Gabriele Cosmo
135 lines
4.8 KiB
Plaintext
135 lines
4.8 KiB
Plaintext
$Id: README,v 1.5 2002/12/12 12:48:15 maire Exp $
|
|
-------------------------------------------------------------------
|
|
|
|
=========================================================
|
|
Geant4 - an Object-Oriented Toolkit for Simulation in HEP
|
|
=========================================================
|
|
|
|
TestEm6
|
|
-------
|
|
This example is intended to test the process of
|
|
gamma conversion to a pair of muons.
|
|
To make this process more visible, the usually much more frequent
|
|
gamma conversion to a pair of electrons is not selected in the
|
|
physics list.
|
|
|
|
1- GEOMETRY DEFINITION
|
|
|
|
The geometry consists of a single block of a homogenous material.
|
|
|
|
Two parameters define the geometry :
|
|
- the material of the box,
|
|
- the (full) size of the box.
|
|
The default is 500 m of iron.
|
|
|
|
In addition a transverse uniform magnetic field can be applied.
|
|
|
|
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.
|
|
|
|
2- PHYSICS LIST
|
|
|
|
The particle list is the one of novice/exampleN03.
|
|
The physics list contains the 'standard' electromagnetic processes,
|
|
and decay.
|
|
|
|
For Gamma, only the GammaConversionToMuons has been registered.
|
|
Futhermore, a high production cut (1 km, which gives infinity in energy)
|
|
prevent any production of delta-electrons from ionization or gamma
|
|
from bremsstrahlung.
|
|
|
|
|
|
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 a Gamma of 100 TeV.
|
|
|
|
In addition one can choose randomly the impact point of the incident
|
|
particle. The corresponding interactive command is built in
|
|
PrimaryGeneratorMessenger class.
|
|
|
|
A RUN is a set of events.
|
|
|
|
|
|
4- VISUALIZATION
|
|
|
|
The Visualization Manager is set in the main().
|
|
The initialisation of the drawing is done via the command
|
|
> /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.
|
|
Optionaly one can choose to draw all particles, only the charged one,
|
|
or none. This command is defined in EventActionMessenger class.
|
|
|
|
5- PHYSICS DEMO
|
|
|
|
The particle's type and the physic processes which will be available
|
|
in this example are set in PhysicsList class.
|
|
|
|
In addition a build-in interactive command (/process/inactivate proname)
|
|
allows to activate/inactivate the processes one by one.
|
|
|
|
The threshold for producing secondaries can be changed.
|
|
eg: /run/particle/setCut 100 micrometer
|
|
/run/initialize
|
|
|
|
6- HOW TO START ?
|
|
|
|
- compile and link to generate an executable
|
|
% cd geant4/examples/extended/electromagnetic/TestEm6
|
|
% gmake
|
|
|
|
- execute Test in 'batch' mode from macro files
|
|
% TestEm6 run01.mac
|
|
|
|
- execute Test in 'interactive mode' with visualization
|
|
% TestEm6
|
|
....
|
|
Idle> type your commands
|
|
....
|
|
Idle> exit
|
|
|
|
7- HISTOGRAMS
|
|
|
|
Testem6 produces 6 histograms (saved as testem6.paw) which illustrate
|
|
the final state of the GammaConversionToMuons process.
|
|
See their definitions in RunAction.cc
|
|
|
|
Note that histograms are disabled via the flag G4NOHIST in GNUmakefile.
|
|
|
|
8- Using the Anaphe implementation of the AIDA 3.0 histograms:
|
|
--------------------------------------------------------------
|
|
|
|
In order to use the Anaphe implementation of the AIDA 3.0 interfaces,
|
|
the 'aida-config' command (which is used in the GNUmakefile) is
|
|
available at:
|
|
/afs/cern.ch/sw/lhcxx/share/LHCXX/latest/scripts/aida-config
|
|
|
|
In order to run the executable, you need to source the following
|
|
script (once):
|
|
$HOME/bin/setupAnaphe.csh (or $HOME/bin/setupAnaphe)
|
|
|
|
At cern 'setupAnaphe' is available at:
|
|
/afs/cern.ch/sw/lhcxx/share/LHCXX/latest/scripts/setupAnaphe.csh
|
|
(or /afs/cern.ch/sw/lhcxx/share/LHCXX/latest/scripts/setupAnaphe)
|
|
|
|
|
|
9- HOW TO INCREASE STATISTICS ON gamma -> mu+mu- ?
|
|
|
|
The process of gamma -> mu+mu- has a low cross section but can be important
|
|
for leakage through thick absorbers and calorimeters.
|
|
Straight forward simulation will be quite time consuming.
|
|
To make the process more visible, the cross section can be artificially
|
|
increased by some factor (here 1000) using the command
|
|
(only effective after /run/initialize)
|
|
|
|
/run/process/setGammaToMuPairFac 1000
|
|
|