$Id: README,v 1.2 2004/06/23 11:28:04 maire Exp $
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Geant4 - an Object-Oriented Toolkit for Simulation in HEP
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MuonProcesses
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This example is intended to check implementation of the processes
of muon interactions: ionization, direct (e+,e-) production,
bremsstrahlung, mu-nuclear interaction.
It allows to compute differential cross sections (as function of the
energy tranfered 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 contains only electromagnetic processes for muon,
adding G4MuNuclearInteraction and seting of upper energy range limit
to 1000 PeV).
Standard (default) and g4v52 (frozen at the release Genat4 v.5.2)
physics can be choosen.
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 crossSection
computed from this.
At EndOfRun, the above results are compared with analytic calculations.
The functions which compute the theoritical crossSections have been
provided by the G4 MEPhI group, and grouped in MuCrossSection class.
5- HISTOGRAMS
The test contains 4 built-in 1D histograms, which are managed by the
HistoManager class and its Messenger.
1 Monte-Carlo relative transferred energy distribution histo
(log10(eps/Emu kin) for knock-on electrons (ionization)
2 -"- direct (e+,e-) pair production
3 -"- bremsstrahlung
4 -"- nuclear interaction
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 anf filled (histo 6 to 9), and the comparison
(G4 divided by theory) is done in histos 11 to 14.
The histograms can be viewed using PAW. See below the note on
ANAPHE+AIDA.
Note that, by default, histograms are disabled. To activate them,
uncomment the flag G4ANALYSIS_USE in GNUmakefile.
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 ?
compile and link to generate an executable
% cd geant4/examples/extended/electromagnetic/MuonProcesses
% gmake
execute MuonProcesses in 'batch' mode from macro files :
% MuonProcesses allproc.mac
execute MuonProcesses in 'interactive mode' with visualization :
% MuonProcesses
Idle> control/execute vis.mac
....
Idle> type your commands
....
Idle> exit
8- Using histograms
-------------------
By default the histograms are not activated. To activate histograms
the environment variable G4ANALYSIS_USE should be defined. For instance
uncomment the flag G4ANALYSIS_USE in GNUmakefile.
To use histograms any of implementations of AIDA interfaces should
be available (see http://aida.freehep.org).
A package including AIDA and extended interfaces also using Python
is PI, available from: http://cern.ch/pi .
Once installed PI or PI-Lite in a specified local area $MYPY, it is
required to add the installation path to $PATH, i.e. for example,
for release 1.2.1 of PI:
setenv PATH ${PATH}:$MYPI/1.2.1/app/releases/PI/PI_1_2_1/rh73_gcc32/bin
CERN users can use the PATH to the LCG area on AFS.
Before compilation of the example it is optimal to clean up old
files:
gmake histclean
gmake
Before running the example the command should be issued:
eval `aida-config --runtime csh`
It is possible to choose the format of the output file with
histograms using UI command:
/testem/histo/setFileType type
The following types are available: hbook, root, xml.
Gabriele Cosmo