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Question Re: Why is change in KineE not equal to dEStep? 

Forum: Event and Track Management
Re: Question Why is change in KineE not equal to dEStep? (Neil Fazel)
Re: None Re: Why is change in KineE not equal to dEStep? (michel maire)
Date: 06 Sep, 2011
From: Neil Fazel <Neil Fazel>

On Tue, 06 Sep 2011 13:50:56 GMT, michel maire wrote:
> On Mon, 05 Sep 2011 15:23:18 GMT, Neil Fazel wrote:
> 
> > I'm using verbose tracking to print out the kinetic energy (KineE) and
> > total energy deposited (dEStep) at each step on a track. I see that
> > dEStep does not equal the change in KineE. For example, below you see
> > that for Step# 3, KineE has decreased to 159 MeV from 999 MeV, but
> > dEStep is only 4.73 keV. What happened to kinetic energy difference (840
> > MeV) and what does dEStep = 4.73 keV represent?
> > 
> > (This is for a 1 GeV e- passing through a 1 cm layer of Pb.)
> > 
> 
>  if you run with tracking/verbose 2, you will understand your ouput (I hope ...).
>  For the second part of the question, please read a minimum of documentation about  geant4, or any MC transport code in general ...
> 
>             Michel
> 

Thanks. What I understand from the verbose tracking output is that changes in the kinetic energy of the electron in lead are the sum of the energy imparted to secondary particles (gamma or delta rays) plus the value of dEStep, which is apparently the energy deposited in the detector. According to the Physics Ref. Manual, ch. 7.1,

"Any energy loss process must calculate the continuous and discrete energy loss in a material. Below a given energy threshold the energy loss is continuous and above it the energy loss is simulated by the explicit production of secondary particles - gammas, electrons, and positrons."

It occurred to me that dEStep represented the continuous energy loss, but then the paragraph above suggests that either the continuous (below cutoff) or the discrete (above cutoff) energy loss occurs during a given step, not both. It looks like I have both.

Neil

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