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TGenPhaseSpace Class Reference

Legacy Code

TGenPhaseSpace is a legacy interface: there will be no bug fixes nor new developments. Therefore it is not recommended to use it in new long-term production code. But, depending on the context, using TGenPhaseSpace might still be a valid solution. No alternative classes are currently available.

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.
TLorentzVectorGetDecay (Int_t n)
 Return Lorentz vector corresponding to decay n.
Int_t GetNt () const
Double_t GetWtMax () const
TClassIsA () const override
TGenPhaseSpaceoperator= (const TGenPhaseSpace &gen)
 Assignment operator.
Bool_t SetDecay (TLorentzVector &P, Int_t nt, const Double_t *mass, Option_t *opt="")
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 TObjectClone (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 TObjectDrawClone (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 TObjectFindObject (const char *name) const
 Must be redefined in derived classes.
virtual TObjectFindObject (const TObject *obj) const
 Must be redefined in derived classes.
virtual Option_tGetDrawOption () 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_tGetOption () 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
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 (the base implementation is no-op).
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)
TObjectoperator= (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 TClassClass ()
static const char * Class_Name ()
static constexpr Version_t Class_Version ()
static const char * DeclFileName ()
- Static Public Member Functions inherited from TObject
static TClassClass ()
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:

Constructor & Destructor Documentation

◆ TGenPhaseSpace() [1/2]

TGenPhaseSpace::TGenPhaseSpace ( )

Definition at line 27 of file TGenPhaseSpace.h.

◆ TGenPhaseSpace() [2/2]

TGenPhaseSpace::TGenPhaseSpace ( const TGenPhaseSpace gen)

Copy constructor.

Definition at line 58 of file TGenPhaseSpace.cxx.

◆ ~TGenPhaseSpace()

TGenPhaseSpace::~TGenPhaseSpace ( )

Definition at line 29 of file TGenPhaseSpace.h.

Member Function Documentation

◆ Class()

static TClass * TGenPhaseSpace::Class ( )
TClass describing this class

◆ Class_Name()

static const char * TGenPhaseSpace::Class_Name ( )
Name of this class

◆ Class_Version()

static constexpr Version_t TGenPhaseSpace::Class_Version ( )
Version of this class

Definition at line 39 of file TGenPhaseSpace.h.

◆ DeclFileName()

static const char * TGenPhaseSpace::DeclFileName ( )
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 un-normalized 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 99 of file TGenPhaseSpace.cxx.

◆ GetDecay()

TLorentzVector * TGenPhaseSpace::GetDecay ( Int_t  n)

Return Lorentz vector corresponding to decay n.

Definition at line 174 of file TGenPhaseSpace.cxx.

◆ GetNt()

Int_t TGenPhaseSpace::GetNt ( ) const

Definition at line 36 of file TGenPhaseSpace.h.

◆ GetWtMax()

Double_t TGenPhaseSpace::GetWtMax ( ) const

Definition at line 37 of file TGenPhaseSpace.h.

◆ IsA()

TClass * TGenPhaseSpace::IsA ( ) const
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 76 of file TGenPhaseSpace.cxx.

◆ PDK()

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

The PDK function.

Definition at line 35 of file TGenPhaseSpace.cxx.

◆ SetDecay()

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


  • 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 193 of file TGenPhaseSpace.cxx.

◆ Streamer()

void TGenPhaseSpace::Streamer ( TBuffer R__b)

Stream an object of class TObject.

Reimplemented from TObject.

◆ StreamerNVirtual()

void TGenPhaseSpace::StreamerNVirtual ( TBuffer ClassDef_StreamerNVirtual_b)

Definition at line 39 of file TGenPhaseSpace.h.

Member Data Documentation

◆ fBeta

Double_t TGenPhaseSpace::fBeta[3]

Definition at line 19 of file TGenPhaseSpace.h.

◆ fDecPro

TLorentzVector TGenPhaseSpace::fDecPro[18]

Definition at line 22 of file TGenPhaseSpace.h.

◆ fMass

Double_t TGenPhaseSpace::fMass[18]

Definition at line 18 of file TGenPhaseSpace.h.

◆ fNt

Int_t TGenPhaseSpace::fNt

Definition at line 17 of file TGenPhaseSpace.h.

◆ fTeCmTm

Double_t TGenPhaseSpace::fTeCmTm

Definition at line 20 of file TGenPhaseSpace.h.

◆ fWtMax

Double_t TGenPhaseSpace::fWtMax

Definition at line 21 of file TGenPhaseSpace.h.

Libraries for TGenPhaseSpace:

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