Gabriele Cosmo
239 lines
7.3 KiB
Markdown
239 lines
7.3 KiB
Markdown
\page ExampleTestEm15 Example TestEm15
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How to compute and plot the final state of:
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- Multiple Scattering
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- Gamma Conversion
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considered as an isolated processes, see PHYSICS.
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For Multiple Scattering, the method is exposed below.
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For Gamma Conversion, when G4BetheHeitler5DModel Model is used,
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see \ref ExampleTestEm15_GC for Histograms and UI commands description.
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## 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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## PHYSICS LIST
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The physics list contains the standard electromagnetic processes.
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In order not to introduce 'articicial' constraints on the step size,
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there is no limitation from the maximum energy lost per step.
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## 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 G4ParticleGun class (see the macros provided with
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this example).
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## 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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__Multiple Scattering:__
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The result is compared with the 'input' data, i.e. with the cross sections stored in the PhysicsTables and used by Geant4.
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The stepMax command provides an additionnal control of the step size of
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the multiple scattering.
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## HISTOGRAMS
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The test contains 16 built-in 1D histograms, which are managed by the
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HistoManager class and its Messenger. The histos can be individually
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activated with the command :
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```
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/analysis/h1/set id nbBins valMin valMax unit
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```
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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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```
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/analysis/h1/set id nbBins valMin valMax unit
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```
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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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```
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/analysis/setFileName name (default testem15)
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```
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It is possible to choose the format of the histogram file : root (default),
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hdf5, xml, csv, by changing the default file type in HistoManager.cc
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It is also possible to print selected histograms on an ascii file:
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```
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/analysis/h1/setAscii id
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```
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All selected histos will be written on a file name.ascii (default testem15)
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## VISUALIZATION
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The Visualization Manager is set in the main().
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The initialisation of the drawing is done via the commands
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/vis/... in the macro vis.mac. To get visualisation:
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```
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> /control/execute vis.mac
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```
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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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## HOW TO START ?
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- Execute TestEm15 in 'batch' mode from macro files:
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```
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% ./TestEm15 compt.mac
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```
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- Execute TestEm15 in 'interactive mode' with visualization:
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```
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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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```
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## - MACROS
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The examples of macros for Multiple Scattering:
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- electron.mac
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- muon.mac
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- 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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\subpage ExampleTestEm15_GC
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\page ExampleTestEm15_GC Example TestEm15 - Gamma Conversion
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## Gamma Conversion macros:
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- gamma.mac - tests of the 5D gamma -> e+ e- conversion model G4BetheHeitler5DModel
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All discrete processes are inactivated (see macro),
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so Gamma Conversion is 'forced'.
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## HISTOGRAMS for gamma conversion
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- 10 : Open Angle (rad)* E gamma (MeV).
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The most probable value of the e+ e- pair opening angle multiplied by the
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photon energy is 1.6 rad*MeV and 338 rad*MeV in case mu+ mu- pair.
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See: Olsen, Phys. Rev. 131 (1963) 406.
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See also: Fig. 7 of arXiv:1802.08253 and Fig. 6 arXiv:1910.12501.
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- 11 : Log10 ( recoil momentum).
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The distribution of the recoil momentum is described by
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Jost, Phys. Rev. 80 (1950) 189 (no form factor).
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See also Fig. 2 of Astroparticle Physics 88 (2017) 60.
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- 12 : Phi recoil.
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- 13 : Phi positron.
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For linearly polarized incident photons, the distributions should show
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a sinusoidal shape with period 180°, for non polarized incident photons,
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the distribution of azimuthal angles should be flat.
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- 14 : Asymmetry 2 * cos(phi_+ + phi_-).
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For a photon propagating along x, polarized along y,
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the average value of ( 2.0 * cos(phi_+ + phi_-) ),
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provides a measurement of the polarization asymmetry, A.
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Eq. (12) of Nucl. Instrum. Meth. A 729 (2013) 765
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The azimuthal angle of the event defined as the bisector angle
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of the azimuthal angles of the positron and of the electron,
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(phi_+ + phi_-)/2,
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provides the optimal measurement of the asymmetry
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Astroparticle Physics 88 (2017) 30.
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For high-energy photons (E >> 20 MeV), the asymptotic expression for A
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can be used for comparison.
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Boldyshev, Yad. Fiz. 14 (1971) 1027, Sov.J.Nucl.Phys. 14 (1972) 576.
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See also eq. (13) of arXiv:1802.08253
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Example : A ~ 0.17 at 100 GeV.
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- 15 : E plus / E gamma.
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x_+ = E plus / E gamma has a more-or-less flat spectrum that extends
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almost from 0. to 1.
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See Fig. 16 page 261 of "The Quantum Theory of Radiation", W. Heitler,
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3rd edition, 1954.
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- 16 : Phi of Gamma Polarization.
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The phi of polarization vector after transformation into reference system
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defined by gamma direction (z) , gamma polarization (x).
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## UI COMMANDS
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There are two commands to control G4BetheHeitler5DModel:
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```
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/process/gconv/conversionType itype
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/process/gconv/onIsolated bool
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```
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The command:
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```
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/process/gconv/conversionType
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```
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Allow to force conversion on nuclear or electron
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The parameter values:
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- 0 - (default) both triplet and nuclear conversion in proportion triplet/nuclear 1/Z
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- 1 - force nuclear conversion
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- 2 - force triplet
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The command:
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```
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/process/gconv/onIsolated
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```
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Allow simulate conversion on isolated particles without screening
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The perimeter values:
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- false - (default) atomic electron screening
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- true - conversion on isolated particles
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