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1 -------------------------------------------------------------------
2
3 =========================================================
4 Geant4 - an Object-Oriented Toolkit for Simulation in HEP
5 =========================================================
6
7 TestEm6
8 -------
9 This example is intended to test the processes of gamma conversion
10 to a pair of muons and annihilation of positrons with atomic
11 electrons to a pair of muons.
12
13 1- GEOMETRY DEFINITION
14
15 The geometry consists of a single block of a homogenous material.
16
17 Two parameters define the geometry :
18 - the material of the box,
19 - the (full) size of the box.
20 The default is 500 m of iron.
21
22 In addition a transverse uniform magnetic field can be applied.
23
24 The default geometry is constructed in DetectorConstruction class,
25 but all of the above parameters can be changed interactively via
26 the commands defined in the DetectorMessenger class.
27
28 2- PHYSICS LIST
29
30 Physics Lists are based on modular design. Several modules are
31 instantiated:
32 1. Transportation
33 2. EM physics
34 3. Decays
35 4. StepMax - for step limitation
36
37 The electromagnetic physics is chosen from one of the Geant4 EM
38 physics constructors in the physics_list library.
39
40 Cross sections can be enhanced (see below).
41
42 3- AN EVENT : THE PRIMARY GENERATOR
43
44 The primary kinematic consists of a single particle which hits the
45 block perpendicular to the input face. The type of the particle
46 and its energy are set in the PrimaryGeneratorAction class, and can
47 changed via the G4 build-in commands of G4ParticleGun class (see
48 the macros provided with this example).
49 The default is a Gamma of 100 TeV.
50
51 In addition one can choose randomly the impact point of the incident
52 particle. The corresponding interactive command is built in
53 PrimaryGeneratorMessenger class.
54
55 A RUN is a set of events.
56
57 4- VISUALIZATION
58
59 The Visualization Manager is set in the main() (see TestEm6.cc).
60 The initialisation of the drawing is done via the command
61 > /control/execute vis.mac
62
63 The detector has a default view which is a longitudinal view of the box.
64
65 The tracks are drawn at the end of event, and erased at the end of run.
66 Optionally one can choose to draw all particles, only the charged ones,
67 or none. This command is defined in EventActionMessenger class.
68
69 5- PHYSICS DEMO
70
71 The particle's type and the physics processes which will be available
72 in this example are set in PhysicsList class.
73
74 In addition a build-in interactive command (/process/inactivate procname)
75 allows to activate/inactivate the processes one by one.
76
77 The threshold for producing secondaries can be changed.
78 eg: /run/particle/setCut 100 micrometer
79 /run/initialize
80
81 To visualize the GammaConversionToMuons :
82 /control/execute run01.mac
83 /control/execute vis.mac
84 /run/beamOn
85
86 To visualize the AnnihiToMuPair :
87 /control/execute run11.mac
88 /control/execute vis.mac
89 /run/beamOn
90
91 Other macros:
92 - run02.mac: the final state of the GammaConversionToMuons
93 - run12.mac: test on carbon target with biasing of cross section
94
95 6- HOW TO START ?
96
97 - execute Test in 'batch' mode from macro files
98 % TestEm6 run01.mac
99
100 - execute Test in 'interactive mode' with visualization
101 % TestEm6
102 ....
103 Idle> type your commands
104 ....
105 Idle> exit
106
107 7- HOW TO INCREASE STATISTICS ON gamma -> mu+mu- ?
108
109 The processes of gamma -> mu+mu- and e+e- -> mu+mu-
110 have a low cross section but can be important
111 for leakage through thick absorbers and calorimeters.
112 Straight forward simulation will be quite time consuming.
113 To make the processes more visible, the cross section can be
114 artificially increased by some factor (here 1000)
115 using the commands (only effective after /run/initialize)
116
117 /testem/phys/SetGammaToMuPairFac 1000
118 /testem/phys/SetAnnihiToMuPairFac 1000
119
120
121 8- HISTOGRAMS
122
123 Testem6 produces 6 histograms, h1 - h6, which illustrate
124 the final state of the GammaConversionToMuons. The histograms are produced
125 with run02.mac and can be displayed with the ROOT macro plotHisto.C.
126
127 The remaining histograms h7 - h16 show various cross sections and h17 the ratio
128 of eeToHadr/eeToMu, see their definitions in RunAction.cc
129
130 By default the histograms are saved as testem6.root
131
132 The format of the histogram file can be : root (default), xml, csv,
133 by selecting the analysis manager default file type in RunAction.cc
