Utility class to generate n-body event, with constant cross-section (default) or with Fermi energy dependence (opt="Fermi").

The event is generated in the center-of-mass frame, but the decay products are finally boosted using the betas of the original particle.

The code is based on the GENBOD function (W515 from CERNLIB) using the Raubold and Lynch method F. James, Monte Carlo Phase Space, CERN 68-15 (1968)

see example of use in PhaseSpace.C

Note that Momentum, Energy units are Gev/C, GeV

Definition at line 15 of file TGenPhaseSpace.h.

Public Member Functions
	TGenPhaseSpace ()

	TGenPhaseSpace (const TGenPhaseSpace &gen)
	Copy constructor.

	~TGenPhaseSpace () override

Double_t	Generate ()
	Generate a random final state.

TLorentzVector *	GetDecay (Int_t n)
	Return Lorentz vector corresponding to decay n.

Int_t	GetNt () const

Double_t	GetWtMax () const

TClass *	IsA () const override

TGenPhaseSpace &	operator= (const TGenPhaseSpace &gen)
	Assignment operator.

Bool_t	SetDecay (TLorentzVector &P, Int_t nt, const Double_t mass, Option_t opt="")
	Input:

void	Streamer (TBuffer &) override
	Stream an object of class TObject.

void	StreamerNVirtual (TBuffer &ClassDef_StreamerNVirtual_b)

Public Member Functions inherited from TObject
	TObject ()
	TObject constructor.

	TObject (const TObject &object)
	TObject copy ctor.

virtual	~TObject ()
	TObject destructor.

void	AbstractMethod (const char *method) const
	Use this method to implement an "abstract" method that you don't want to leave purely abstract.

virtual void	AppendPad (Option_t *option="")
	Append graphics object to current pad.

virtual void	Browse (TBrowser *b)
	Browse object. May be overridden for another default action.

ULong_t	CheckedHash ()
	Check and record whether this class has a consistent Hash/RecursiveRemove setup (*) and then return the regular Hash value for this object.

virtual const char *	ClassName () const
	Returns name of class to which the object belongs.

virtual void	Clear (Option_t *="")

virtual TObject *	Clone (const char *newname="") const
	Make a clone of an object using the Streamer facility.

virtual Int_t	Compare (const TObject *obj) const
	Compare abstract method.

virtual void	Copy (TObject &object) const
	Copy this to obj.

virtual void	Delete (Option_t *option="")
	Delete this object.

virtual Int_t	DistancetoPrimitive (Int_t px, Int_t py)
	Computes distance from point (px,py) to the object.

virtual void	Draw (Option_t *option="")
	Default Draw method for all objects.

virtual void	DrawClass () const
	Draw class inheritance tree of the class to which this object belongs.

virtual TObject *	DrawClone (Option_t *option="") const
	Draw a clone of this object in the current selected pad with: `gROOT->SetSelectedPad(c1)`.

virtual void	Dump () const
	Dump contents of object on stdout.

virtual void	Error (const char method, const char msgfmt,...) const
	Issue error message.

virtual void	Execute (const char method, const char params, Int_t *error=nullptr)
	Execute method on this object with the given parameter string, e.g.

virtual void	Execute (TMethod method, TObjArray params, Int_t *error=nullptr)
	Execute method on this object with parameters stored in the TObjArray.

virtual void	ExecuteEvent (Int_t event, Int_t px, Int_t py)
	Execute action corresponding to an event at (px,py).

virtual void	Fatal (const char method, const char msgfmt,...) const
	Issue fatal error message.

virtual TObject *	FindObject (const char *name) const
	Must be redefined in derived classes.

virtual TObject *	FindObject (const TObject *obj) const
	Must be redefined in derived classes.

virtual Option_t *	GetDrawOption () const
	Get option used by the graphics system to draw this object.

virtual const char *	GetIconName () const
	Returns mime type name of object.

virtual const char *	GetName () const
	Returns name of object.

virtual char *	GetObjectInfo (Int_t px, Int_t py) const
	Returns string containing info about the object at position (px,py).

virtual Option_t *	GetOption () const

virtual const char *	GetTitle () const
	Returns title of object.

virtual UInt_t	GetUniqueID () const
	Return the unique object id.

virtual Bool_t	HandleTimer (TTimer *timer)
	Execute action in response of a timer timing out.

virtual ULong_t	Hash () const
	Return hash value for this object.

