[807] | 1 | $Id: README,v 1.15 2005/11/22 16:58:54 maire 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 | TestEm6 |
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| 9 | ------- |
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| 10 | This example is intended to test the processes of gamma conversion |
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| 11 | to a pair of muons and annihilation of positrons with atomic |
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| 12 | electrons to a pair of muons. |
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| 13 | To make these process more visible, the usually much more frequent |
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| 14 | gamma conversion to a pair of electrons and the standard positron |
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| 15 | processes are not selected in the physics list. |
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| 16 | |
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| 17 | 1- GEOMETRY DEFINITION |
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| 18 | |
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| 19 | The geometry consists of a single block of a homogenous material. |
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| 20 | |
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| 21 | Two parameters define the geometry : |
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| 22 | - the material of the box, |
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| 23 | - the (full) size of the box. |
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| 24 | The default is 500 m of iron. |
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| 25 | |
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| 26 | In addition a transverse uniform magnetic field can be applied. |
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| 27 | |
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| 28 | The default geometry is constructed in DetectorConstruction class, |
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| 29 | but all of the above parameters can be changed interactively via |
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| 30 | the commands defined in the DetectorMessenger class. |
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| 31 | |
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| 32 | 2- PHYSICS LIST |
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| 33 | |
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| 34 | The particle list is the one of novice/exampleN03. |
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| 35 | The physics list contains the 'standard' electromagnetic processes, |
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| 36 | and decay. |
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| 37 | |
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| 38 | For Gamma, only the GammaConversionToMuons has been registered. |
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| 39 | Futhermore, a high production cut (1 km, which gives infinity in energy) |
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| 40 | prevent any production of delta-electrons from ionization or gamma |
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| 41 | from bremsstrahlung. |
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| 42 | For Positrons, only the annihilation process is selected. |
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| 43 | |
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| 44 | |
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| 45 | 3- AN EVENT : THE PRIMARY GENERATOR |
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| 46 | |
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| 47 | The primary kinematic consists of a single particle which hits the |
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| 48 | block perpendicular to the input face. The type of the particle |
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| 49 | and its energy are set in the PrimaryGeneratorAction class, and can |
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| 50 | changed via the G4 build-in commands of ParticleGun class (see |
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| 51 | the macros provided with this example). |
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| 52 | The default is a Gamma of 100 TeV. |
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| 53 | |
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| 54 | In addition one can choose randomly the impact point of the incident |
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| 55 | particle. The corresponding interactive command is built in |
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| 56 | PrimaryGeneratorMessenger class. |
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| 57 | |
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| 58 | A RUN is a set of events. |
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| 59 | |
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| 60 | |
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| 61 | 4- VISUALIZATION |
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| 62 | |
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| 63 | The Visualization Manager is set in the main(). |
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| 64 | The initialisation of the drawing is done via the command |
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| 65 | > /control/execute vis.mac |
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| 66 | |
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| 67 | The detector has a default view which is a longitudinal view of the box. |
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| 68 | |
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| 69 | The tracks are drawn at the end of event, and erased at the end of run. |
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| 70 | Optionaly one can choose to draw all particles, only the charged one, |
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| 71 | or none. This command is defined in EventActionMessenger class. |
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| 72 | |
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| 73 | 5- PHYSICS DEMO |
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| 74 | |
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| 75 | The particle's type and the physic processes which will be available |
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| 76 | in this example are set in PhysicsList class. |
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| 77 | |
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| 78 | In addition a build-in interactive command (/process/inactivate proname) |
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| 79 | allows to activate/inactivate the processes one by one. |
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| 80 | |
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| 81 | The threshold for producing secondaries can be changed. |
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| 82 | eg: /run/particle/setCut 100 micrometer |
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| 83 | /run/initialize |
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| 84 | |
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| 85 | To visualize the GammaConversionToMuons : |
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| 86 | /control/execute run01.mac |
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| 87 | /control/execute vis.mac |
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| 88 | /run/beamOn |
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| 89 | |
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| 90 | To visualize the AnnihiToMuPair : |
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| 91 | /control/execute run11.mac |
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| 92 | /control/execute vis.mac |
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| 93 | /run/beamOn |
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| 94 | |
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| 95 | 6- HOW TO START ? |
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| 96 | |
