PIONEER Beamline Simulations

Intro to G4beamline

The PIONEER beamline simulation is built using G4beamline (G4BL), a free open-source toolkit built on top of GEANT4. The latests (3.06) source and prebuilt binaries can be downloaded from here. Included in the download is the comprehensive user's guide (G4beamlineUsersGuide.pdf) that is immensely useful when getting started.

An overview guide for the PIONEER simulation is available here.

Every G4beamline simulation script needs at minimum a physics definition and beam definition. Beyond that, the user can define their own parameters using the param keyword along with the -unset option to allow the param to be overriden later in the script. Users can also build assets using predefined devices or custom boolean geometries and place these in the world using the place command.

The πE5 beamline in G4beamline

The πE5 simulation in G4BL was originially developed for the Mu3e Compact Muon Beam Line (CMBL), and has been modified for use in the MEGII experiment, and now for the PIONEER experiment. The magenetic elements in the simulation (quadrupoles, dipoles, sextupoles) rely on either existing field maps or calculations from geometry and coil windings. The QSK and HSC elements do not have field maps, and the QSF elements use the QSM field map.

The simulation relies on several pre-defined files in the original piE5 simultion.

Using the HiMB Pion Production Model

The HiMB Pion Production Model implemtents a parameterized production cross section the details of which are described here. G4Beamline must be built from source and the GEANT4 and G4Beamline source modification must be applied before building. The HiMB model source code is available here.

The model can be enabled through the physics command in G4BL.

The model also provides a mechanism for biasing or splitting pions to generate a larger sample of pions and muons produced from proton interactions in the production target. This splitting can be enabled by the following command in the G4BL script:

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