Bool_t	HasInconsistentHash () const
	Return true is the type of this object is known to have an inconsistent setup for Hash and RecursiveRemove (i.e.

virtual void	Info (const char method, const char msgfmt,...) const
	Issue info message.

virtual Bool_t	InheritsFrom (const char *classname) const
	Returns kTRUE if object inherits from class "classname".

virtual Bool_t	InheritsFrom (const TClass *cl) const
	Returns kTRUE if object inherits from TClass cl.

virtual void	Inspect () const
	Dump contents of this object in a graphics canvas.

void	InvertBit (UInt_t f)

Bool_t	IsDestructed () const
	IsDestructed.

virtual Bool_t	IsEqual (const TObject *obj) const
	Default equal comparison (objects are equal if they have the same address in memory).

virtual Bool_t	IsFolder () const
	Returns kTRUE in case object contains browsable objects (like containers or lists of other objects).

R__ALWAYS_INLINE Bool_t	IsOnHeap () const

virtual Bool_t	IsSortable () const

R__ALWAYS_INLINE Bool_t	IsZombie () const

virtual void	ls (Option_t *option="") const
	The ls function lists the contents of a class on stdout.

void	MayNotUse (const char *method) const
	Use this method to signal that a method (defined in a base class) may not be called in a derived class (in principle against good design since a child class should not provide less functionality than its parent, however, sometimes it is necessary).

virtual Bool_t	Notify ()
	This method must be overridden to handle object notification.

void	Obsolete (const char method, const char asOfVers, const char *removedFromVers) const
	Use this method to declare a method obsolete.

void	operator delete (void *ptr)
	Operator delete.

void	operator delete[] (void *ptr)
	Operator delete [].

void *	operator new (size_t sz)

void *	operator new (size_t sz, void *vp)

void *	operator new[] (size_t sz)

void *	operator new[] (size_t sz, void *vp)

TObject &	operator= (const TObject &rhs)
	TObject assignment operator.

virtual void	Paint (Option_t *option="")
	This method must be overridden if a class wants to paint itself.

virtual void	Pop ()
	Pop on object drawn in a pad to the top of the display list.

virtual void	Print (Option_t *option="") const
	This method must be overridden when a class wants to print itself.

virtual Int_t	Read (const char *name)
	Read contents of object with specified name from the current directory.

virtual void	RecursiveRemove (TObject *obj)
	Recursively remove this object from a list.

void	ResetBit (UInt_t f)

virtual void	SaveAs (const char filename="", Option_t option="") const
	Save this object in the file specified by filename.

virtual void	SavePrimitive (std::ostream &out, Option_t *option="")
	Save a primitive as a C++ statement(s) on output stream "out".

void	SetBit (UInt_t f)

void	SetBit (UInt_t f, Bool_t set)
	Set or unset the user status bits as specified in f.

virtual void	SetDrawOption (Option_t *option="")
	Set drawing option for object.

virtual void	SetUniqueID (UInt_t uid)
	Set the unique object id.

void	StreamerNVirtual (TBuffer &ClassDef_StreamerNVirtual_b)

virtual void	SysError (const char method, const char msgfmt,...) const
	Issue system error message.

R__ALWAYS_INLINE Bool_t	TestBit (UInt_t f) const

Int_t	TestBits (UInt_t f) const

virtual void	UseCurrentStyle ()
	Set current style settings in this object This function is called when either TCanvas::UseCurrentStyle or TROOT::ForceStyle have been invoked.

virtual void	Warning (const char method, const char msgfmt,...) const
	Issue warning message.

virtual Int_t	Write (const char *name=nullptr, Int_t option=0, Int_t bufsize=0)
	Write this object to the current directory.

virtual Int_t	Write (const char *name=nullptr, Int_t option=0, Int_t bufsize=0) const
	Write this object to the current directory.

