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     Geant4 - an Object-Oriented Toolkit for Simulation in HEP
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                            userPrimaryGenerator 
                            --------------------
		
 The example shows how to create a primary event including several vertices and 
 several primary particles per vertex

 1- Geometry construction
    ---------------------

 It is a simple box which represents an 'infinite' homogeneous medium.
  
 2- Physics list
    ------------

 PhysicsList.cc defines only geantino and transportation process.
         	
 3- Primary generator : several vertices and particles per event
    ------------------------------------------------------------

 vertex A and particle 1 : a geantino uniformly randomized on a cylinder surface.
 vertex B and particles 2 and 3 : symetric to vertex A.

 4- Visualisation
    -------------
 
 Visualization Manager is set in the main().
 Initialisation of the drawing is done via the commands
 /vis/.. in the macro vis.mac. This macro is automatically read from the main 
 in case of interactive running mode.
 
 5- How to start ?
    --------------
 
  - execute basic in 'batch' mode from macro files
	% basic   run1.mac

  - execute basic in 'interactive mode' with visualization
	% basic
	....
	Idle>      ---> type your commands. For instance:
	Idle> /run/beamOn 1
	....
	Idle> exit