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