| Geant4 Cross Reference |
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2
3 =========================================
4 Geant4 - an Object-Oriented Toolkit for S
5 =========================================
6
7 Example HGCal_testbeam
8 ----------------------
9
10 This example is based on the Geant4 standalon
11 by Thorben Quast for the CMS HGCal studies:
12 https://github.com/ThorbenQuast/HGCal_TB_Gean
13
14 The goal of this example is to demonstrate a
15 in HEP experiments, and as a base for the val
16 comparison with experiment data.
17
18 It presents a test beam setup used in the HGC
19 2018. It can be easily extended to other conf
20
21 Details on the High Granularity Calorimeter (
22 i.a. in the Technical Design Report:
23 https://cds.cern.ch/record/2293646/files/CMS-
24
25 1. Detector description
26 -----------------------
27
28 Detector construction in this example assumes
29 constructed with different elements placed on
30 z axis (beam axis).
31 There are 3 configurations user can choose fr
32 with UI command:
33
34 /HGCalTestbeam/setup/configuration <ID>
35
36 where <ID> by default is equal to 0, which me
37 setup used in October 2018.
38 <ID> 1 builds the same calorimeter setup, but
39 several beamline elements.
40 <ID> 2 builds a very simplistic test configur
41
42 Whenever a silicon wafer or SiPM is placed in
43 volume is attached to it, and will be used to
44
45 Silicon wafer is divided into cells (pixels),
46 can collect signal.
47
48 In order to change the maximum step size allo
49
50 /HGCalTestbeam/setup/stepSilicon <STEP>
51
52 where <STEP> is value of the max step size in
53 <STEP> is equal to 30 um.
54
55 2. Signal
56 ---------
57
58 Energy deposited within silicon pixels and Si
59 sensitive detectors. Each deposit is added in
60 of hits, in order to allow the digitisation.
61
62 Digitisation is performed at the end of the e
63 energy deposits within pixels, taking into ac
64 arrival of signal (global time of energy depo
65 cut is applied which means all the deposits a
66 using UI command:
67
68 /HGCalTestbeam/hits/timeCut <TIME>
69
70 where <TIME> is the maximum global time of th
71 would be counted into the signal within the p
72
73 Another hit parameter is TOA (time of arrival
74 as time of the energy deposit which added to
75 exceeds the threshold. By default the thresho
76 means that any hit will exceed the value, so
77 the time of the first energy deposit. It can
78
79 /HGCalTestbeam/hits/toaThreshold <ENERGY_THRE
80
81 where <ENERGY_THRESHOLD> indicates the thresh
82 needs to exceed to be counted as time of arri
83
84 Additionally, for silicon pixels, time of the
85 (within the time window) is recorded.
86
87 3. Output
88 ---------
89
90 Output with event signal is stored in ntuple
91 Its name can be set with UI command:
92
93 /HGCalTestbeam/output/file <NAME>
94
95 Created TTree "hits" contains following branc
96
97 +---------------------------------+-----------
98 | Branch | Type
99 +---------------------------------+-----------
100 | event | int
101 | pdgID | vector<int
102 | beamEnergy | vector<dou
103 | beamX_cm | vector<dou
104 | beamY_cm | vector<dou
105 | beamZ_cm | vector<dou
106 | siliconHits_ID | vector<int
107 | siliconHits_x_cm | vector<dou
108 | siliconHits_y_cm | vector<dou
109 | siliconHits_z_cm | vector<dou
110 | siliconHits_Edep_keV | vector<dou
111 | siliconHits_EdepNonIonizing_keV | vector<dou
112 | siliconHits_TOA_ns | vector<dou
113 | siliconHits_TOA_last_ns | vector<dou
114 | siliconHits_type | vector<int
115 | SiPMHits_ID | vector<int
116 | SiPMHits_x_cm | vector<dou
117 | SiPMHits_y_cm | vector<dou
118 | SiPMHits_z_cm | vector<dou
119 | SiPMHits_Edep_keV | vector<dou
120 | SiPMHits_EdepNonIonizing_keV | vector<dou
121 | SiPMHits_TOA_ns | vector<dou
122 | SiPMHits_type | vector<int
123 | signalSum_HGCAL_GeV | double
124 | COGZ_HGCAL_cm | double
125 | NHits_HGCAL | int
126 | signalSum_AHCAL_GeV | double
127 | COGZ_AHCAL_cm | double
128 | NHits_AHCAL | int
129 +---------------------------------+-----------
130
131 4. Primary particle generator
132 -----------------------------
133
134 Particle gun is used as a default primary par
135 It can be controlled with standard UI command
136 additional ones introduced by the messenger:
137
138 /HGCalTestbeam/generator/momentumSpread <VALU
139 to change constant particle energy to Gaussia
140 sigma expressed in units of the initial energ
141 means sigma of 0.05 * E). By default it equal
142 energy value is used.
143
144 /HGCalTestbeam/generator/beamSpread <none/Gau
145 to define type of beam position spread. By de
146
147 /HGCalTestbeam/generator/beamSpreadX <SIZE>
148 to define size of beam spread along x axis. I
149 Gaussian distribution, or half-width of a fla
150
151 /HGCalTestbeam/generator/beamSpreadY <SIZE>
152 to define size of beam spread along y axis. I
153 Gaussian distribution, or half-width of a fla
154
155 /HGCalTestbeam/generator/fBeamZ0 <POSITION>
156 to define beam position along z axis. By defa
157 world volume is used.
158
159 Additionally, if installation was done with R
160 was able to locate it), an option of input re
161 is enabled. It can be activated with
162
163 /HGCalTestbeam/generator/fReadInputFile true
164
165 /HGCalTestbeam/generator/fPathInputFile <FILE
166 sets the path to the input file.
167
168 /HGCalTestbeam/generator/startFromEvent <N>
169 allows to start simulation from Nth event.
170
171 Please note that in current implementation in
172 executed in a non-multithreaded mode (or with
173
174 Input file needs to have following structure:
175 - TDirectory "VirtualDetector"
176 - TNtuple "HGCAL" with branches:
177 +---------+-------+------+---------------
178 | Branch | Type | Unit | Descr
179 +---------+-------+------+---------------
180 | EventID | float | - | ID of event
181 | PDGid | float | - | Particle type
182 | x | float | mm | Initial X posi
183 | y | float | mm | Initial Y posi
184 | Px | float | MeV | Initial moment
185 | Py | float | MeV | Initial moment
186 | Pz | float | MeV | Initial moment
187 +---------+-------+------+---------------
188
189 Several particles may belong to the same even
190 of them are read from the input file.
191 Z position is set to Z position of the entran
192
193 5. How to run the example
194 -------------------------
195
196 Example can be run in interactive mode, with
197
198 ./HGCal_testbeam
199
200 It will execute init_vis.mac and vis.mac.
201
202 To run in a batch mode, specify the path to t
203
204 ./HGCal_testbeam run.mac
205
206 which will run 10 single-electron events, wit
207 The beam position is smeared with Gaussian wi
208 The momentum is smeared with Gaussian with si
209 Z beam position is set to -1 m.
210 Maximum step size in Si pixel is 20 um.
211 The name of the created file is output_eM_sme
212
213 6. Additional settings
214 ----------------------
215
216 6.1. Particle input from ROOT file
217 ----------------------------------
218
219 If ROOT is found by CMake, it allows to use R
220 the primary generator. See more in the descri
221 particle generator".
222
223 ./HGCal_testbeam readFromFile.mac
224
225 Macro readFromFile.mac can be used but name
226 be specified (not provided with the example)
227 be used in the validation with experimental