class TGenPhaseSpace: public TObject


  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 $ROOTSYS/tutorials/physics/PhaseSpace.C

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

Function Members (Methods)

public:

	TGenPhaseSpace()
	TGenPhaseSpace(const TGenPhaseSpace& gen)
virtual	~TGenPhaseSpace()
void	TObject::AbstractMethod(const char* method) const
virtual void	TObject::AppendPad(Option_t* option = "")
virtual void	TObject::Browse(TBrowser* b)
static TClass*	Class()
virtual const char*	TObject::ClassName() const
virtual void	TObject::Clear(Option_t* = "")
virtual TObject*	TObject::Clone(const char* newname = "") const
virtual Int_t	TObject::Compare(const TObject* obj) const
virtual void	TObject::Copy(TObject& object) const
virtual void	TObject::Delete(Option_t* option = "")MENU
virtual Int_t	TObject::DistancetoPrimitive(Int_t px, Int_t py)
virtual void	TObject::Draw(Option_t* option = "")
virtual void	TObject::DrawClass() constMENU
virtual TObject*	TObject::DrawClone(Option_t* option = "") constMENU
virtual void	TObject::Dump() constMENU
virtual void	TObject::Error(const char* method, const char* msgfmt) const
virtual void	TObject::Execute(const char* method, const char* params, Int_t* error = 0)
virtual void	TObject::Execute(TMethod* method, TObjArray* params, Int_t* error = 0)
virtual void	TObject::ExecuteEvent(Int_t event, Int_t px, Int_t py)
virtual void	TObject::Fatal(const char* method, const char* msgfmt) const
virtual TObject*	TObject::FindObject(const char* name) const
virtual TObject*	TObject::FindObject(const TObject* obj) const
Double_t	Generate()
TLorentzVector*	GetDecay(Int_t n)
virtual Option_t*	TObject::GetDrawOption() const
static Long_t	TObject::GetDtorOnly()
virtual const char*	TObject::GetIconName() const
virtual const char*	TObject::GetName() const
Int_t	GetNt() const
virtual char*	TObject::GetObjectInfo(Int_t px, Int_t py) const
static Bool_t	TObject::GetObjectStat()
virtual Option_t*	TObject::GetOption() const
virtual const char*	TObject::GetTitle() const
virtual UInt_t	TObject::GetUniqueID() const
Double_t	GetWtMax() const
virtual Bool_t	TObject::HandleTimer(TTimer* timer)
virtual ULong_t	TObject::Hash() const
virtual void	TObject::Info(const char* method, const char* msgfmt) const
virtual Bool_t	TObject::InheritsFrom(const char* classname) const
virtual Bool_t	TObject::InheritsFrom(const TClass* cl) const
virtual void	TObject::Inspect() constMENU
void	TObject::InvertBit(UInt_t f)
virtual TClass*	IsA() const
virtual Bool_t	TObject::IsEqual(const TObject* obj) const
virtual Bool_t	TObject::IsFolder() const
Bool_t	TObject::IsOnHeap() const
virtual Bool_t	TObject::IsSortable() const
Bool_t	TObject::IsZombie() const
virtual void	TObject::ls(Option_t* option = "") const
void	TObject::MayNotUse(const char* method) const
virtual Bool_t	TObject::Notify()
void	TObject::Obsolete(const char* method, const char* asOfVers, const char* removedFromVers) const
static void	TObject::operator delete(void* ptr)
static void	TObject::operator delete(void* ptr, void* vp)
static void	TObject::operator delete[](void* ptr)
static void	TObject::operator delete[](void* ptr, void* vp)
void*	TObject::operator new(size_t sz)
void*	TObject::operator new(size_t sz, void* vp)
void*	TObject::operator new[](size_t sz)
void*	TObject::operator new[](size_t sz, void* vp)
TGenPhaseSpace&	operator=(const TGenPhaseSpace& gen)
virtual void	TObject::Paint(Option_t* option = "")
virtual void	TObject::Pop()
virtual void	TObject::Print(Option_t* option = "") const
virtual Int_t	TObject::Read(const char* name)
virtual void	TObject::RecursiveRemove(TObject* obj)
void	TObject::ResetBit(UInt_t f)
virtual void	TObject::SaveAs(const char* filename = "", Option_t* option = "") constMENU
virtual void	TObject::SavePrimitive(ostream& out, Option_t* option = "")
void	TObject::SetBit(UInt_t f)
void	TObject::SetBit(UInt_t f, Bool_t set)
Bool_t	SetDecay(TLorentzVector& P, Int_t nt, const Double_t* mass, Option_t* opt = "")
virtual void	TObject::SetDrawOption(Option_t* option = "")MENU
static void	TObject::SetDtorOnly(void* obj)
static void	TObject::SetObjectStat(Bool_t stat)
virtual void	TObject::SetUniqueID(UInt_t uid)
virtual void	ShowMembers(TMemberInspector&)
virtual void	Streamer(TBuffer&)
void	StreamerNVirtual(TBuffer& ClassDef_StreamerNVirtual_b)
virtual void	TObject::SysError(const char* method, const char* msgfmt) const
Bool_t	TObject::TestBit(UInt_t f) const
Int_t	TObject::TestBits(UInt_t f) const
virtual void	TObject::UseCurrentStyle()
virtual void	TObject::Warning(const char* method, const char* msgfmt) const
virtual Int_t	TObject::Write(const char* name = 0, Int_t option = 0, Int_t bufsize = 0)
virtual Int_t	TObject::Write(const char* name = 0, Int_t option = 0, Int_t bufsize = 0) const

protected:

virtual void	TObject::DoError(int level, const char* location, const char* fmt, va_list va) const
void	TObject::MakeZombie()

private:

Double_t

PDK(Double_t a, Double_t b, Double_t c)

Data Members

public:

enum TObject::EStatusBits {	kCanDelete
	kMustCleanup
	kObjInCanvas
	kIsReferenced
	kHasUUID
	kCannotPick
	kNoContextMenu
	kInvalidObject
};
enum TObject::[unnamed] {	kIsOnHeap
	kNotDeleted
	kZombie
	kBitMask
	kSingleKey
	kOverwrite
	kWriteDelete
};

private:

Double_t	fBeta[3]	betas of decaying particle
TLorentzVector	fDecPro[18]	kinematics of the generated particles
Double_t	fMass[18]	masses of particles
Int_t	fNt	number of decay particles
Double_t	fTeCmTm	total energy in the C.M. minus the total mass
Double_t	fWtMax	maximum weigth

Class Charts

Inheritance Inherited Members Includes Libraries

Function documentation

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

the PDK function

TGenPhaseSpace(const TGenPhaseSpace& gen)

copy constructor

TGenPhaseSpace& operator=(const TGenPhaseSpace& gen)

 Assignment operator

Double_t Generate()

  Generate a random final state.
  The function returns the weigth 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

TLorentzVector * GetDecay(Int_t n)

return Lorentz vector corresponding to decay n

Bool_t 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 dependece
 return value:
 kTRUE:      the decay is permitted by kinematics
 kFALSE:     the decay is forbidden by kinematics

TGenPhaseSpace()

{}

virtual ~TGenPhaseSpace()

{}

Int_t GetNt() const

{ return fNt;}

Double_t GetWtMax() const

{ return fWtMax;}