$Id: README,v 1.1 2001/10/11 07:18:17 grichine Exp $
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     Geant4 - an Object-Oriented Toolkit for Simulation in HEP
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                            field03 (based on field01)  
                            -------------------------

    Test for investigation of tracking in magnetic field which is set different
                        depending of selected logical volume

	
 1- GEOMETRY DEFINITION
 
 	The "absorber" is a solid made of a given material.                
 	
 	Three parameters define the absorber :
 	- the material of the absorber,
	- the thickness of an absorber,
 	- the transverse size of the absorber (the input face is a square). 
    
        The volume "World" contains the "absorber". 
        In this test the parameters of the "World" can be changed , too.

 	In addition a transverse uniform magnetic field can be applied.
 	
 	The default geometry is constructed in DetectorConstruction class,
 	but all the parameters can be changed via
 	the commands defined in the DetectorMessenger class.
 	
 2- AN EVENT : THE PRIMARY GENERATOR
 
 	The primary kinematic consists of a single particle which hits the
 	absorber perpendicular to the input face. The type of the particle
 	and its energy are set in the PrimaryGeneratorAction class, and can
 	be changed via the G4 build-in commands of ParticleGun class (see
 	the macros provided with this example).
 	
 	A RUN is a set of events.
 	
 3- DETECTOR RESPONSE

        Here we test G4PAIionisation , G4IonisationByLogicalVolume and 
        transition radiation processes
 
 	A HIT is a record, event per event , of all the 
 	informations needed to simulate and analyse the detector response.
 	
 	In this example a CalorHit is defined as a set of 2 informations:
 	- the total energy deposit in the absorber,
 	- the total tracklength of all charged particles in the absorber,  
 	
 	Therefore  the absorber is declared
 	'sensitive detector' (SD), which means they can contribute to the hit.
 	
 	At the end of a run, from the histogram(s), one can study 
	different physics quantities such as :
                                - angle distribution,
				- energy deposit,
 				- transmission/backscattering,
 				-  ...
        
        The test contains 10 built-in histograms, which can be activated by
        interactive commands (see the macros runxx.mac for details).
        The histograms/plots are in printed form in the corresponding 
        resultxx (for GEANT4) and outxx (for GEANT3) files, and they are
        saved as geant4.plotxx and geant3.plotxx histogram files, too.

        The histogram files can be viewed using PAW e.g with the commands 

                paw> h/file 1 geant4.plot01 or g4.p11
                paw> option stat
                paw> h/pl 1


 				
 4- PHYSICS DEMO
 
 	The particle's type and the physic processes which will be available
 	in this example are set in PhysicsList class.
 	
 	The  messenger classes introduce interactive commands . Using these
        commands the geometry of the detector, the data of the primary
        particle, the limits of the histograms , etc. can be changed.
 	

 5- HOW TO START ?
 
 	- compile and link to generate an executable
 		% cd $G4INSTALL/example/extended/field/field01
 		% gmake
 		
 	- execute field01 in 'batch' mode from macro files e.g.
 		% $(G4INSTALL)/bin/$(G4SYSTEM)/field01   run11.mac
		
 	- execute field01 in 'interactive' mode with visualization e.g.
 		% $(G4INSTALL)/bin/$(G4SYSTEM)/field01
		....
		Idle> type your commands
		....
		
 6- GEANT4/GEANT3/exp.data comparison

        A GEANT4/GEANT3/exp. data comparison is given here for a few cases.
        
        The GEANT4 results can be found in the results/ directory, the resultxx
        output was obtained with the runxx.mac macro.

        The relevant part of the GEANT3 code is in the geant3/ directory
        together with the runxx.dat input files. The outputs of the GEANT3 runs
        geant3/results subdirectory.
	
        In order to make an executable of GEANT3 the gmakeB command should be
        used in the geant3/ subdirectory.To run this executable with a given
        input file the input file name should be given when it is being asked
        by the program.(see geant3/README)
 		
 	The expdata/  directory contains some information
        on the experimental data. 
 	  
 	
 List of the built-in histograms
 -------------------------------

        1.   number of (tracking) steps/event
        2.   energy deposit distribution in the absorber (in MeV)
        3.   angle distribution of the primary particle at the exit
             of the absorber (deg)
        4.   distribution of the lateral displacement at exit(mm)
        5.   kinetic energy of the transmitted primaries (MeV)
        6.   angle distribution of the backscattered primaries (deg)
        7.   kinetic energy of the backscattered primary particles (MeV)
        8.   kinetic energy of the charged secondary particles (MeV)
        9.   z distribution of the secondary charged vertices (mm)
       10.   kinetic energy of the photons escaping the absorber (MeV)