Gabriele Cosmo
129 lines
5.3 KiB
Plaintext
129 lines
5.3 KiB
Plaintext
-------------------------------------------------------------------
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=========================================================
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Geant4 - an Object-Oriented Toolkit for Simulation in HEP
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=========================================================
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TestEm15
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--------
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How to compute and plot the final state of Multiple Scattering
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or Gamma Conversion considered as an isolated processes.
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The method is exposed below : see item Physics.
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1- GEOMETRY DEFINITION
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It is a single box representing a 'semi infinite' homogeneous medium.
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Two parameters define the geometry :
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- the material of the box,
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- the (full) size of the box.
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The default geometry (100 m of water) is constructed in
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DetectorConstruction, but the above parameters can be changed
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interactively via the commands defined in DetectorMessenger.
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2- PHYSICS LIST
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The physics list contains the standard electromagnetic processes.
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In order not to introduce 'artificial' constraints on the step size,
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there is no limitation from the maximum energy lost per step.
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3- AN EVENT : THE PRIMARY GENERATOR
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The primary kinematic consists of a single particle starting at the edge
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of the box. The type of the particle and its energy are set in
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PrimaryGeneratorAction (1 MeV electron), and can be changed via the G4
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build-in commands of ParticleGun class (see the macros provided with
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this example).
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4- PHYSICS
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All discrete processes are inactivated (see provided macros),
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so that Multiple Scattering or Gamma Conversion is 'forced' to
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determine the first step of the primary particle.
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The step size and the final state are computed and plotted.
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Then the event is immediately killed.
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The result is compared with the 'input' data, i.e. with the cross
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sections stored in the PhysicsTables and used by Geant4.
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The stepMax command provides an additional control of the step size of
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the multiple scattering.
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5- HISTOGRAMS
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The test contains 16 built-in 1D histograms, which are managed by
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G4AnalysisManager and its Messenger. The histos can be individually
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activated with the command :
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/analysis/h1/set id nbBins valMin valMax unit
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where unit is the desired unit for the histo (MeV or keV, etc..)
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(see the macros xxxx.mac).
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1 Multiple Scattering. True step length
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2 Multiple Scattering. Geom step length
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3 Multiple Scattering. Ratio geomSl/trueSl
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4 Multiple Scattering. Lateral displacement: radius
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5 Multiple Scattering. Lateral displac: psi_space
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6 Multiple Scattering. Angular distrib: theta_plane
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7 Multiple Scattering. Phi-position angle
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8 Multiple Scattering. Phi-direction angle
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9 Multiple Scattering. Correlation: cos(phiPos-phiDir)
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10 Gamma Conversion. Open Angle * Egamma
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11 Gamma Conversion. Log10(P recoil)
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12 Gamma Conversion. Phi P recoil angle
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13 Gamma Conversion. Phi P plus angle
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14 Gamma Conversion. 2 * cos(phiplus + phiminus) Asymmetry
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15 Gamma Conversion. E plus / E gamma
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16 Gamma Conversion. Phi of Gamma Polarization
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The histograms are managed by the HistoManager class and its Messenger.
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The histos can be individually activated with the command :
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/analysis/h1/set id nbBins valMin valMax unit
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where unit is the desired unit for the histo (MeV or keV, deg or mrad, etc..)
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One can control the name of the histograms file with the command:
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/analysis/setFileName name (default testem15)
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It is possible to choose the format of the histogram file : root (default),
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hbook, xml, csv, by using namespace in HistoManager.hh
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It is also possible to print selected histograms on an ascii file:
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/analysis/h1/setAscii id
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All selected histos will be written on a file name.ascii (default testem15)
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6- VISUALIZATION
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The Visualization Manager is set in the main().
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The initialization of the drawing is done via the commands
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/vis/... in the macro vis.mac. To get visualization:
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> /control/execute vis.mac
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The detector has a default view which is a longitudinal view of the
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box.
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The tracks are drawn at the end of event, and erased at the end of run.
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7- HOW TO START ?
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execute TestEm15 in 'batch' mode from macro files :
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% TestEm15 compt.mac
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execute TestEm15 in 'interactive mode' with visualization :
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% TestEm15
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Idle> control/execute vis.mac
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....
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Idle> type your commands
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....
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Idle> exit
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8 - MACROS
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The examples of macros for Multiple Scattering:
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electron.mac muon.mac proton.mac
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The example of Gamma Conversion macro :
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gamma.mac - gamma to e+ e-
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gamma2mumu.mac gamma to mu+ mu-
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