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StGenParticle Class Referenceabstract

Abstract base class for particles related to common /HEPEVT/. More...

#include <StGenParticle.h>

Inheritance diagram for StGenParticle:
StGimParticle StHepParticle

Public Member Functions

virtual void Print (const char *opt="") const
virtual int GetStatusCode () const =0
virtual int GetPdgCode () const
virtual int GetGeaCode () const
virtual const StGenParticleGetMother (int i=0) const =0
virtual const StGenParticleGetDaughter (int i) const =0
virtual double GetCalcMass () const
virtual double GetMass () const =0
virtual int GetNDaughters () const =0
virtual double GetWeight () const
virtual void Momentum (double p4[4]) const =0
virtual void Vertex (double v[3]) const =0
virtual double Time () const =0
int IsPrimary () const
int IsFinal () const
double R () const
double Rho () const
double P () const
double Pt () const
double Energy () const
double Eta () const
double Phi () const
double Theta () const

Protected Member Functions

 StGenParticle (int idx=0)
void SetIdx (int idx)
int GetIdx () const

Protected Attributes

int mIdx

Detailed Description

Abstract base class for particles related to common /HEPEVT/.

Victor Perev

StGenParticle and derived StHepParticle,StGimParticle are based on HEPEVT standard ( Description of HEPEVT follows

NMXHEP: maximum numbers of entries (particles) that can be stored in the common block. The default value of 4000 can be changed via the parameter construction. In the translation, it is checked that this value is not exceeded.

NEVHEP: is normally the event number, but may have special meanings, according to the description below:

> 0 : event number, sequentially increased by 1 for each call to the main event generation routine, starting with 1 for the first event generated. = 0 : for a program which does not keep track of event numbers, as some of the PYTHIA routines. = -1 : special initialization record; not used by PYTHIA. = -2 : special final record; not used by PYTHIA.

NHEP: the actual number of entries stored in the current event. These are found in the first NHEP positions of the respective arrays below. Index IHEP, 1$$IHEP$$NHEP, is used below to denote a given entry.

ISTHEP(IHEP): status code for entry IHEP, with the following meanings:

= 0 : null entry. = 1 : an existing entry, which has not decayed or fragmented. This is the main class of entries, which represents the `final state' given by the generator. = 2 : an entry which has decayed or fragmented and is therefore not appearing in the final state, but is retained for event history information. = 3 : a documentation line, defined separately from the event history. This could include the two incoming reacting particles, etc. = 4 - 10 : undefined, but reserved for future standards. = 11 - 200 : at the disposal of each model builder for constructs specific to his program, but equivalent to a null line in the context of any other program. = 201 - : at the disposal of users, in particular for event tracking in the detector.

IDHEP(IHEP) : particle identity, according to the PDG standard. The four additional codes 91-94 have been introduced to make the event history more legible, see section [*] and the MSTU(16) description of how daughters can point back to them.

JMOHEP(1,IHEP) : pointer to the position where the mother is stored. The value is 0 for initial entries.

JMOHEP(2,IHEP) : pointer to position of second mother. Normally only one mother exists, in which case the value 0 is to be used. In PYTHIA, entries with codes 91-94 are the only ones to have two mothers. The flavour contents of these objects, as well as details of momentum sharing, have to be found by looking at the mother partons, i.e. the two partons in positions JMOHEP(1,IHEP) and JMOHEP(2,IHEP) for a cluster or a shower system, and the range JMOHEP(1,IHEP)-JMOHEP(2,IHEP) for a string or an independent fragmentation parton system.

JDAHEP(1,IHEP) : pointer to the position of the first daughter. If an entry has not decayed, this is 0.

JDAHEP(2,IHEP) : pointer to the position of the last daughter. If an entry has not decayed, this is 0. It is assumed that daughters are stored sequentially, so that the whole range JDAHEP(1,IHEP)-JDAHEP(2,IHEP) contains daughters. This variable should be set also when only one daughter is present, as in ${K}^0 {K}_{{S}}^0$ decays, so that looping from the first daughter to the last one works transparently. Normally daughters are stored after mothers, but in backwards evolution of initial-state radiation the opposite may appear, i.e. that mothers are found below the daughters they branch into. Also, the two daughters then need not appear one after the other, but may be separated in the event record.

PHEP(1,IHEP) : momentum in the $x$ direction, in GeV/$c$.

PHEP(2,IHEP) : momentum in the $y$ direction, in GeV/$c$.

PHEP(3,IHEP) : momentum in the $z$ direction, in GeV/$c$.

PHEP(4,IHEP) : energy, in GeV.

PHEP(5,IHEP) : mass, in GeV/$c^2$. For space-like partons, it is allowed to use a negative mass, according to PHEP(5,IHEP) $ = -{-m^2}$.

VHEP(1,IHEP) : production vertex $x$ position, in mm.

VHEP(2,IHEP) : production vertex $y$ position, in mm.

VHEP(3,IHEP) : production vertex $z$ position, in mm.

VHEP(4,IHEP) : production time, in mm/$c$ ( $ 3.33 10^{-12}$ s).

Definition at line 133 of file StGenParticle.h.

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