| Geant4 Cross Reference |
1 2 ========================================================= 3 Geant4 - an Object-Oriented Toolkit for Simulation in HEP 4 ========================================================= 5 6 lArCal 7 -------- 8 9 This example is intended to simulate the Forward Liquid Argon Calorimeter 10 (FCAL) of the ATLAS Detector at LHC. The goal of the FCAL is to provide 11 a good missing energy determination in the region of very small angles 12 from the beam direction. 13 14 15 1. GEOMETRY DEFINITION 16 ------------------------ 17 18 The liquid Argon calorimeter consists of three modules with the same 19 nominal outer dimensions: an electromagnetic module (made 20 of copper) followed by two hadronic ones (made of tungsten alloy). 21 The corresponding parameters of these modules are defined inside the 22 FCALEMModuleParameters.input and FCALHadModuleParameters.input files. 23 The package contains as well a FCALTestbemSetup class whose geometry is given by 24 FCALTestbeamSetupParameters.input. See these files for details concerning to 25 radius, lenght and angles of the different components. 26 27 28 2. AN EVENT : THE PRIMARY GENERATOR 29 ------------------------------------ 30 31 The primary kinematic consists of a single particle which hits the 32 geometry perpendicular to the input face. The FCALPrimaryGeneratorAction 33 class gives the particle and its energy (by default it is an electron of 34 20 GeV). These parameters can be changed in commands of ParticleGun class 35 inside the macros given in this example. 36 37 The subdirectory data-tracks contains the kinematic files 38 of the particles for different energies (20 GeV, 40 GeV, 60 GeV, 80 GeV, 39 120 GeV and 200 GeV). 40 The information given inside these files are the X, Y, Z and cosX, 41 cosY, cosZ variables for each event. 42 43 A RUN is a set of events. 44 45 46 3. VISUALIZATION 47 ------------------ 48 49 The Visualization Manager is set in the main(). 50 The initialisation of the drawing is done via the command 51 > /control/execute vis.mac 52 53 The detector has a default view which is a transversal view of the geometry. 54 55 The tracks are drawn at the end of event, and erased at the end of run. 56 Optionally the way of drawing the particles can be changed in the 57 TBEVentActionMessenger class. 58 59 60 4. PHYSICS 61 ---------- 62 63 You can select between 4 Physics Lists: QGSP, LHEP, QGSC, QGSP_BIC_EMY. 64 The last one is set as default, so that you can test the low-energy 65 electromagnetic. 66 The selection is done simply by comment/uncomment a line in the main 67 lArCal.cc (look for the keyword ***LOOKHERE***). 68 69 70 5. HOW TO START ? 71 ----------------- 72 73 - compile and link to generate an executable 74 % cd geant4/examples/advanced/lAr_calorimeter 75 % gmake 76 77 - execute the program in 'batch' mode from macro files 78 % lArCal prerunlArcal.mac 79 80 - execute Test in 'interactive mode' with visualization 81 % lArCal 82 ... 83 Idle> type your commands 84 ... 85 Idle> exit 86 87 88 6. HISTOGRAMS 89 -------------- 90 The analysis is performed using the histogramming tools provided by 91 Geant4. No external dependencies are required. 92 93 lArCal produces 4 histograms (saved as fcal.root) which illustrate 94 the final state of the most important variables of the example: 95 96 Histo1 --> Number of tracks out of World 97 Histo2 --> Number of secondary particles 98 Histo3 --> Total energy deposited (in MeV) in the electromagnetic module 99 Histo4 --> Total energy deposited (in MeV) in the hadronic module 100 101 See their definitions in FCALRunAction.cc 102 103 The histograms are saved (default) as a ROOT file. It is possible to save the 104 histograms in a xml file by changing the G4AnalysisManager default file type 105 in the FCALRunAction constructor. 106