Contact : M.Asai (SLAC)

Introduction

This example demonstrates how to define a layered mass geometry in parallel world. In the mass (tracking) world, there are two boxes only. One is the world volume and the other is a box in the world. They both are made of air. Thus, if tracks do not see materials (water and lead) defined in the parallel world, they rarely interact. In the parallel world, there are boxes made of water and lead.

Geometry

RE04DetectorConstruction defines the mass (tracking) geometry. It firstly defines all materials which apear either in mass world or parallel world. Then in SetupGeometry() method, it defines the world volume and a box named "phantom". Both boxes are made of air.

RE04ParallelWorldConstruction defines the parallel world. For a parallel world, solid, logical and physical volumes which represent parallel world must not be created here but should be taken through G4VUserParallelWorld::GetWorld() method which creates clones of solid, logical and physical volumes of the world volume of the mass world. Please note that this cloned logical volume of the parallel world volume does not have a valid pointer to aa material but null.

In the parallel world, if a logical volume has a valid material pointer, a track in this volume (precisely saying a physical volume which is made of this logical volume) will see the material defined in this logical volume, regardless of the material in the mass geometry. If a logical volume has a null material pointer, a track will see the ordinary material defined in the mass world.

RE04ParallelWorldConstruction defines one placement volume of box-shape, which is made of water, and a mother box (placement volume with null material pointer), which contains parameterized volumes. RE04ParallelWorldParam class defines a parameterization of the parameterized volume "paraPara", which represents two boxes at different locations and made of water and lead respectively.

Physics

RE04PhysicsList uses ordinary physics builders. It also defines G4ParallelWorldProcess which deals with the parallel world. This G4ParallelWorldProcess is an extension of G4ParallelWorldScoringProcess. If SetLayeredMaterialFlag() of this process class is invoked, in addition to taking care of sensitive detectors in the parallel world, it also takes care of layered mass geometry. If this set method is not invoked, it behaves exactly same as G4ParallelWorldScoringProcess. The constructor of G4ParallelWorldProcess takes the name of the parallel world physical volume as an argument.

G4ParallelWorldProcess may be associated only to some limited kinds of particle types. The parallel world is seen only bythe particles which have G4ParallelWorldProcess in their process manager objects. In this RE04 example G4ParallelWorldProcess is defined to all particle types except ChargedGeantino. Thus, if you shoot CargedGeantino, it won't see any volume boundary defined in the parallel world.

Macro files

The macro file "score.mac" defines a scoring mesh which covers the "Phantom" and scores energy deposition. It shoots 1000 primary particles (by default 10 GeV muon-). Though the mass world has only air, given tracks, both primary muons and secondary particles see water and lead defined in the parallel world, you will see the energy deposition is not evenly distributed.

User action classes

In the main () of RE04.cc, three user action classes, i.e. RE04EventAction, RE04TrackingAction and RE04SteppingAction, are commented out. By using RE04SteppingAction, you will see a material name which a track sees for each step. By using RE04EventAction and RE04TrackingAction, you will see the similar information for all trajectories of one event.