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Forum: Event and Track Management
Re: Question MuMultipleScattering not listed (Kendall)
Re: None Re: MuMultipleScattering not listed (Marc Verderi)
Re: None Re: MuMultipleScattering not listed (Kendall)
Date: 21 Jun, 2013
From: Michael H. Kelsey <Michael H. Kelsey>

On Fri, 21 Jun 2013 12:15:14 GMT, Kendall wrote:
> Thank you very much for your reply. I had seen before that when I set
> the verbosity high (to 4 as you suggest) that muMsc is invoked at each
> step (along with Transp, muIoni, muBrem, muPairProd). I suppose what I
> don't understand is what is meant by 'invoked'. My understanding of it
> was that these listed processes were called on as possible candidates
> for the process during that step but that only the step-limiting process
> was the one to occur. Your comment definitely suggests that this is the
> wrong way to look at it.
> 
> Could you clarify this for me a little bit? Or even point to a place in
> the user manual (or other literature) where I could find an explanation?

In the Application Developer's Guide, you'll want to look at the differences between "discrete" and "continuous" processes.

Multiple scattering is an example of a _continuous_ process. Whatever trajectory the particle is following in a step, a continuous process integrates some kind of physics all the way along the step. A continuous process does not (cannot!) limit a step; it just applies its particular physics during the particle's travel, which has already been limited by some other discrete process.

Multiple scattering integrates all of the not-explicitly-modelled tiny deflections along the particle's path, and applies a net change of direction at the end. Ionization energy-loss is another example: it sums up samples from the Bethe-Bloch equation in tiny dx*(dE/dx) steps within a full G4Step, and applies that total delta-E at the end of the G4Step.

Does that help to clarify things?

     -- Michael Kelsey

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1 None: Re: MuMultipleScattering not listed   (Kendall - 24 Jun, 2013)
(_ None: Re: MuMultipleScattering not listed   (Marc Verderi - 24 Jun, 2013)
(_ Idea: Re: MuMultipleScattering not listed   (Vladimir Ivanchenko - 24 Jun, 2013)
(_ None: Re: MuMultipleScattering not listed   (michel maire - 24 Jun, 2013)
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