library: libPhysics
#include "TGenPhaseSpace.h"

TGenPhaseSpace

class description - header file - source file - inheritance tree (.pdf)

class TGenPhaseSpace : public TObject

Inheritance Chart:
TObject
<-
TGenPhaseSpace
 
    private:

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

    public:

                      TGenPhaseSpace()
                      TGenPhaseSpace(const TGenPhaseSpace& gen)
              virtual ~TGenPhaseSpace()
       static TClass* Class()
             Double_t Generate()
      TLorentzVector* GetDecay(Int_t n)
                Int_t GetNt() const
             Double_t GetWtMax() const
      virtual TClass* IsA() const
      TGenPhaseSpace& operator=(const TGenPhaseSpace&)
               Bool_t SetDecay(TLorentzVector& P, Int_t nt, Double_t* mass, Option_t* opt = "")
         virtual void ShowMembers(TMemberInspector& insp, char* parent)
         virtual void Streamer(TBuffer& b)
                 void StreamerNVirtual(TBuffer& b)

Data Members

    private:

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

Class Description

_____________________________________________________________________________________

  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/PhaseSpace.C
Double_t PDK(Double_t a, Double_t b, Double_t c)
the PDK function
TGenPhaseSpace(const TGenPhaseSpace &gen)
copy constructor
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 get using GetDecay(n).
  The maximum weigth can be get using GetWtMax().
TLorentzVector * GetDecay(Int_t n)
return Lorentz vector corresponding to decay n
Bool_t SetDecay(TLorentzVector &P, Int_t nt, Double_t *mass, Option_t *opt)
 input:
 TLorentzVector &P:    decay particle
 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()




Double_t GetWtMax()







Author: Rene Brun, Valerio Filippini 06/09/2000 

Last update: root/physics:$Name:  $:$Id: TGenPhaseSpace.cxx,v 1.11 2006/05/16 08:13:31 brun Exp $









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