Example extensibleFactory

Author

R. Hatcher
Fermilab
(based on Hadr00 by V. Ivantchenko, CERN)

Examples in the physicslist category show the possible ways how to define a physics list from Geant4 physics constructors. This example demonstrates the usage of g4alt::G4PhysListFactory to build a concrete physics list.

Physics List can be defined by its name given by the -p argument of the of the run command or by the PHYSLIST environment variable.

   ./extensibleFactory -m my.macro [ -p QGSP_BERT ] \
        [ -v | --verbose ] [ -h | --help ]

By default, FTFP_BERT Physics List will be instantiated if -p argument is not set and the PHYSLIST environment variable is not defined. This is the system default, but can be overridden using the SetDefaultReferencePhysList() method on the factory (see the code).

The extensible factory allows users to define and register their own physics lists. This example shows the addtional a new list "MySpecialPhysList".

   ./extensibleFactory -m run.mac -p MySpecialPhysList

The extensible factory also allows for the extension of lists by adding (using "+" as a separator) or replacing (using "_" as a separator) specific physics constructors. These can be specified by pre-defining a short name (e.g. RADIO for G4RadioactiveDecayPhysics) or providing the full class name.

   ./extensibleFactory -m run.mac -p FTFP_BERT_EMX+G4OpticalPhysics+RADIO

uses the FTFP_BERT physics list as a base

• replaces the list's standard EM portion with G4EmStandardPhysics_option2 ( standard EMX extension )
• adds G4OpticalPhysics
• adds G4RadioactiveDecayPhysics (RADIO defined in code to map to this)

The same experimental setup is used for all examples in the physicslist category:

Detector description

The geometry (defined in the DetectorConstruction class) consists in a box of scintillator material (CsI) followed by a thin box of air (screen) which is used to simplify scoring.

Primary generator

The primary generator is defined with usage of G4ParticleGun. The default particle is proton which hits the box perpendicular to the input face. The type of the particle and its energy are set in the PrimaryGeneratorAction class, and can be changed via the G4 built-in commands of the G4ParticleGun class.

Scoring (ntuples)

The screen volume is associated with a sensitive detector, ScreenSD, which accounts the following particle properties:

• trackID
• particle PDG encoding
• particle kinetic energy
• particle X,Y position
• particle time

The scored quantities are filled in the Screen ntuple, which is defined using G4AnalysisManager in RunAction class. The ntuple is saved in a Root file, which name is set to be equal to the example name in main () function.

How to build

An additional step is needed when building the example with GNUmake due to using the extra shared directory:

 % cd path_to_example/example
 % gmake setup
 % gmake

This will copy the files from shared in the example include and src; to remove these files:

 % gmake clean_setup