int newp)
Functions used by the persistent I/O system.
void	persistentOutput (PersistentOStream &os) const
	Function used to write out object persistently.
void	persistentInput (PersistentIStream &is, int version)
	Function used to read in object persistently.
Static Public Member Functions
static void	Init ()
	Standard Init function used to initialize the interfaces.
Protected Member Functions
Phase-Space Generation Members
vector< Lorentz5Momentum >	generateMomenta (const Lorentz5Momentum &pin, const vector< Energy > &massext)
	Generate the momenta of the external particles.
double	generateWeight (const vector< Lorentz5Momentum > &output)
	Generate the weight for this channel given a phase space configuration.
void	generateIntermediates (bool cc, const Particle &in, ParticleVector &out)
	Generate the final-state particles including the intermediate resonances.
void	twoBodyDecay (const Lorentz5Momentum &p, const Energy m1, const Energy m2, Lorentz5Momentum &p1, Lorentz5Momentum &p2)
	Calculate the momenta for a two body decay The return value indicates success or failure.
Clone Methods.
virtual IBPtr	clone () const
	Make a simple clone of this object.
virtual IBPtr	fullclone () const
	Make a clone of this object, possibly modifying the cloned object to make it sane.
Standard Interfaced functions.
virtual void	doinit ()
	Initialize this object after the setup phase before saving and EventGenerator to disk.
virtual void	doinitrun ()
	Initialize this object.
Private Member Functions
DecayPhaseSpaceChannel &	operator= (const DecayPhaseSpaceChannel &)
	Private and non-existent assignment operator.
double	atanhelper_ (int ires, Energy limit)
	Helper function for the weight calculation.
Mass Generation Members
Energy	generateMass (int ires, Energy lower, Energy upper)
	Generate the mass of a resonance.
InvEnergy2	massWeight (int ires, Energy moff, Energy lower, Energy upper)
	Return the weight for a given resonance.
Private Attributes
tcDecayPhaseSpaceModePtr	_mode
	pointer to the mode
vector< PDPtr >	_intpart
	Pointers to the particle data objects of the intermediate particles.
vector< int >	_jactype
	The type of jacobian to be used for the intermediates.
vector< Energy >	_intmass
	The mass of the intermediates.
vector< Energy >	_intwidth
	The width of the intermediates.
vector< Energy2 >	_intmass2
	The mass squared of the intermediate particles.
vector< Energy2 >	_intmwidth
	The mass times the width for the intermediate particles.
vector< double >	_intpower
	The power for the intermediate resonance.
vector< int >	_intdau1
	The first daughter of the intermediate resonance.
vector< int >	_intdau2
	The second daughter of the intermediate resonance.
vector< vector< int > >	_intext
	The external particles that an intermediate particle final decays to.
Static Private Attributes
static ClassDescription < DecayPhaseSpaceChannel >	initDecayPhaseSpaceChannel
	Describe a concrete class with persistent data.
Friends
class	DecayPhaseSpaceMode
	DecayPhaseSpaceMode is a friend to avoid making many of the phase space generation members public.
ostream &	operator<< (ostream &, const DecayPhaseSpaceChannel &)
	A friend output operator to allow the channel to be outputted for debugging purposes.

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Detailed Description

This class is designed to store the information needed for a given phase-space channel for use by the multi-channel phase space decayer and perform the generation of the phase space for that channel.

The decay channel is specified as a series of decays to either external particles or other intermediates. For each intermediate the Jacobian to be used can be either a Breit-Wigner(0) or a power-law (1).

The class is then capable of generating a phase-space point using this channel and computing the weight of a given point for use in a multi-channel phase space integration using the DecayPhaseSpaceMode class.

The class is designed so that the phase-space channels can either by specified using the addIntermediate method directly or via the repository. (In practice at the moment all the channels are constructed by the relevant decayers using the former method at the moment.)

See also:

DecayPhaseSpaceMode

DecayIntegrator

Author:

Peter Richardson

Definition at line 52 of file DecayPhaseSpaceChannel.h.

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Constructor & Destructor Documentation

Herwig::DecayPhaseSpaceChannel::DecayPhaseSpaceChannel

(

tcDecayPhaseSpaceModePtr

)

Constructor with a pointer to a DecayPhaseSpaceMode.

This is the constructor which should normally be used in decayers.

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Member Function Documentation

void Herwig::DecayPhaseSpaceChannel::addIntermediate	(	PDPtr	part,
		int	jac,
		double	power,
		int	dau1,
		int	dau2
	)		[inline]

Add a new intermediate particle.

Parameters:

part	A pointer to the particle data object for the intermediate.
jac	The jacobian to be used for the generation of the particle's mass 0 is a Breit-Wigner and 1 is a power-law
power	The power to beb used for the mass generation if a power law mass distribution is chosen.
dau1	The first daughter. If this is postive it is the th outgoing particle (0 is the incoming particle), if it is negative it is the intermediate. The intermediates are specified in the order they are added with 0 being the incoming particle.
dau2	The first daughter. If this is postive it is the th outgoing particle (0 is the incoming particle), if it is negative it is the intermediate. The intermediates are specified in the order they are added with 0 being the incoming particle.