Static Public Member Functions
static TClass *	Class ()

static const char *	Class_Name ()

static constexpr Version_t	Class_Version ()

static const char *	DeclFileName ()

Static Public Member Functions inherited from TObject
static TClass *	Class ()

static const char *	Class_Name ()

static constexpr Version_t	Class_Version ()

static const char *	DeclFileName ()

static Longptr_t	GetDtorOnly ()
	Return destructor only flag.

static Bool_t	GetObjectStat ()
	Get status of object stat flag.

static void	SetDtorOnly (void *obj)
	Set destructor only flag.

static void	SetObjectStat (Bool_t stat)
	Turn on/off tracking of objects in the TObjectTable.

Private Member Functions
Double_t	PDK (Double_t a, Double_t b, Double_t c)
	The PDK function.

Private Attributes
Double_t	fBeta [3]

TLorentzVector	fDecPro [18]

Double_t	fMass [18]

Int_t	fNt

Double_t	fTeCmTm

Double_t	fWtMax

Additional Inherited Members
Public Types inherited from TObject
enum	{ kIsOnHeap = 0x01000000 , kNotDeleted = 0x02000000 , kZombie = 0x04000000 , kInconsistent = 0x08000000 , kBitMask = 0x00ffffff }

enum	{ kSingleKey = (1ULL << ( 0 )) , kOverwrite = (1ULL << ( 1 )) , kWriteDelete = (1ULL << ( 2 )) }

enum	EDeprecatedStatusBits { kObjInCanvas = (1ULL << ( 3 )) }

enum	EStatusBits { kCanDelete = (1ULL << ( 0 )) , kMustCleanup = (1ULL << ( 3 )) , kIsReferenced = (1ULL << ( 4 )) , kHasUUID = (1ULL << ( 5 )) , kCannotPick = (1ULL << ( 6 )) , kNoContextMenu = (1ULL << ( 8 )) , kInvalidObject = (1ULL << ( 13 )) }

Protected Types inherited from TObject
enum	{ kOnlyPrepStep = (1ULL << ( 3 )) }

Protected Member Functions inherited from TObject
virtual void	DoError (int level, const char location, const char fmt, va_list va) const
	Interface to ErrorHandler (protected).

void	MakeZombie ()

#include <TGenPhaseSpace.h>

Inheritance diagram for TGenPhaseSpace:

[legend]

Constructor & Destructor Documentation

◆ TGenPhaseSpace() [1/2]

TGenPhaseSpace::TGenPhaseSpace ( )

inline

Definition at line 27 of file TGenPhaseSpace.h.

◆ TGenPhaseSpace() [2/2]

TGenPhaseSpace::TGenPhaseSpace ( const TGenPhaseSpace & gen )

Copy constructor.

Definition at line 57 of file TGenPhaseSpace.cxx.

◆ ~TGenPhaseSpace()

TGenPhaseSpace::~TGenPhaseSpace ( )

inlineoverride

Definition at line 29 of file TGenPhaseSpace.h.

Member Function Documentation

◆ Class()

static TClass * TGenPhaseSpace::Class ( )

static

Returns: TClass describing this class

◆ Class_Name()

static const char * TGenPhaseSpace::Class_Name ( )

static

Returns: Name of this class

◆ Class_Version()

static constexpr Version_t TGenPhaseSpace::Class_Version ( )

inlinestaticconstexpr

Returns: Version of this class

Definition at line 39 of file TGenPhaseSpace.h.

◆ DeclFileName()

static const char * TGenPhaseSpace::DeclFileName ( )

inlinestatic

Returns: Name of the file containing the class declaration

Definition at line 39 of file TGenPhaseSpace.h.

◆ Generate()

Double_t TGenPhaseSpace::Generate ( )

Generate a random final state.

The function returns the weight of the current event. The TLorentzVector of each decay product can be obtained using GetDecay(n).

Note that Momentum, Energy units are Gev/C, GeV

Definition at line 98 of file TGenPhaseSpace.cxx.