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| 97 | - compile and link to generate an executable |
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| 98 | % cd geant4/examples/extended/electromagnetic/TestEm6 |
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| 99 | % gmake |
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| 100 | |
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| 101 | - execute Test in 'batch' mode from macro files |
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| 102 | % TestEm6 run01.mac |
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| 103 | |
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| 104 | - execute Test in 'interactive mode' with visualization |
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| 105 | % TestEm6 |
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| 106 | .... |
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| 107 | Idle> type your commands |
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| 108 | .... |
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| 109 | Idle> exit |
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| 110 | |
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| 111 | 7- HOW TO INCREASE STATISTICS ON gamma -> mu+mu- ? |
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| 112 | |
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| 113 | The processes of gamma -> mu+mu- and e+e- -> mu+mu- |
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| 114 | have a low cross section but can be important |
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| 115 | for leakage through thick absorbers and calorimeters. |
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| 116 | Straight forward simulation will be quite time consuming. |
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| 117 | To make the processes more visible, the cross section can be |
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| 118 | artificially increased by some factor (here 1000) |
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| 119 | using the commands (only effective after /run/initialize) |
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| 120 | |
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| 121 | /testem/phys/SetGammaToMuPairFac 1000 |
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| 122 | /testem/phys/SetAnnihiToMuPairFac 1000 |
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| 123 | |
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| 124 | |
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| 125 | 8- HISTOGRAMS |
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| 126 | |
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| 127 | Testem6 produces 6 histograms which illustrate the final state of |
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| 128 | the GammaConversionToMuons process. See their definitions in RunAction.cc |
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| 129 | |
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| 130 | By default the histograms are not activated. To activate histograms |
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| 131 | the environment variable G4ANALYSIS_USE should be defined. For instance |
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| 132 | uncomment the flag G4ANALYSIS_USE in GNUmakefile. |
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| 133 | |
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| 134 | Before compilation of the example it is optimal to clean up old files: |
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| 135 | gmake histclean |
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| 136 | gmake |
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| 137 | |
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| 138 | By default the histograms are saved as testem6.hbook |
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| 139 | It is possible to choose the format of the histogram file (hbook, root, XML): |
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| 140 | comment/uncomment 1 line in the constructor of RunAction. |
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| 141 | |
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| 142 | To use histograms, at least one of the AIDA implementations should be |
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| 143 | available (see http://aida.freehep.org). |
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| 144 | |
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| 145 | 8a - PI |
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| 146 | |
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| 147 | A package including AIDA and extended interfaces also using Python is PI, |
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| 148 | available from: http://cern.ch/pi |
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| 149 | |
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| 150 | Once installed PI or PI-Lite in a specified local area $MYPY, it is required |
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| 151 | to add the installation path to $PATH, i.e. for example, for release 1.2.1 of |
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| 152 | PI: |
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| 153 | setenv PATH ${PATH}:$MYPI/1.2.1/app/releases/PI/PI_1_2_1/rh73_gcc32/bin |
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| 154 | |
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| 155 | CERN users can use the PATH to the LCG area on AFS. |
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| 156 | Before running the example the command should be issued: |
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| 157 | eval `aida-config --runtime csh` |
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| 158 | |
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| 159 | 8b - OpenScientist |
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| 160 | |
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| 161 | OpenScientist is available at http://OpenScientist.lal.in2p3.fr. |
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| 162 | |
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| 163 | You have to "setup" the OpenScientist AIDA implementation before compiling |
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| 164 | (then with G4ANALYSIS_USE set) and running your Geant4 application. |
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| 165 | |
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| 166 | On UNIX you setup, with a csh flavoured shell : |
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| 167 | csh> source <<OpenScientist install path>/aida-setup.csh |
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| 168 | or with a sh flavoured shell : |
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| 169 | sh> . <<OpenScientist install path>/aida-setup.sh |
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| 170 | On Windows : |
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| 171 | DOS> call <<OpenScientist install path>/aida-setup.bat |
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| 172 | |
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| 173 | You can use various file formats for writing (AIDA-XML, hbook, root). |
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| 174 | These formats are readable by the Lab onx interactive program |
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| 175 | or the OpenPAW application. See the web pages. |
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| 176 | |
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| 177 | |
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| 178 | With OpenPAW, on a run.hbook file, one can view the histograms |
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| 179 | with something like : |
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| 180 | OS> opaw |
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| 181 | opaw> h/file 1 run.hbook ( or opaw> h/file 1 run.aida or run.root) |
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| 182 | opaw> zone 2 2 |
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| 183 | opaw> h/plot 1 |
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| 184 | opaw> h/plot 2 |
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