Definition at line 102 of file DecayPhaseSpaceChannel.h.

double Herwig::DecayPhaseSpaceChannel::atanhelper_	(	int	ires,
		Energy	limit
	)		[private]

Helper function for the weight calculation.

Parameters:

ires	The resonance to be generated.
limit	The limit on the particle's mass.

virtual IBPtr Herwig::DecayPhaseSpaceChannel::clone

(

)

const [inline, protected, virtual]

Make a simple clone of this object.

Returns:

a pointer to the new object.

Implements ThePEG::InterfacedBase.

Definition at line 227 of file DecayPhaseSpaceChannel.h.

virtual void Herwig::DecayPhaseSpaceChannel::doinit

(

)

[protected, virtual]

Initialize this object after the setup phase before saving and EventGenerator to disk.

Exceptions:

InitException

if object could not be initialized properly.

Reimplemented from ThePEG::InterfacedBase.

virtual void Herwig::DecayPhaseSpaceChannel::doinitrun

(

)

[protected, virtual]

Initialize this object.

Called in the run phase just before a run begins.

Reimplemented from ThePEG::InterfacedBase.

virtual IBPtr Herwig::DecayPhaseSpaceChannel::fullclone

(

)

const [inline, protected, virtual]

Make a clone of this object, possibly modifying the cloned object to make it sane.

Returns:

a pointer to the new object.

Reimplemented from ThePEG::InterfacedBase.

Definition at line 233 of file DecayPhaseSpaceChannel.h.

void Herwig::DecayPhaseSpaceChannel::generateIntermediates	(	bool	cc,
		const Particle &	in,
		ParticleVector &	out
	)		[protected]

Generate the final-state particles including the intermediate resonances.

This method takes the outgoing particles and adds the intermediate particles specified by this phase-space channel. This is to allow a given set of intermediates to be specified even when there is interference between different intermediate states.

Parameters:

cc	Whether the particles are the mode specified or its charge conjugate.
in	The incoming particles.
out	The outgoing particles.

Energy Herwig::DecayPhaseSpaceChannel::generateMass	(	int	ires,
		Energy	lower,
		Energy	upper
	)		[private]

Generate the mass of a resonance.

Parameters:

ires	The resonance to be generated.
lower	The lower limit on the particle's mass.
upper	The upper limit on the particle's mass.

vector<Lorentz5Momentum> Herwig::DecayPhaseSpaceChannel::generateMomenta	(	const Lorentz5Momentum &	pin,
		const vector< Energy > &	massext
	)		[protected]

Generate the momenta of the external particles.

This member uses the masses of the external particles generated by the DecayPhaseMode class and the intermediates for the channel to generate the momenta of the decay products.

Parameters:

pin	The momenta of the decay products. This is outputed by the member.
massext	The masses of the particles. This is to allow inclusion of off-shell effects for the external particles.

double Herwig::DecayPhaseSpaceChannel::generateWeight

(

const vector< Lorentz5Momentum > &

output

)

[protected]

Generate the weight for this channel given a phase space configuration.

This member generates the weight for a given phase space configuration and is used by the DecayPhaseSpaceMode class to compute the denominator of the weight in the multi-channel integration.

Parameters:

output

The momenta of the outgoing particles.

InvEnergy2 Herwig::DecayPhaseSpaceChannel::massWeight	(	int	ires,
		Energy	moff,
		Energy	lower,
		Energy	upper
	)		[private]

Return the weight for a given resonance.

Parameters:

ires	The resonance to be generated.
moff	The mass of the resonance.
lower	The lower limit on the particle's mass.
upper	The upper limit on the particle's mass.

void Herwig::DecayPhaseSpaceChannel::persistentInput	(	PersistentIStream &	is,
		int	version
	)

Function used to read in object persistently.

Parameters:

is	the persistent input stream read from.
version	the version number of the object when written.

Reimplemented from ThePEG::Interfaced.

void Herwig::DecayPhaseSpaceChannel::persistentOutput

(

PersistentOStream &

os

)

const

Function used to write out object persistently.

Parameters:

os	the persistent output stream written to.

Reimplemented from ThePEG::Interfaced.

void Herwig::DecayPhaseSpaceChannel::resetIntermediate	(	tcPDPtr	part,
		Energy	mass,
		Energy	width
	)		[inline]

Reset the properties of an intermediate particle.

This member is used when a Decayer is used a different value for either the mass or width of a resonace to that in the ParticleData object. This improves the efficiency of the integration.

Parameters:

part	A pointer to the particle data object for the intermediate.
mass	The new mass of the intermediate
width	The new width of the intermediate.

Definition at line 119 of file DecayPhaseSpaceChannel.h.

void Herwig::DecayPhaseSpaceChannel::twoBodyDecay	(	const Lorentz5Momentum &	p,
		const Energy	m1,
		const Energy	m2,
		Lorentz5Momentum &	p1,
		Lorentz5Momentum &	p2
	)		[protected]

Calculate the momenta for a two body decay The return value indicates success or failure.

Parameters:

p	The momentum of the decaying particle
m1	The mass of the first decay product
m2	The mass of the second decay product
p1	The momentum of the first decay product
p2	The momentum of the second decay product

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

• DecayPhaseSpaceChannel.h