
     =========================================================
     Geant4 - an Object-Oriented Toolkit for Simulation in HEP
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                            field06 Example
                            ---------------

     This example exercises the capability of tracking massive
     particles in a gravity field.

     Credit goes to Erik Miller (Univ. of Northern British Columbia) and
     Garry Yan (Univ. of Toronto)

**************
*Classes Used*
**************

 1 - main()

    See field06.cc.


 2- GEOMETRY DEFINITION

    As simple world G4Box with a G4UniformGravityField propagating momentum
    (G4EqGravityField) with G4ClassicalRK4(fEquation,8). The example uses the
    default gravity field on the earth's surface: gy = -9.81*m/s/s/c_light.

 3- AN EVENT: THE PRIMARY GENERATOR

    Uses an Ultra Cold Neutron (UCN) and G4ParticleGun with:
    particleEnergy = G4UniformRand()*1e-7*eV

    UCN are launched from (0,0,0) uniform into 4pi

 4- PHYSICS

    The simulation knows of only six particles: G4Neutron, G4Proton, 
    G4Electron, G4AntiNeutrinoE, G4MuonPlus and G4MuonMinus

    RegisterPhysics(new G4StepLimiterPhysics());

    G4StepLimiterPhysics defines G4StepLimiter and G4UserSpecialCuts

 5- HOW TO START ?

   This example handles the program arguments in a new way.
   It can be run with the following optional arguments:
   % field06 [-m macro ] [-u UIsession] [-t nThreads] [-r randomSeed]

   The -t option is available only in multi-threading mode
   and it allows the user to override the Geant4 default number of
   threads. The number of threads can be also set via G4FORCENUMBEROFTHREADS
   environment variable which has the top priority.

        - Execute field06 in 'batch' mode from macro files e.g.
                % field06 -m field06.in > field06.out &

        - Execute field06 in 'interactive' mode with visualization e.g.
                % field06
                ....
                Idle> type your commands, for example:
                Idle> run/beamOn 1
                ....
