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Geant4 - an Object-Oriented Toolkit for Simulation in HEP
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lArCal
--------
This example is intended to simulate the Forward Liquid Argon Calorimeter
(FCAL) of the ATLAS Detector at LHC. The goal of the FCAL is to provide
a good missing energy determination in the region of very small angles
from the beam direction.
1. GEOMETRY DEFINITION
------------------------
The liquid Argon calorimeter consists of three modules with the same
nominal outer dimensions: an electromagnetic module (made
of copper) followed by two hadronic ones (made of tungsten alloy).
The corresponding parameters of these modules are defined inside the
FCALEMModuleParameters.input and FCALHadModuleParameters.input files.
The package contains as well a FCALTestbemSetup class whose geometry is given by
FCALTestbeamSetupParameters.input. See these files for details concerning to
radius, lenght and angles of the different components.
2. AN EVENT : THE PRIMARY GENERATOR
------------------------------------
The primary kinematic consists of a single particle which hits the
geometry perpendicular to the input face. The FCALPrimaryGeneratorAction
class gives the particle and its energy (by default it is an electron of
80 GeV). Theses parameters can be changed in commands of ParticleGun class
inside the macros given in this example.
The subdirectory data-tracks contains the kinematic files
of the particles for different energies (20 GeV, 40 GeV, 60 GeV, 80 GeV,
120 GeV and 200 GeV).
The information given inside these files are the X, Y, Z and cosX,
cosY, cosZ variables for each event.
A RUN is a set of events.
3. 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 transversal view of the geometry.
The tracks are drawn at the end of event, and erased at the end of run.
Optionally the way of drawing the particles can be changed in the
TBEVentActionMessenger class.
4. PHYSICS DEMO
-----------------
The particle's type and the physic processes which will be available
in this example are set in FCALPhysicsList 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
5. HOW TO START ?
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- compile and link to generate an executable
% cd geant4/examples/advanced/lAr_calorimeter
% gmake
- execute the program in 'batch' mode from macro files
% lArcal prerunlAr.mac
- execute Test in 'interactive mode' with visualization
% lArcal
....
Idle> type your commands
....
Idle> exit
6. HISTOGRAMS
--------------
lArcal produces 4 histograms (saved as fcal.paw) which illustrate
the final state of the most important variables of the example:
Histo1 --> Number of tracks out of World
Histo2 --> Number of secondary particles
Histo3 --> Electromagnetic Energy deposit in the EMModule
Histo4 --> Hadronic Energy deposit in the HadModule
The example generates 3 ntuples too which contains the same information
than the histograms.
See their definitions in FCALAnalysisManager.cc
Note that histograms are disabled via the flag G4ANALYSIS_USE in GNUmakefile.
7. Using the Anaphe implementation of the AIDA 3.0 histograms:
---------------------------------------------------------------
In order to use the new Anaphe implementation of the AIDA interfaces,
prepare some environment variables by source-ing one of the following
startup scripts.
# This example has been developed and tested with the gcc-2.95.2 compiler:
----------
o Set up the environment variable: G4ANALYSIS_USE 1
o setenv PATH ${PATH}:/afs/cern.ch/sw/lhcxx/specific/redhat73/gcc-2.95.2/5.0.5/bin
o source /afs/cern.ch/sw/lhcxx/share/LHCXX/5.0.5/install/sharedstart.csh or .ch
o ln -s /afs/cern.ch/sw/lhcxx/share/LHCXX/5.0.5/scripts/* ~/bin/.
(This has to be made only once)
After this, you will have access to the last 'aida-config' command which
is used in the GNUmakefile.
Gabriele Cosmo