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Forum: Documentation and Examples
Re: None Geant4 output
Date: 13 Jan, 2009
From: John Apostolakis <John Apostolakis>


I am not sure, but it seems that you would like to understand what the different stages are in Geant4 tracking - which is what is reported by the printout in your posting.

The output that you see shows the state of the track after two of the stages in which the tracking applies the effects of physics processes.

In the along step stage, the effect of interactions that occur between the start and just before the end point of the step is accumulated. Typically this is the continuous energy loss, which approximates many collisions in each one of which little energy is lost. Also an external magnetic (or electric or combined) field's effect will be applied during this step.

At the end of this stage the particle can be thought to have almost arrived at the end point (or PostStep point) of the current step.

During the application of PostStep actions, typically one process will occur. It is the process that had proposed the minimum step - and which as a result was responsible for limiting the current step. This process will propose a change in the state of the particle. The tracking will check whether the proposal is valid, and apply it.

In some cases more than one process can be scheduled to occur at the PostStep point. This is needed to resolve such things as reflection/refraction for optical photons, or the displacement of a track by multiple scattering (when another interaction could occur at that end point.)

I hope that this answers the question. John A.

P.S. Could you please give your name and affiliation.

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