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Geant4 - an Object-Oriented Toolkit for Simulation in HEP
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lArCal
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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
20 GeV). These 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
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You can select between 4 Physics Lists: QGSP, LHEP, QGSC, QGSP_BIC_EMY.
The last one is set as default, so that you can test the low-energy
electromagnetic.
The selection is done simply by comment/uncomment a line in the main
lArCal.cc (look for the keyword ***LOOKHERE***).
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 prerunlArcal.mac
- execute Test in 'interactive mode' with visualization
% lArCal
...
Idle> type your commands
...
Idle> exit
6. HISTOGRAMS
--------------
The analysis is performed using the histogramming tools provided by
Geant4. No external dependencies are required.
lArCal produces 4 histograms (saved as fcal.root) 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 --> Total energy deposited (in MeV) in the electromagnetic module
Histo4 --> Total energy deposited (in MeV) in the hadronic module
See their definitions in FCALRunAction.cc
The histograms are saved (default) as a ROOT file. It is possible to save the
histograms in a xml file by editing
include/FCALAnalysisManager.hh
(comment g4root.hh and uncomment g4xml.hh)
Gabriele Cosmo