| Geant4 Cross Reference |
>> 1 $Id: README,v 1.2 2007-12-04 10:34:17 schaelic Exp $
1 ---------------------------------------------- 2 -------------------------------------------------------------------
2 3
3 ========================================= 4 =========================================================
4 Geant4 - an Object-Oriented Toolkit for S 5 Geant4 - an Object-Oriented Toolkit for Simulation in HEP
5 ========================================= 6 =========================================================
6 7
7 TestPolarization 8 TestPolarization
8 ---------------- 9 ----------------
9 10
10 How to compute and plot the QED processes in 11 How to compute and plot the QED processes including
11 polarization. 12 polarization.
12 Two possible scenarios are available: 13 Two possible scenarios are available:
13 - Polarization transfer of an incoming beam 14 - Polarization transfer of an incoming beam to final state particles
14 - Material dependent transmission of a polar 15 - Material dependent transmission of a polarized beams.
15 The method is explained below : see item Phy 16 The method is explained below : see item Physics.
16 17
17 1- GEOMETRY DEFINITION 18 1- GEOMETRY DEFINITION
18 19
19 The geometry consists of a single block of a 20 The geometry consists of a single block of a homogeneous material,
20 placed in a world. 21 placed in a world.
21 22
22 Three parameters define the geometry : 23 Three parameters define the geometry :
23 - the material of the box, 24 - the material of the box,
24 - the thickness of the box (sizeZ), 25 - the thickness of the box (sizeZ),
25 - the transverse dimension of the box (size 26 - the transverse dimension of the box (sizeXY).
26 27
27 The default geometry (5mm of Iron, G4_ 28 The default geometry (5mm of Iron, G4_Fe) is constructed in
28 DetectorConstruction, but the above paramete 29 DetectorConstruction, but the above parameters can be changed
29 interactively via the commands defined in De 30 interactively via the commands defined in DetectorMessenger.
30 Its polarization can be accessed via t 31 Its polarization can be accessed via the PolarizationMessenger
31 (see example macro file), and is given 32 (see example macro file), and is given in the global coordinate
32 system. 33 system.
33 34
34 2- PHYSICS LIST 35 2- PHYSICS LIST
35 36
36 The Physics List contains QED particle defin 37 The Physics List contains QED particle definitions (electrons,
37 positrons and photons) and a general t 38 positrons and photons) and a general transportation process.
38 In addition the user can add one of th 39 In addition the user can add one of the two process modules:
39 1. "standard" - standard (unpolarized) EM 40 1. "standard" - standard (unpolarized) EM physics
40 2. "polarized" - polarized EM physics 41 2. "polarized" - polarized EM physics
41 These physics list contain the standard elec 42 These physics list contain the standard electromagnetic processes.
42 43
43 3- AN EVENT : THE PRIMARY GENERATOR 44 3- AN EVENT : THE PRIMARY GENERATOR
44 45
45 The primary kinematic consists of a single p 46 The primary kinematic consists of a single particle starting
46 at the edge of the box. The type of th 47 at the edge of the box. The type of the particle and its
47 energy are set in PrimaryGeneratorActi 48 energy are set in PrimaryGeneratorAction (10 MeV electron).
48 By default the ParticleGun polarizatio 49 By default the ParticleGun polarization is zero.
49 All parameter can be changed via the G 50 All parameter can be changed via the G4 build-in commands of
50 ParticleGun class (see the macros prov 51 ParticleGun class (see the macros provided with this example).
51 52
52 4- PHYSICS 53 4- PHYSICS
53 54
54 This example uses the following physics p 55 This example uses the following physics processes:
55 56
56 - electromagnetic: 57 - electromagnetic:
57 photo-electric effect 58 photo-electric effect
58 Compton scattering 59 Compton scattering
59 pair production 60 pair production
60 bremsstrahlung 61 bremsstrahlung
61 ionization 62 ionization
62 multiple scattering 63 multiple scattering
63 annihilation 64 annihilation
64 or 65 or
65 - polarized electromagnetic: 66 - polarized electromagnetic:
66 (incl. simulation of polarization tra 67 (incl. simulation of polarization transfer, and
67 asymmetries for longitudinally polar 68 asymmetries for longitudinally polarized leptons, and
68 circularly polarized photons) 69 circularly polarized photons)
69 70
70 polarized photo-electric effect 71 polarized photo-electric effect
71 polarized Compton scattering 72 polarized Compton scattering
72 polarized pair production 73 polarized pair production
73 polarized bremsstrahlung 74 polarized bremsstrahlung
74 polarized ionization 75 polarized ionization
75 multiple scattering 76 multiple scattering
76 polarized annihilation 77 polarized annihilation
77 and 78 and
78 - transportation 79 - transportation
79 80
80 and defines the following particles: 81 and defines the following particles:
81 electron, positron, photon 82 electron, positron, photon
82 83
83 84
84 5- HISTOGRAMS 85 5- HISTOGRAMS
85 86
86 The test contains 12 built-in 1D histograms, 87 The test contains 12 built-in 1D histograms, which are managed by the
87 HistoManager class and its Messenger. The hi 88 HistoManager class and its Messenger. The histos can be individually
88 activated with the command : 89 activated with the command :
89 /analysis/h1/set id nbBins valMin val << 90 /testem/histo/setHisto id nbBins valMin valMax unit
90 where unit is the desired unit for the histo 91 where unit is the desired unit for the histo (MeV or keV, etc..)
91 (see the macro histos.mac). 92 (see the macro histos.mac).
92 93
93 1 gamma energy 94 1 gamma energy
94 2 gamma cos(theta) 95 2 gamma cos(theta)
95 3 gamma phi 96 3 gamma phi
96 4 gamma polarization 97 4 gamma polarization
97 5 electron energy 98 5 electron energy
98 6 electron cos(theta) 99 6 electron cos(theta)
99 7 electron phi 100 7 electron phi
100 8 electron polarization 101 8 electron polarization
101 9 positron energy 102 9 positron energy
102 10 positron cos(theta) 103 10 positron cos(theta)
103 11 positron phi 104 11 positron phi
104 12 positron polarization 105 12 positron polarization
>> 106
>> 107 If AIDA is available, i.e. if G4ANALYSIS_USE is set, these
>> 108 histograms are stored in a compressed XML file
>> 109 (pol01.aida). These results can be displayed using a small
>> 110 program (plotResults.java) based on JAIDA by simply calling
>> 111
>> 112 % gmake plots
105 113
106 6- VISUALIZATION 114 6- VISUALIZATION
107 115
108 Simulated events can be displayed on top 116 Simulated events can be displayed on top of a representation of
109 the geometry, see vis.mac for an example. 117 the geometry, see vis.mac for an example.
110 118
111 7- HOW TO START ? 119 7- HOW TO START ?
112 120
113 compile and link to generate an executable 121 compile and link to generate an executable
114 % gmake 122 % gmake
115 123
116 execute Pol01 in 'batch' mode from the defau << 124 execute pol01 in 'batch' mode from the default macro file :
117 % Pol01 pol01.in << 125 % pol01 pol01.in
118 126
119 or execute Pol01 in 'batch' mode including a << 127 or execute pol01 in 'batch' mode including aida output :
120 % Pol01 histos.mac << 128 % pol01 histos.mac
121 129
122 if available use JAIDA to display the 130 if available use JAIDA to display the results via
123 % gmake plots 131 % gmake plots
124 132
125 a visualisation example is available by call 133 a visualisation example is available by calling
126 % Pol01 << 134 % pol01
127 [...] 135 [...]
128 PreInit> /control/execute vis. 136 PreInit> /control/execute vis.mac