◆ GetDecay()

TLorentzVector * TGenPhaseSpace::GetDecay ( Int_t n )

Return Lorentz vector corresponding to decay n.

Definition at line 173 of file TGenPhaseSpace.cxx.

◆ GetNt()

Int_t TGenPhaseSpace::GetNt ( ) const

inline

Definition at line 36 of file TGenPhaseSpace.h.

◆ GetWtMax()

Double_t TGenPhaseSpace::GetWtMax ( ) const

inline

Definition at line 37 of file TGenPhaseSpace.h.

◆ IsA()

TClass * TGenPhaseSpace::IsA ( ) const

inlineoverridevirtual

Returns: TClass describing current object

Reimplemented from TObject.

Definition at line 39 of file TGenPhaseSpace.h.

◆ operator=()

TGenPhaseSpace & TGenPhaseSpace::operator= ( const TGenPhaseSpace & gen )

Assignment operator.

Definition at line 75 of file TGenPhaseSpace.cxx.

◆ PDK()

Double_t TGenPhaseSpace::PDK	(	Double_t	a,
		Double_t	b,
		Double_t	c
	)

private

The PDK function.

Definition at line 34 of file TGenPhaseSpace.cxx.

◆ SetDecay()

Bool_t TGenPhaseSpace::SetDecay	(	TLorentzVector &	P,
		Int_t	nt,
		const Double_t *	mass,
		Option_t *	opt = `""`
	)

Input:

TLorentzVector &P: decay particle (Momentum, Energy units are Gev/C, GeV)
Int_t nt: number of decay products
Double_t *mass: array of decay product masses
Option_t *opt: default -> constant cross section "Fermi" -> Fermi energy dependence Return value:
kTRUE: the decay is permitted by kinematics
kFALSE: the decay is forbidden by kinematics

Definition at line 192 of file TGenPhaseSpace.cxx.

◆ Streamer()

void TGenPhaseSpace::Streamer ( TBuffer & R__b )

overridevirtual

Stream an object of class TObject.

Reimplemented from TObject.

◆ StreamerNVirtual()

void TGenPhaseSpace::StreamerNVirtual ( TBuffer & ClassDef_StreamerNVirtual_b )

inline

Definition at line 39 of file TGenPhaseSpace.h.

Member Data Documentation

◆ fBeta

Double_t TGenPhaseSpace::fBeta[3]

private

Definition at line 19 of file TGenPhaseSpace.h.

◆ fDecPro

TLorentzVector TGenPhaseSpace::fDecPro[18]

private

Definition at line 22 of file TGenPhaseSpace.h.

◆ fMass

Double_t TGenPhaseSpace::fMass[18]

private

Definition at line 18 of file TGenPhaseSpace.h.

◆ fNt

Int_t TGenPhaseSpace::fNt

private

Definition at line 17 of file TGenPhaseSpace.h.

◆ fTeCmTm

Double_t TGenPhaseSpace::fTeCmTm

private

Definition at line 20 of file TGenPhaseSpace.h.

◆ fWtMax

Double_t TGenPhaseSpace::fWtMax

private

Definition at line 21 of file TGenPhaseSpace.h.

Libraries for TGenPhaseSpace:

[legend]

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

math/physics/inc/TGenPhaseSpace.h
math/physics/src/TGenPhaseSpace.cxx

Public Member Functions

Static Public Member Functions

Private Member Functions

Private Attributes

Additional Inherited Members

Constructor & Destructor Documentation

◆ TGenPhaseSpace() [1/2]

◆ TGenPhaseSpace() [2/2]

◆ ~TGenPhaseSpace()

Member Function Documentation

◆ Class()

◆ Class_Name()

◆ Class_Version()

◆ DeclFileName()

◆ Generate()

◆ GetDecay()

◆ GetNt()

◆ GetWtMax()

◆ IsA()

◆ operator=()

◆ PDK()

◆ SetDecay()

◆ Streamer()

◆ StreamerNVirtual()

Member Data Documentation

◆ fBeta

◆ fDecPro

◆ fMass

◆ fNt

◆ fTeCmTm

◆ fWtMax