At the beginning of prcoessing, the event contains primary particles which are pushed into a stack. The G4Event has the following objects at the end of its processing or when the stack becomes empty:
List of primary vertexes and particles
Trajectory collection (optional)
Hits Collection
Digits Collection (optional)
G4 Tracks
Tracks are made of three layers of class objects
G4Track
Position, Volume, Track Length, global ToF
ID of itself and mother track
G4DynamicParticle
Momentum, Energy, local time, polarization
Pre-fix decay channel
G4ParticleDefinition
Shared by all G4DynamicParticle of same type
Mass, lifetime, charge, other physical quantities
Decay Table
Tracks are deleted when:
it goes out of the world volume
it disappears (a decay)
it goes down to zero kinetic energy and no “at rest” additional process is required
the user decides to kill it
Step
Step has two points and is limitted by the volume boundary. The end point physically stands on the boundary, and it logically belongs to the next volume.