Gabriele Cosmo
95 lines
3.1 KiB
Markdown
95 lines
3.1 KiB
Markdown
\page Exampledecayer6 Example decayer6
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This is an example of the external decayer implementation
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with PYTHIA6.
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The complete PYTHIA6 documentation can be found at:
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https://pythia.org/
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The PYTHIA6 external decayer was originally developed within
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the AliRoot framework, by Andreas Morsch (CERN). \n
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The dependence on the ALICE software was taken off
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by Christian Holm Christensen. \n
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The dependence on the Root framework and the integration in
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the Geant4 framework was done by Ivana Hrivnacova (IPN Orsay).
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<hr>
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The use of the external decayer is demonstrated with using the
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classes from common examples repository, see below their complete
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list.
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The G4Pythia6Decayer class provides the implementation of the
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G4VExternalDecayer interface with using PYTHIA6. In order
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to be able to use PYTHIA6, which is written in FORTRAN,
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a C++ interface class Pythia6 is provided. This class
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interfaces only the PYTHIA6 functions relevant to decay.
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The G4Pythia6Decayer is instantiated in the
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P6DExtDecayerPhysics::ConstructProcess() function where the external
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decayer is set to G4Decay process for all particles.
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To demonstrate the decay with external decayer,
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the B- meson is defined in ExG4PrimaryGeneratorAction01,
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as it has no own decay table defined within Geant4.
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With PYTHIA6, it is possible to force a selected decay
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type. This selection can be chosen interactively via
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the implemented Geant4 UI command:
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```
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/pythia6Decayer/forceDecayType decayType
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```
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where the available decay types are listed in the EDecayType
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enumaration.
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The classes Pythia6, G4Pythia6Decayer, G4Pythia6DecayerMessenger
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are independent from the example classes and can be reused
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in another user application.
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Installation:
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- 1. Download the PYTHIA6 source file from the PYTHIA web site:\n
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https://pythia.org/
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Note: The last tested version: 6.4.28
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- 2A. With CMake: Build pythia6 library
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For a convenience a CMake file for building Pythia6 library from
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the source is provided in
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examples/extended/eventgenerator/CMakeLists.txt.pythia6.
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Build the pythia6 library following the instructions in this file
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and then define the environment variables:
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```
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PYTHIA6 the path where pythia6 library is installed
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PYTHIA6_VERSION the pythia version
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```
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- 2B. With GNUmake: Define the environment variables: \n
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```
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PYTHIA6 the path to pythia-versionX.f source code
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PYTHIA6_VERSION the pythia version
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```
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e.g. If you download pythia-6.4.28.f.gz and unzip it in $HOME,
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then you have to set:
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```
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export PYTHIA6=$HOME
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export PYTHIA6_VERSION="6.4.28"
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```
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pythia6 will be then compiled together with example code.
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- 3. Compilation:\n
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Then the example is compiled in a standard way, see
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[How to build and run an example](../../html/README_HowToRun.html).
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Note that with GNUmake build, an additional step 'gmake setup' is
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needed before 'gmake'.
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- 4. Execution:
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```
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% ./pythia6_decayer pythia6_decayer.in
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```
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This example uses the following user action classes from the extended examples 'common'
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repository:
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- Common::DetectorConstruction
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- Common::GunPrimaryGeneratorAction
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