$Id: README 93739 2015-10-30 11:04:09Z gcosmo $
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     =========================================================
     Geant4 - an Object-Oriented Toolkit for Simulation in HEP
     =========================================================

                            TestEm6 
                            -------
     This example is intended to test the processes of gamma conversion
     to a pair of muons and annihilation of positrons with atomic
     electrons to a pair of muons.
	
 1- GEOMETRY DEFINITION
 
     The geometry consists of a single block of a homogenous material.
     	
     Two parameters define the geometry :
      - the material of the box,
      - the (full) size of the box.
     The default is 500 m of iron.
     	 	
     In addition a transverse uniform magnetic field can be applied.
 	
     The default geometry is constructed in DetectorConstruction class,
     but all of the above parameters can be changed interactively via
     the commands defined in the DetectorMessenger class.
 	
 2- PHYSICS LIST

     Physics Lists are based on modular design. Several modules are 
     instantiated:
     1. Transportation
     2. EM physics
     3. Decays
     4. StepMax - for step limitation
  
     The electromagnetic physics is chosen from one of the Geant4 EM
     physics constructors in the physics_list library.

     Cross sections can be enhanced (see below).
 	 
 3- AN EVENT : THE PRIMARY GENERATOR
 
     The primary kinematic consists of a single particle which hits the
     block perpendicular to the input face. The type of the particle
     and its energy are set in the PrimaryGeneratorAction class, and can
     changed via the G4 build-in commands of G4ParticleGun class (see
     the macros provided with this example).
     The default is a Gamma of 100 TeV.
     	
     In addition one can choose randomly the impact point of the incident
     particle. The corresponding interactive command is built in
     PrimaryGeneratorMessenger class.
	 	
     A RUN is a set of events.
 				
 4- VISUALIZATION
 
     The Visualization Manager is set in the main() (see TestEm6.cc).
     The initialisation of the drawing is done via the command
     > /control/execute vis.mac
 	
     The detector has a default view which is a longitudinal view of the box.
 	
     The tracks are drawn at the end of event, and erased at the end of run.
     Optionally one can choose to draw all particles, only the charged ones,
     or none. This command is defined in EventActionMessenger class.

 5- PHYSICS DEMO

     The particle's type and the physics processes which will be available
     in this example are set in PhysicsList class.

     In addition a build-in interactive command (/process/inactivate procname)
     allows to activate/inactivate the processes one by one.

     The threshold for producing secondaries can be changed.
     eg: /run/particle/setCut 100 micrometer
         /run/initialize
	 
     To visualize the GammaConversionToMuons :
        /control/execute run01.mac
        /control/execute vis.mac
        /run/beamOn
		 
     To visualize the AnnihiToMuPair :
        /control/execute run11.mac
        /control/execute vis.mac
        /run/beamOn
		  	
 6- HOW TO START ?
 
     - execute Test  in 'batch' mode from macro files
 	% TestEm6    run01.mac
 		
     - execute Test  in 'interactive mode' with visualization
 	% TestEm6 
 		....
 	Idle> type your commands
 		....
 	Idle> exit
 
 7- HOW TO INCREASE STATISTICS ON gamma -> mu+mu- ?
 
     The processes of gamma -> mu+mu-  and e+e- -> mu+mu-
     have a low cross section but can be important
     for leakage through thick absorbers and calorimeters.
     Straight forward simulation will be quite time consuming.
     To make the processes more visible, the cross section can be
     artificially increased by some factor (here 1000)
     using the commands  (only effective after  /run/initialize)

     /testem/phys/SetGammaToMuPairFac  1000
     /testem/phys/SetAnnihiToMuPairFac 1000
 
	
 8- HISTOGRAMS
 
  Testem6 produces 6 histograms which illustrate the final state of 
  the GammaConversionToMuons process. See their definitions in RunAction.cc   
	
  By default the histograms are saved as testem6.root

  The format of the histogram file can be : root (default), xml, csv,
  by selecting g4nnn.hh in RunAction.hh