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Geant4 - an Object-Oriented Toolkit for Simulation in HEP
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monopole
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V.Ivanchenko, M.Vladymyrov
CERN, Geneva, Switzerland
Lebedev Physical Institute, Moscow, Russia
This example is devoted to the energy deposited by classical magnetic
monopole.
1- GEOMETRY DEFINITION
The geometry consists of a single block of a homogenous material,
placed in a world.
Four parameters define the geometry :
- the material of the box
- the thickness of the box
- the tranverse dimension of the box
- the maximal step size in target
The default is 10 cm of alumunium, step is limited by 5mm.
Equivalent UI commands are following:
/testex/det/setMat G4_Al
/testex/det/sizeX 10 cm
/testex/det/sizeYZ 5 cm
/testex/det/setStepSize 5 mm
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.
In addition, a global, uniform, and transverse magnetic field can be applied
via G4MonopoleFieldSetup class, with the default z-value 0.2 tesla.
This value can be changed via UI command:
/testex/fld/setField 0.2 tesla
2- PHYSICS LIST
The physics list includes standard FTFP_BERT physics and the additional builder
or monopole physics.
To define monopole parameters an extra string should be provided via
the program arguments:
./monopole -s '2 0 200 GeV' # in the interactive mode
./monopole -m file.mac -s '2 0 200 GeV' # in the batch mode
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 ParticleGun class (see
the macros provided with this example).
The default is monopole 100 GeV.
4- VISUALIZATION
The Visualization Manager is set in the main() for interactive session,
the initial parameters of the program are defined in the init_vis.mac macro
which then executes the visualisation macro, 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.
5- HOW TO RUN ?
This example handles the program arguments in a similar way as the basic
B4 example.
It can be run with the following optional arguments:
% ./monopole [-m macro ] [-s setupMonopole] [-t nThreads]
The -s option was already explained in the Physics list section.
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 program in the 'batch' mode from macro files
% ./monopole -m monopole.in [-s setupMonopole]
- Execute program in the 'interactive mode' with visualization
% ./monopole [-s setupMonopole]
....
Idle> type your commands
....
Idle> exit
6- HISTOGRAMS
The result is five histograms:
- Monopole eneregy deposition in current material
- dedx for proton
- dedx for monopole
- range for proton in current material
- range for monopole in current material
The histogram is saved in Root file.
Limit of bin size can be set with testex/run/binSize (default 5mm). Real size
is chosen as a minimal between this and step limit (see Geometry section)
Gabriele Cosmo