Problem 1659

Summary:	Section 9.9.1 - 2BN bremsstrahlung cross-section has two apparent typos
Product:	Documentation	Reporter:	Gavin Poludniowski <gpoludniowski>
Component:	Physics Reference Manual	Assignee:	Vladimir.Ivantchenko
Status:	RESOLVED FIXED
Severity:	trivial	CC:	kelsey
Priority:	P5
Version:	10.0
Hardware:	All
OS:	All

Description Gavin Poludniowski 2014-07-22 11:31:29 CEST

The quoted 2BN cross-section is not exactly that of the reference (Koch and Motz). 

In the geant doc:
(1) We have a (2E_0^2-1) not (2E_0^2+1)
(2) We also have a 2-2(E_0^2-3EE_0+E^2) not 2-2(7E_0^2-3E*E_0+E^2)

I couldn't find any erratum associated with the K&M reference. This is probably just typos in the manual, as I think the cross-section ends up negative!

Comment 1 Michael Kelsey 2014-07-23 05:34:26 CEST

Thank you for this feedback!  I have forwarded this to our EM expert.

Comment 2 Gavin Poludniowski 2014-07-23 10:12:29 CEST

I looked at the reference of Koch and Motz (Gluckstern and Hull, Phys. Rev. 90: 1030, 1953) and that is the same as K&M (and therefore different to Geant4 Ref Man). I have coded both possibilities up and they do give numerically different results. Note that there seem to be several Geant publications that quote the same as the Ref Man.

GP

Comment 3 Michael Kelsey 2014-07-23 16:29:49 CEST

I have fixed this myself in the PRM (section electromagnetic/lowenergy/bremsstrahlung.tex).  I confirmed that the code in G4Generator2BN.cc has the correct expressions from Koch & Motz.

Comment 4 Vladimir.Ivantchenko 2014-07-23 17:18:00 CEST

Hi Mike,

Thank you for the fix.

Vladimir