source: trunk/examples/extended/analysis/A01/README@ 1337

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1$Id: README,v 1.10 2009/11/21 00:22:55 perl Exp $
2
3 =========================================================
4 Geant4 - an Object-Oriented Toolkit for Simulation in HEP
5 =========================================================
6
7 Extended Example A01
8 --------------------
9
10 Example A01 implements a double-arm spectrometer with wire chambers,
11 hodoscopes and calorimeters. Event simulation and collection are
12 enabled, as well as event display and analysis.
13
14
15 1. GEOMETRY
16
17 The spectrometer consists of two detector arms. One arm provides
18 position and timing information of the incident particle while the
19 other collects position, timing and energy information of the particle
20 after it has been deflected by a magnetic field centered at the
21 spectrometer pivot point.
22
23 - First arm: box filled with air, also containing:
24
25 1 hodoscope (15 vertical strips of plastic scintillator)
26 1 drift chamber (5 horizontal argon gas layers with a
27 "virtual wire" at the center of each layer)
28
29 - Magnetic field region: air-filled cylinder which contains
30 the field
31
32 - Second arm: box filled with air, also containing:
33
34 1 hodoscope (25 vertical strips of plastic scintillator)
35 1 drift chamber (5 horizontal argon gas layers with a
36 "virtual wire" at the center of each layer)
37 1 electromagnetic calorimeter:
38 a box sub-divided along x,y and z
39 axes into cells of CsI
40 1 hadronic calorimeter:
41 a box sub-divided along x,y, and z axes
42 into cells of lead, with a layer of
43 plastic scintillator placed at the center
44 of each cell
45
46
47 2. PHYSICS
48
49 This example uses the following physics processes:
50
51 - electromagnetic:
52 photo-electric effect
53 Compton scattering
54 pair production
55 bremsstrahlung
56 ionization
57 multiple scattering
58 annihilation
59
60 - decay
61
62 - transportation in a field
63
64 and defines the following particles:
65 geantino, charged geantino, gamma, all leptons,
66 pions, charged kaons
67
68 Note that even though hadrons are defined, no hadronic processes
69 are invoked in this example.
70
71
72 3. EVENT:
73
74 An event consists of the generation of a single particle which is
75 transported through the first spectrometer arm. Here, a scintillator
76 hodoscope records the reference time of the particle before it passes
77 through a drift chamber where the particle position is measured.
78 Momentum analysis is performed as the particle passes through a magnetic
79 field at the spectrometer pivot and then into the second spectrometer
80 arm. In the second arm, the particle passes through another hodoscope
81 and drift chamber before interacting in the electromagnetic calorimeter.
82 Here it is likely that particles will induce electromagnetic showers.
83 The shower energy is recorded in a three-dimensional array of CsI
84 crystals. Secondary particles from the shower, as well as primary
85 particles which do not interact in the CsI crystals, pass into the
86 hadronic calorimeter. Here, the remaining energy is collected in a
87 three-dimensional array of scintillator-lead sandwiches.
88
89 Several aspects of the event may be changed interactively by the user:
90
91 - initial particle type
92 - initial momentum and angle
93 - momentum and angle spreads
94 - type of initial particle may be randomized
95 - strength of magnetic field
96 - angle of the second spectrometer arm
97
98
99 4. DETECTOR RESPONSE:
100
101 All the information required to simulate and analyze an event is
102 recorded in HITS. This information is recorded in the following
103 sensitive detectors:
104
105 - hodoscope:
106 particle time
107 particle position
108 strip ID
109
110 - drift chamber:
111 particle time
112 particle position
113 layer ID
114
115 - electromagnetic calorimeter:
116 particle position
117 energy deposited in cell
118 cell ID
119
120 - hadronic calorimeter:
121 particle position
122 energy deposited in cell
123 cell ID
124
125
126 5. VISUALIZATION:
127
128 Simulated events can be displayed on top of a representation of the spectrometer.
129
130 vis.mac outputs HepRep version 1 files suitable for viewing in HepRApp or WIRED4.
131 Change the /vis/open line from HepRepFile to DAWNFILE to instead
132 make .prim files suitable for viewing in DAWN.
133
134 heprep2-000-gz.mac outputs a series of gzipped HepRep version 2 files
135 each containing a single event, suitable for viewing in HepRApp or WIRED4
136
137 heprep2zip.mac outputs a single zip file that unzips to a series of
138 HepRep version 2 files, each each containing a single event (unzip
139 the single file by hand, then view the resulting individial HepRep files).
140
141 heprep2-000-zip.mac outputs a series of zipped HepRep version 2 files
142 each containing a single event (not yet viewable unless you
143 explicitly unzip them before viewing).
144
145 heprep2.mac outputs a HepRep version 2 file with multiple events
146 appended to a single file in an experimental manner
147
148 heprep2gz.mac outputs a HepRep version 2 file with multiple events
149 appended to a single file in an experimental manner
150
151 Any of the heprep mac files above with the name bheprep (for instance
152 bheprep2zip.mac) will write a Binary HepRep version 2 file, readable only
153 by WIRED4 (not by HepRApp).
154
155
156 6. ANALYSIS:
157
158 This example implements an AIDA-compliant analysis system which
159 creates histograms, ntuples and plotters. If you have built Geant4 with
160 the option to use anlaysis (answering yes to the appropriate question in
161 ./Configure -build), then at the completion of a simulation run,
162 a file A01.aida is produced which contains these data structures.
163 This file can be used as an input to the Java Analysis Studio (JAS) which allows
164 the histograms and ntuples to examined, manipulated, saved and printed.
165 For further details, see README.JAIDA.
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