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0001 -------------------------------------------------------------------
0002
0003 =========================================================
0004 Geant4 - an Object-Oriented Toolkit for Simulation in HEP
0005 =========================================================
0006
0007 TestEm6
0008 -------
0009 This example is intended to test the processes of gamma conversion
0010 to a pair of muons and annihilation of positrons with atomic
0011 electrons to a pair of muons.
0012
0013 1- GEOMETRY DEFINITION
0014
0015 The geometry consists of a single block of a homogenous material.
0016
0017 Two parameters define the geometry :
0018 - the material of the box,
0019 - the (full) size of the box.
0020 The default is 500 m of iron.
0021
0022 In addition a transverse uniform magnetic field can be applied.
0023
0024 The default geometry is constructed in DetectorConstruction class,
0025 but all of the above parameters can be changed interactively via
0026 the commands defined in the DetectorMessenger class.
0027
0028 2- PHYSICS LIST
0029
0030 Physics Lists are based on modular design. Several modules are
0031 instantiated:
0032 1. Transportation
0033 2. EM physics
0034 3. Decays
0035 4. StepMax - for step limitation
0036
0037 The electromagnetic physics is chosen from one of the Geant4 EM
0038 physics constructors in the physics_list library.
0039
0040 Cross sections can be enhanced (see below).
0041
0042 3- AN EVENT : THE PRIMARY GENERATOR
0043
0044 The primary kinematic consists of a single particle which hits the
0045 block perpendicular to the input face. The type of the particle
0046 and its energy are set in the PrimaryGeneratorAction class, and can
0047 changed via the G4 build-in commands of G4ParticleGun class (see
0048 the macros provided with this example).
0049 The default is a Gamma of 100 TeV.
0050
0051 In addition one can choose randomly the impact point of the incident
0052 particle. The corresponding interactive command is built in
0053 PrimaryGeneratorMessenger class.
0054
0055 A RUN is a set of events.
0056
0057 4- VISUALIZATION
0058
0059 The Visualization Manager is set in the main() (see TestEm6.cc).
0060 The initialisation of the drawing is done via the command
0061 > /control/execute vis.mac
0062
0063 The detector has a default view which is a longitudinal view of the box.
0064
0065 The tracks are drawn at the end of event, and erased at the end of run.
0066 Optionally one can choose to draw all particles, only the charged ones,
0067 or none. This command is defined in EventActionMessenger class.
0068
0069 5- PHYSICS DEMO
0070
0071 The particle's type and the physics processes which will be available
0072 in this example are set in PhysicsList class.
0073
0074 In addition a build-in interactive command (/process/inactivate procname)
0075 allows to activate/inactivate the processes one by one.
0076
0077 The threshold for producing secondaries can be changed.
0078 eg: /run/particle/setCut 100 micrometer
0079 /run/initialize
0080
0081 To visualize the GammaConversionToMuons :
0082 /control/execute run01.mac
0083 /control/execute vis.mac
0084 /run/beamOn
0085
0086 To visualize the AnnihiToMuPair :
0087 /control/execute run11.mac
0088 /control/execute vis.mac
0089 /run/beamOn
0090
0091 Other macros:
0092 - run02.mac: the final state of the GammaConversionToMuons
0093 - run12.mac: test on carbon target with biasing of cross section
0094
0095 6- HOW TO START ?
0096
0097 - execute Test in 'batch' mode from macro files
0098 % TestEm6 run01.mac
0099
0100 - execute Test in 'interactive mode' with visualization
0101 % TestEm6
0102 ....
0103 Idle> type your commands
0104 ....
0105 Idle> exit
0106
0107 7- HOW TO INCREASE STATISTICS ON gamma -> mu+mu- ?
0108
0109 The processes of gamma -> mu+mu- and e+e- -> mu+mu-
0110 have a low cross section but can be important
0111 for leakage through thick absorbers and calorimeters.
0112 Straight forward simulation will be quite time consuming.
0113 To make the processes more visible, the cross section can be
0114 artificially increased by some factor (here 1000)
0115 using the commands (only effective after /run/initialize)
0116
0117 /testem/phys/SetGammaToMuPairFac 1000
0118 /testem/phys/SetAnnihiToMuPairFac 1000
0119
0120
0121 8- HISTOGRAMS
0122
0123 Testem6 produces 6 histograms, h1 - h6, which illustrate
0124 the final state of the GammaConversionToMuons. The histograms are produced
0125 with run02.mac and can be displayed with the ROOT macro plotHisto.C.
0126
0127 The remaining histograms h7 - h16 show various cross sections and h17 the ratio
0128 of eeToHadr/eeToMu, see their definitions in RunAction.cc
0129
0130 By default the histograms are saved as testem6.root
0131
0132 The format of the histogram file can be : root (default), xml, csv,
0133 by selecting the analysis manager default file type in RunAction.cc
