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     Geant4 - an Object-Oriented Toolkit for Simulation in HEP
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                                 HADR01

            A.Bagulya, I.Gudowska, V.Ivanchenko, N.Starkov
                       CERN, Geneva, Switzerland
            Karolinska Institute & Hospital, Stockholm, Sweden
               Lebedev Physical Institute, Moscow, Russia


This example application is based on the application IION developed for
simulation of proton or ion beam interaction with a water target. Different 
aspects of beam target interaction are demonstrating in the example including 
longitudinal profile of energy deposition, spectra of secondary  particles,
spectra of particles leaving the target. The results are presenting in a form
of average numbers and histograms. 


                           GEOMETRY

The Target volume is a cylinder placed inside Check cylindrical volume. The 
Check volume is placed inside the World volume. The radius and the length of
the Check volume are 1 mm larger than the radius and the length of the Target.
The material of the Check volume is the same as the World material.  The World
volume has the sizes 10 mm larger than that of the Target volume.  Any material
from the Geant4 database can be defined. The default World  material is
G4Galactic and the default  Target material is aluminum. The Target is
subdivided on number of equal slices. Following UI commands are available to
modify the geometry:

/testhadr/TargetMat     G4_Pb
/testhadr/WorldMat      G4_AIR
/testhadr/TargetRadius  10 mm
/testhadr/TargetLength  20 cm
/testhadr/NumberDivZ    200

Beam direction coincides with the target axis and is Z axis in the global
coordinate system. The beam starts 5 mm in front of the target. G4ParticleGun
is used as a primary generator. The energy and the type of the beam can be
defined via standard UI commands

/gun/energy   15 GeV
/gun/particle proton

Default beam position is -(targetHalfLength + 5*mm) and direction along Z axis.
Beam position and direction can be changed by gun UI commands:

/gun/position  1 10 3 mm
/gun/direction 1 0 0

however, position command is active only if before it the flag is set

/testhadr/DefaultBeamPosition false   
 
                           SCORING

The scoring is performed with the help of UserStackingAction class and two
sensitive detector  classes: one associated with a target slice, another with
the Check volume. Each secondary particle is scored by the StackingAction.  In
the StackingAction it is also possible to kill all or one type of secondary 
particles 

/testhadr/Kill             neutron
/testhadr/KillAllSecondaries  

To control running the following options are available:

/testhadr/PrintModulo      100
/testhadr/DebugEvent       977

The last command selects an events, for which "/tracking/verbose 2" level
of printout is established.


                           PHYSICS

PhysicsList of the application uses reference Phsyics Lists or its components, 
which are distributed with Geant4 in /geant4/physics_lists subdirectory.

The reference Physics List name may be defined in the 3d argument of the 
run command: 

Hadr01 my.macro QGSP_BERT   

If 3d argument is not set then the PHYSLIST environment variable is checked. 
If both are not defined then reference Phsyics Lists is not instantiated, 
instead the local Physics List is used which is built from components using 
UI interface. The choice of the physics is provided by the UI command:

/testhadr/Physics     QGSP_BIC

To see the list of available configurations with UI one can use

/testhadr/ListPhysics

The cuts for electromagnetic physics can be established via

/testhadr/CutsAll       1 mm
/testhadr/CutsGamma   0.1 mm
/testhadr/CutsEl      0.2 mm
/testhadr/CutsPos     0.3 mm
/testhadr/CutsProt    0.6 mm

Note that testhadr UI commands are not available in the case when PHYSLIST 
environment variable is defined. 


                          VISUALIZATION

For interactive mode G4 visualization options and variables should be
defined, then the example should be recompiled:

gmake visclean
gmake


                          HISTOGRAMS

There are built in histograms. The 1st one (idx=0, id="1") scores energy
deposition along the target. Histograms "22", "23", "24", "25" scores
energy deposition per particle type.
 
All other histograms are provided in decimal logarithmic scale (log10(E/MeV),
where E is secondary particle energy at production

It is possible to change scale and output file name using UI commands:

/testhadr/histo/fileName name
/testhadr/histo/setHisto idx nbins vmin vmax unit

Only ROOT histograms are available.

All histograms are normalized to the number of events.
