class AliGenGeVSim: public AliGenerator

  Default constructor

  Standard Constructor.

  models - thermal model to be used:
          1    - deconvoluted pt and Y source
          2,3  - thermalized sphericaly symetric sources
          4    - thermalized source with expansion
          5    - custom model defined in TF2 object named "gevsimPtY"
          6    - custom model defined by two 1D histograms
          7    - custom model defined by 2D histogram

  psi   - reaction plane in degrees
  isMultTotal - multiplicity mode
                kTRUE - total multiplicity (default)
                kFALSE - dN/dY at midrapidity

  Default Destructor

  Removes TObjArray keeping list of registered particle types

 private function used by Generate()

 Check bounds of Pt, Rapidity and Azimuthal Angle of a track
 Used only when generating particles from a histogram

 private function used by Generate()

 Check bounds of a total momentum and theta of a track

 private function

 Initalizes formulas used in GeVSim.

 Adds new type of particles.

 Parameters are defeined in AliGeVSimParticle object
 This method has to be called for every particle type

 private function
 Finds Scallar for a given parameter.
 Function used in event-by-event mode.

 There are two types of scallars: deterministic and random
 and they can work on either global or particle type level.
 For every variable there are four scallars defined.

 Scallars are named as folowa
 deterministic global level : "gevsimParam"        (eg. "gevsimTemp")
 deterinistig type level    : "gevsimPdgParam"     (eg. "gevsim211Mult")
 random global level        : "gevsimParamRndm"    (eg. "gevsimMultRndm")
 random type level          : "gevsimPdgParamRndm" (eg. "gevsim-211V2Rndm");

 Pdg - code of a particle type in PDG standard (see: http://pdg.lbl.gov)
 Param - parameter name. Allowed parameters:

 "Temp"   - inverse slope parameter
 "SigmaY" - rapidity width - for model (1) only
 "ExpVel" - expansion velocity - for model (4) only
 "V1"     - directed flow
 "V2"     - elliptic flow
 "Mult"   - multiplicity

 private function used by Generate()

 Retermines Reaction Plane angle and set this value
 as a parameter [0] in fPhiFormula

 Note: if "gevsimPsiRndm" function is found it override both
       "gevsimPhi" function and initial fPsi value

 Private, helper function used by Generate()

 Returns total multiplicity to dN/dY ration using current distribution.
 The function have to be called after setting distribution and its
 parameters (like temperature).

 Private function used by Generate()

 Configure a formula for a given particle type and model Id (in fModel).
 If custom formula or histogram was selected the function tries
 to find it.

 The function implements naming conventions for custom distributions names

 Private function used by Generate()

 Returns random values of Pt and Y corresponding to selected
 distribution.

 Standard AliGenerator initializer.
 does nothing

 Standard AliGenerator function
 This function do actual job and puts particles on stack.