Rule-of-thumb for cuts

Dear all,

Are there any rules-of-thumb when specifying the cuts for the Geant4 simulations? In my case I’m simulating monoenergetic electrons isotropically onto a geometry that contains a CCD (the target). I have performed two different sets of simulations: the first one with cuts 1um, and the second with cuts 10um. I always set the cuts via macros with “/run/setCut”.

The results look way more different than I expected. My CCD depth dimension equals ~50um, and therefore I didn’t want to set bigger cuts.

First question: Is it always better to use smaller cuts in order to have more precise results? Here I’m disregarding simulation time;
Second question: Should my approach be always to have cuts at least smaller than the dimensions of my target?

I would so much appreciate any feedbacks. Thank you in advance.


_Geant4 Version:_10_7_3
_Operating System:_GNU/Linux Debian 11
CMake Version:

Hello @leonardoghizoni ,

have a look at the documentation and see whether you can make sense of your results.



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Hi @leonardoghizoni ,

What Physics problem you are developing ? Cuts can be defined in regions of interest.
A slight explanation;
Assuming, an alpha particle enters in medium (G4_Air) what will be the total energy loss? Here cuts will not play an important role.
However, if you want to know recoils, or secondaries production say gamma, then you can use cuts on particle production in the region.
You can also use step limiter Physics to increase precision.

You can also look into the advice of @pico .


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Dear @drvijayraj ,

Thanks for the feedback.

My physics problem is to build a shielding efficiency curve for a CCD inside an instrument in space. For that, I’m performing simulations with monoenergetic electrons and retrieving area and volume fluxes, and deposited energy via Geant4’s primitive scorers. In the end, I’ll have a curve of normalised fluxes of electrons as a function of the primary monoenergetic electrons. See graph attached.

My question is if there are any rules to apply in terms of cuts or step limiters for a given simulation. Thank you for the help.