The user can create custom parameters in the user geometry class to modify parameters at runtime. See the geometry template for an example on how to add custom parameters. Additional information is provided in the section "Geometry and physics".
For example, to set the default production cut in the `OPTPhys` class:
`OPTPhys.DEFAULT.CUT = 0.001`
For a detailed explanation of the physics classes available in BoGEMMS-HPC, see the [Physics](./doc/physics.md) section.