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Geant4/examples/extended/electromagnetic/TestEm6/README

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  1 -------------------------------------------------------------------
  2 
  3      =========================================================
  4      Geant4 - an Object-Oriented Toolkit for Simulation in HEP
  5      =========================================================
  6 
  7                             TestEm6 
  8                             -------
  9      This example is intended to test the processes of gamma conversion
 10      to a pair of muons and annihilation of positrons with atomic
 11      electrons to a pair of muons.
 12   
 13  1- GEOMETRY DEFINITION
 14  
 15      The geometry consists of a single block of a homogenous material.
 16       
 17      Two parameters define the geometry :
 18       - the material of the box,
 19       - the (full) size of the box.
 20      The default is 500 m of iron.
 21         
 22      In addition a transverse uniform magnetic field can be applied.
 23   
 24      The default geometry is constructed in DetectorConstruction class,
 25      but all of the above parameters can be changed interactively via
 26      the commands defined in the DetectorMessenger class.
 27   
 28  2- PHYSICS LIST
 29 
 30      Physics Lists are based on modular design. Several modules are 
 31      instantiated:
 32      1. Transportation
 33      2. EM physics
 34      3. Decays
 35      4. StepMax - for step limitation
 36   
 37      The electromagnetic physics is chosen from one of the Geant4 EM
 38      physics constructors in the physics_list library.
 39 
 40      Cross sections can be enhanced (see below).
 41    
 42  3- AN EVENT : THE PRIMARY GENERATOR
 43  
 44      The primary kinematic consists of a single particle which hits the
 45      block perpendicular to the input face. The type of the particle
 46      and its energy are set in the PrimaryGeneratorAction class, and can
 47      changed via the G4 build-in commands of G4ParticleGun class (see
 48      the macros provided with this example).
 49      The default is a Gamma of 100 TeV.
 50       
 51      In addition one can choose randomly the impact point of the incident
 52      particle. The corresponding interactive command is built in
 53      PrimaryGeneratorMessenger class.
 54     
 55      A RUN is a set of events.
 56         
 57  4- VISUALIZATION
 58  
 59      The Visualization Manager is set in the main() (see TestEm6.cc).
 60      The initialisation of the drawing is done via the command
 61      > /control/execute vis.mac
 62   
 63      The detector has a default view which is a longitudinal view of the box.
 64   
 65      The tracks are drawn at the end of event, and erased at the end of run.
 66      Optionally one can choose to draw all particles, only the charged ones,
 67      or none. This command is defined in EventActionMessenger class.
 68 
 69  5- PHYSICS DEMO
 70 
 71      The particle's type and the physics processes which will be available
 72      in this example are set in PhysicsList class.
 73 
 74      In addition a build-in interactive command (/process/inactivate procname)
 75      allows to activate/inactivate the processes one by one.
 76 
 77      The threshold for producing secondaries can be changed.
 78      eg: /run/particle/setCut 100 micrometer
 79          /run/initialize
 80 
 81      To visualize the GammaConversionToMuons :
 82         /control/execute run01.mac
 83         /control/execute vis.mac
 84         /run/beamOn
 85 
 86      To visualize the AnnihiToMuPair :
 87         /control/execute run11.mac
 88         /control/execute vis.mac
 89         /run/beamOn
 90 
 91      Other macros:
 92      - run02.mac: the final state of the GammaConversionToMuons
 93      - run12.mac: test on carbon target with biasing of cross section
 94 
 95  6- HOW TO START ?
 96  
 97      - execute Test  in 'batch' mode from macro files
 98   % TestEm6    run01.mac
 99     
100      - execute Test  in 'interactive mode' with visualization
101   % TestEm6 
102     ....
103   Idle> type your commands
104     ....
105   Idle> exit
106  
107  7- HOW TO INCREASE STATISTICS ON gamma -> mu+mu- ?
108  
109      The processes of gamma -> mu+mu-  and e+e- -> mu+mu-
110      have a low cross section but can be important
111      for leakage through thick absorbers and calorimeters.
112      Straight forward simulation will be quite time consuming.
113      To make the processes more visible, the cross section can be
114      artificially increased by some factor (here 1000)
115      using the commands  (only effective after  /run/initialize)
116 
117      /testem/phys/SetGammaToMuPairFac  1000
118      /testem/phys/SetAnnihiToMuPairFac 1000
119  
120   
121  8- HISTOGRAMS
122  
123   Testem6 produces 6 histograms, h1 - h6, which illustrate
124   the final state of the GammaConversionToMuons. The histograms are produced
125   with run02.mac and can be displayed with the ROOT macro plotHisto.C.
126 
127   The remaining histograms h7 - h16 show various cross sections and h17 the ratio
128   of eeToHadr/eeToMu, see their definitions in RunAction.cc
129   
130   By default the histograms are saved as testem6.root
131 
132   The format of the histogram file can be : root (default), xml, csv,
133   by selecting the analysis manager default file type in RunAction.cc