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Geant4 - an Object-Oriented Toolkit for Simulation in HEP
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TestEm17
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This example is intended to check implementation of the processes
of muon interactions: ionization, direct (e+,e-) production, mu+mu-
pair production, bremsstrahlung, and mu-nuclear interaction.
It allows to compute differential cross sections (as function of the
energy transfered to secondaries), total cross sections, and to compare
with analytic calculations.
1- GEOMETRY DEFINITION
It is a single box of homogeneous medium.
Two parameters define the geometry :
- the material of the box,
- the (full) size of the box.
The default geometry (1 m of Iron) is constructed in
DetectorConstruction, but the above parameters can be changed
interactively via the commands defined in DetectorMessenger.
2- PHYSICS LIST
The Physics List of the example uses the main physics constructor
(builder) called "local", which includes only muon, pion, and proton
processes under study. As an alternative standard "emstandard_opt0"
and "emstandard_opt4" constructors may be used.
Default energy range for EM processes in this example
is from 100*eV to 1000*PeV.
Optionally "muNucl" builder may be added activating muon-nuclear
inelastic interaction.
3- AN EVENT : THE PRIMARY GENERATOR
The primary kinematic consists of a single particle starting at the edge
of the box. The type of the particle and its energy are set in
PrimaryGeneratorAction (mu+ 10 TeV), and can be changed via the G4
build-in commands of ParticleGun class (see the macros provided with
this example).
4- PHYSICS
The incident particle is a muon. During the tracking, secondary
particles are killed.
The number of interactions are plotted as a function of the energy
transfered to the secondaries.
The total number of interactions is recorded, and the total cross
section computed from this.
At RunAction::EndOfRun(..), the above results are compared with analytical
calculations. The functions computing the theoretical cross sections have been
provided by the G4 MEPhI group, and implemented in MuCrossSections class.
5- HISTOGRAMS
The test contains built-in 1D histograms for muons filled during
Monte Carlo simulation, which are managed by the HistoManager class
and its Messenger:
1 Relative muon transferred energy distribution
(log10(eps/Emu kin) for knock-on electrons (ionization)
2 -"- direct (e+,e-) pair production by muons
3 -"- bremsstrahlung by muons
4 -"- nuclear interaction by muons
5 ionistion for hadrons
6 (e+,e-) pair production by hadrons
7 bremsstrahlung by hadrons
8 direct mu+,mu- pair production by muons
The histos can be activated individually with the command :
/testem/histo/setHisto id nbBins valMin valMax :
min and max values of log10(eps/Emu kin).
At EndOfRun the corresponding histos for analytic calculations are
automatically created and filled (histo 11 to 14, and 18).
One can control the name and the type of the histograms file with
the command:
/testem/histo/setFileName name (default testem17)
6- VISUALIZATION
The Visualization Manager is set in the main().
The initialisation of the drawing is done via the commands
/vis/... in the macro vis.mac. To get visualisation:
> /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.
7- HOW TO START ?
execute TestEm17 in 'batch' mode from macro files :
% TestEm17 allproc.mac
execute TestEm17 in 'interactive mode' with visualization :
% TestEm17
Idle> control/execute vis.mac
....
Idle> type your commands
....
Idle> exit
Gabriele Cosmo