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Keywords: region cut
Forum: Physics List
Re: Question region cut (V. Grabski)
Date: 24 Oct, 2003
From: michel maire <michel maire>

User V. Grabski wrote:

>> Hello, I have a problem with region cut setting. For the cut 1.3 m the
>> energy thresholds calculations for the gamma is strange.
>> 
>> Index : 4     used in the geometry : Yes     recalculation needed : No
>>  Material : quartz
>>  Range cuts        :  gamma 1.3 m      e- 1.3 m      e+ 1.3 m
>>  Energy thresholds :  gamma 2.88022e+295 J      e- 1.01145 GeV    e+ 962.847 MeV
>>  Region(s) which use this couple :
>>     layer_0
>> 
>> What I can do to correct this? Thanks, Varlen

 It is not related to region, but to the range -> energy relation.

 For e-/e+ the relation is monotonic, and as big is the range, you can
 compute a corresponding energy. 
 (As you as seen in your case ~1 m -> ~1 GeV)

 For Gamma, the relation is no more monotonic, due to a small valley in
 the total cross section between the regions of Compton dominant and
 pair production dominant, and after the cross section is flat.
 Therefore if the cut in range, i.e. the Absoption length, is too big
 we set the energy to DBL_MAX. Of course, this will prevent any brems
 production.

 See PhysicsReferenceManual 
 -> electromagnetic/miscellaneous/conversion range-energy

 We can imagine some trick to overcome this situation. But it would be
 somewhat arbitrary. 

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