| Geant4 Cross Reference |
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2 2
3 ========================================= 3 =========================================================
4 Geant4 - an Object-Oriented Toolkit for S 4 Geant4 - an Object-Oriented Toolkit for Simulation in HEP
5 ========================================= 5 =========================================================
6 6
7 TestPolarization 7 TestPolarization
8 ---------------- 8 ----------------
9 9
10 How to compute and plot the QED processes in 10 How to compute and plot the QED processes including
11 polarization. 11 polarization.
12 Two possible scenarios are available: 12 Two possible scenarios are available:
13 - Polarization transfer of an incoming beam 13 - Polarization transfer of an incoming beam to final state particles
14 - Material dependent transmission of a polar 14 - Material dependent transmission of a polarized beams.
15 The method is explained below : see item Phy 15 The method is explained below : see item Physics.
16 16
17 1- GEOMETRY DEFINITION 17 1- GEOMETRY DEFINITION
18 18
19 The geometry consists of a single block of a 19 The geometry consists of a single block of a homogeneous material,
20 placed in a world. 20 placed in a world.
21 21
22 Three parameters define the geometry : 22 Three parameters define the geometry :
23 - the material of the box, 23 - the material of the box,
24 - the thickness of the box (sizeZ), 24 - the thickness of the box (sizeZ),
25 - the transverse dimension of the box (size 25 - the transverse dimension of the box (sizeXY).
26 26
27 The default geometry (5mm of Iron, G4_ 27 The default geometry (5mm of Iron, G4_Fe) is constructed in
28 DetectorConstruction, but the above paramete 28 DetectorConstruction, but the above parameters can be changed
29 interactively via the commands defined in De 29 interactively via the commands defined in DetectorMessenger.
30 Its polarization can be accessed via t 30 Its polarization can be accessed via the PolarizationMessenger
31 (see example macro file), and is given 31 (see example macro file), and is given in the global coordinate
32 system. 32 system.
33 33
34 2- PHYSICS LIST 34 2- PHYSICS LIST
35 35
36 The Physics List contains QED particle defin 36 The Physics List contains QED particle definitions (electrons,
37 positrons and photons) and a general t 37 positrons and photons) and a general transportation process.
38 In addition the user can add one of th 38 In addition the user can add one of the two process modules:
39 1. "standard" - standard (unpolarized) EM 39 1. "standard" - standard (unpolarized) EM physics
40 2. "polarized" - polarized EM physics 40 2. "polarized" - polarized EM physics
41 These physics list contain the standard elec 41 These physics list contain the standard electromagnetic processes.
42 42
43 3- AN EVENT : THE PRIMARY GENERATOR 43 3- AN EVENT : THE PRIMARY GENERATOR
44 44
45 The primary kinematic consists of a single p 45 The primary kinematic consists of a single particle starting
46 at the edge of the box. The type of th 46 at the edge of the box. The type of the particle and its
47 energy are set in PrimaryGeneratorActi 47 energy are set in PrimaryGeneratorAction (10 MeV electron).
48 By default the ParticleGun polarizatio 48 By default the ParticleGun polarization is zero.
49 All parameter can be changed via the G 49 All parameter can be changed via the G4 build-in commands of
50 ParticleGun class (see the macros prov 50 ParticleGun class (see the macros provided with this example).
51 51
52 4- PHYSICS 52 4- PHYSICS
53 53
54 This example uses the following physics p 54 This example uses the following physics processes:
55 55
56 - electromagnetic: 56 - electromagnetic:
57 photo-electric effect 57 photo-electric effect
58 Compton scattering 58 Compton scattering
59 pair production 59 pair production
60 bremsstrahlung 60 bremsstrahlung
61 ionization 61 ionization
62 multiple scattering 62 multiple scattering
63 annihilation 63 annihilation
64 or 64 or
65 - polarized electromagnetic: 65 - polarized electromagnetic:
66 (incl. simulation of polarization tra 66 (incl. simulation of polarization transfer, and
67 asymmetries for longitudinally polar 67 asymmetries for longitudinally polarized leptons, and
68 circularly polarized photons) 68 circularly polarized photons)
69 69
70 polarized photo-electric effect 70 polarized photo-electric effect
71 polarized Compton scattering 71 polarized Compton scattering
72 polarized pair production 72 polarized pair production
73 polarized bremsstrahlung 73 polarized bremsstrahlung
74 polarized ionization 74 polarized ionization
75 multiple scattering 75 multiple scattering
76 polarized annihilation 76 polarized annihilation
77 and 77 and
78 - transportation 78 - transportation
79 79
80 and defines the following particles: 80 and defines the following particles:
81 electron, positron, photon 81 electron, positron, photon
82 82
83 83
84 5- HISTOGRAMS 84 5- HISTOGRAMS
85 85
86 The test contains 12 built-in 1D histograms, 86 The test contains 12 built-in 1D histograms, which are managed by the
87 HistoManager class and its Messenger. The hi 87 HistoManager class and its Messenger. The histos can be individually
88 activated with the command : 88 activated with the command :
89 /analysis/h1/set id nbBins valMin val 89 /analysis/h1/set id nbBins valMin valMax unit
90 where unit is the desired unit for the histo 90 where unit is the desired unit for the histo (MeV or keV, etc..)
91 (see the macro histos.mac). 91 (see the macro histos.mac).
92 92
93 1 gamma energy 93 1 gamma energy
94 2 gamma cos(theta) 94 2 gamma cos(theta)
95 3 gamma phi 95 3 gamma phi
96 4 gamma polarization 96 4 gamma polarization
97 5 electron energy 97 5 electron energy
98 6 electron cos(theta) 98 6 electron cos(theta)
99 7 electron phi 99 7 electron phi
100 8 electron polarization 100 8 electron polarization
101 9 positron energy 101 9 positron energy
102 10 positron cos(theta) 102 10 positron cos(theta)
103 11 positron phi 103 11 positron phi
104 12 positron polarization 104 12 positron polarization
105 105
106 6- VISUALIZATION 106 6- VISUALIZATION
107 107
108 Simulated events can be displayed on top 108 Simulated events can be displayed on top of a representation of
109 the geometry, see vis.mac for an example. 109 the geometry, see vis.mac for an example.
110 110
111 7- HOW TO START ? 111 7- HOW TO START ?
112 112
113 compile and link to generate an executable 113 compile and link to generate an executable
114 % gmake 114 % gmake
115 115
116 execute Pol01 in 'batch' mode from the defau 116 execute Pol01 in 'batch' mode from the default macro file :
117 % Pol01 pol01.in 117 % Pol01 pol01.in
118 118
119 or execute Pol01 in 'batch' mode including a << 119 or execute Pol01 in 'batch' mode including aida output :
120 % Pol01 histos.mac 120 % Pol01 histos.mac
121 121
122 if available use JAIDA to display the 122 if available use JAIDA to display the results via
123 % gmake plots 123 % gmake plots
124 124
125 a visualisation example is available by call 125 a visualisation example is available by calling
126 % Pol01 126 % Pol01
127 [...] 127 [...]
128 PreInit> /control/execute vis. 128 PreInit> /control/execute vis.mac